Merge branch 'master' of https://github.com/prometheus/prometheus into update_k8s

.promu.yml

@@ -12,11 +12,11 @@ build:
           path: ./cmd/promtool
     flags: -mod=vendor -a -tags netgo
     ldflags: |
-        -X {{repoPath}}/vendor/github.com/prometheus/common/version.Version={{.Version}}
-        -X {{repoPath}}/vendor/github.com/prometheus/common/version.Revision={{.Revision}}
-        -X {{repoPath}}/vendor/github.com/prometheus/common/version.Branch={{.Branch}}
-        -X {{repoPath}}/vendor/github.com/prometheus/common/version.BuildUser={{user}}@{{host}}
-        -X {{repoPath}}/vendor/github.com/prometheus/common/version.BuildDate={{date "20060102-15:04:05"}}
+        -X github.com/prometheus/common/version.Version={{.Version}}
+        -X github.com/prometheus/common/version.Revision={{.Revision}}
+        -X github.com/prometheus/common/version.Branch={{.Branch}}
+        -X github.com/prometheus/common/version.BuildUser={{user}}@{{host}}
+        -X github.com/prometheus/common/version.BuildDate={{date "20060102-15:04:05"}}
 tarball:
     files:
         - consoles

MAINTAINERS.md

@@ -1,6 +1,6 @@
 Maintainers of this repository with their focus areas:
 
 * Brian Brazil <brian.brazil@robustperception.io> @brian-brazil: Console templates; semantics of PromQL, service discovery, and relabeling.
-* Fabian Reinartz <fabian.reinartz@coreos.com> @fabxc: PromQL parsing and evaluation; implementation of retrieval, alert notification, and service discovery.
+* Fabian Reinartz <freinartz@google.com> @fabxc: PromQL parsing and evaluation; implementation of retrieval, alert notification, and service discovery.
 * Julius Volz <julius.volz@gmail.com> @juliusv: Remote storage integrations; web UI.
 

Makefile.common

@@ -175,9 +175,11 @@ common-docker-tag-latest:
 promu: $(PROMU)
 
 $(PROMU):
-	curl -s -L $(PROMU_URL) | tar -xvz -C /tmp
-	mkdir -v -p $(FIRST_GOPATH)/bin
-	cp -v /tmp/promu-$(PROMU_VERSION).$(GO_BUILD_PLATFORM)/promu $(PROMU)
+	$(eval PROMU_TMP := $(shell mktemp -d))
+	curl -s -L $(PROMU_URL) | tar -xvzf - -C $(PROMU_TMP)
+	mkdir -p $(FIRST_GOPATH)/bin
+	cp $(PROMU_TMP)/promu-$(PROMU_VERSION).$(GO_BUILD_PLATFORM)/promu $(FIRST_GOPATH)/bin/promu
+	rm -r $(PROMU_TMP)
 
 .PHONY: proto
 proto:

config/config.go

@@ -233,6 +233,9 @@ func (c *Config) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	// Do global overrides and validate unique names.
 	jobNames := map[string]struct{}{}
 	for _, scfg := range c.ScrapeConfigs {
+		if scfg == nil {
+			return fmt.Errorf("empty or null scrape config section")
+		}
 		// First set the correct scrape interval, then check that the timeout
 		// (inferred or explicit) is not greater than that.
 		if scfg.ScrapeInterval == 0 {
@@ -254,6 +257,16 @@ func (c *Config) UnmarshalYAML(unmarshal func(interface{}) error) error {
 		}
 		jobNames[scfg.JobName] = struct{}{}
 	}
+	for _, rwcfg := range c.RemoteWriteConfigs {
+		if rwcfg == nil {
+			return fmt.Errorf("empty or null remote write config section")
+		}
+	}
+	for _, rrcfg := range c.RemoteReadConfigs {
+		if rrcfg == nil {
+			return fmt.Errorf("empty or null remote read config section")
+		}
+	}
 	return nil
 }
 
@@ -360,6 +373,13 @@ func (c *ScrapeConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
 		return err
 	}
 
+	// The UnmarshalYAML method of ServiceDiscoveryConfig is not being called because it's not a pointer.
+	// We cannot make it a pointer as the parser panics for inlined pointer structs.
+	// Thus we just do its validation here.
+	if err := c.ServiceDiscoveryConfig.Validate(); err != nil {
+		return err
+	}
+
 	// Check for users putting URLs in target groups.
 	if len(c.RelabelConfigs) == 0 {
 		for _, tg := range c.ServiceDiscoveryConfig.StaticConfigs {
@@ -371,6 +391,17 @@ func (c *ScrapeConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
 		}
 	}
 
+	for _, rlcfg := range c.RelabelConfigs {
+		if rlcfg == nil {
+			return fmt.Errorf("empty or null target relabeling rule in scrape config")
+		}
+	}
+	for _, rlcfg := range c.MetricRelabelConfigs {
+		if rlcfg == nil {
+			return fmt.Errorf("empty or null metric relabeling rule in scrape config")
+		}
+	}
+
 	// Add index to the static config target groups for unique identification
 	// within scrape pool.
 	for i, tg := range c.ServiceDiscoveryConfig.StaticConfigs {
@@ -392,7 +423,16 @@ func (c *AlertingConfig) UnmarshalYAML(unmarshal func(interface{}) error) error
 	// by the default due to the YAML parser behavior for empty blocks.
 	*c = AlertingConfig{}
 	type plain AlertingConfig
-	return unmarshal((*plain)(c))
+	if err := unmarshal((*plain)(c)); err != nil {
+		return err
+	}
+
+	for _, rlcfg := range c.AlertRelabelConfigs {
+		if rlcfg == nil {
+			return fmt.Errorf("empty or null alert relabeling rule")
+		}
+	}
+	return nil
 }
 
 // AlertmanagerConfig configures how Alertmanagers can be discovered and communicated with.
@@ -429,6 +469,13 @@ func (c *AlertmanagerConfig) UnmarshalYAML(unmarshal func(interface{}) error) er
 		return err
 	}
 
+	// The UnmarshalYAML method of ServiceDiscoveryConfig is not being called because it's not a pointer.
+	// We cannot make it a pointer as the parser panics for inlined pointer structs.
+	// Thus we just do its validation here.
+	if err := c.ServiceDiscoveryConfig.Validate(); err != nil {
+		return err
+	}
+
 	// Check for users putting URLs in target groups.
 	if len(c.RelabelConfigs) == 0 {
 		for _, tg := range c.ServiceDiscoveryConfig.StaticConfigs {
@@ -440,6 +487,12 @@ func (c *AlertmanagerConfig) UnmarshalYAML(unmarshal func(interface{}) error) er
 		}
 	}
 
+	for _, rlcfg := range c.RelabelConfigs {
+		if rlcfg == nil {
+			return fmt.Errorf("empty or null Alertmanager target relabeling rule")
+		}
+	}
+
 	// Add index to the static config target groups for unique identification
 	// within scrape pool.
 	for i, tg := range c.ServiceDiscoveryConfig.StaticConfigs {
@@ -632,6 +685,11 @@ func (c *RemoteWriteConfig) UnmarshalYAML(unmarshal func(interface{}) error) err
 	if c.URL == nil {
 		return fmt.Errorf("url for remote_write is empty")
 	}
+	for _, rlcfg := range c.WriteRelabelConfigs {
+		if rlcfg == nil {
+			return fmt.Errorf("empty or null relabeling rule in remote write config")
+		}
+	}
 
 	// The UnmarshalYAML method of HTTPClientConfig is not being called because it's not a pointer.
 	// We cannot make it a pointer as the parser panics for inlined pointer structs.

config/config_test.go

@@ -751,6 +751,58 @@ var expectedErrors = []struct {
 		filename: "section_key_dup.bad.yml",
 		errMsg:   "field scrape_configs already set in type config.plain",
 	},
+	{
+		filename: "azure_client_id_missing.bad.yml",
+		errMsg:   "Azure SD configuration requires a client_id",
+	},
+	{
+		filename: "azure_client_secret_missing.bad.yml",
+		errMsg:   "Azure SD configuration requires a client_secret",
+	},
+	{
+		filename: "azure_subscription_id_missing.bad.yml",
+		errMsg:   "Azure SD configuration requires a subscription_id",
+	},
+	{
+		filename: "azure_tenant_id_missing.bad.yml",
+		errMsg:   "Azure SD configuration requires a tenant_id",
+	},
+	{
+		filename: "empty_scrape_config.bad.yml",
+		errMsg:   "empty or null scrape config section",
+	},
+	{
+		filename: "empty_rw_config.bad.yml",
+		errMsg:   "empty or null remote write config section",
+	},
+	{
+		filename: "empty_rr_config.bad.yml",
+		errMsg:   "empty or null remote read config section",
+	},
+	{
+		filename: "empty_target_relabel_config.bad.yml",
+		errMsg:   "empty or null target relabeling rule",
+	},
+	{
+		filename: "empty_metric_relabel_config.bad.yml",
+		errMsg:   "empty or null metric relabeling rule",
+	},
+	{
+		filename: "empty_alert_relabel_config.bad.yml",
+		errMsg:   "empty or null alert relabeling rule",
+	},
+	{
+		filename: "empty_alertmanager_relabel_config.bad.yml",
+		errMsg:   "empty or null Alertmanager target relabeling rule",
+	},
+	{
+		filename: "empty_rw_relabel_config.bad.yml",
+		errMsg:   "empty or null relabeling rule in remote write config",
+	},
+	{
+		filename: "empty_static_config.bad.yml",
+		errMsg:   "empty or null section in static_configs",
+	},
 }
 
 func TestBadConfigs(t *testing.T) {

config/testdata/azure_client_id_missing.bad.yml

@@ -0,0 +1,7 @@
+scrape_configs:
+  - job_name: azure
+    azure_sd_configs:
+      - subscription_id: 11AAAA11-A11A-111A-A111-1111A1111A11
+        tenant_id: BBBB222B-B2B2-2B22-B222-2BB2222BB2B2
+        client_id:
+        client_secret: mysecret

config/testdata/azure_client_secret_missing.bad.yml

@@ -0,0 +1,7 @@
+scrape_configs:
+  - job_name: azure
+    azure_sd_configs:
+      - subscription_id: 11AAAA11-A11A-111A-A111-1111A1111A11
+        tenant_id: BBBB222B-B2B2-2B22-B222-2BB2222BB2B2
+        client_id: 333333CC-3C33-3333-CCC3-33C3CCCCC33C
+        client_secret:

config/testdata/azure_subscription_id_missing.bad.yml

@@ -0,0 +1,7 @@
+scrape_configs:
+  - job_name: azure
+    azure_sd_configs:
+      - subscription_id:
+        tenant_id: BBBB222B-B2B2-2B22-B222-2BB2222BB2B2
+        client_id: 333333CC-3C33-3333-CCC3-33C3CCCCC33C
+        client_secret: mysecret

config/testdata/azure_tenant_id_missing.bad.yml

@@ -0,0 +1,7 @@
+scrape_configs:
+  - job_name: azure
+    azure_sd_configs:
+      - subscription_id: 11AAAA11-A11A-111A-A111-1111A1111A11
+        tenant_id:
+        client_id: 333333CC-3C33-3333-CCC3-33C3CCCCC33C
+        client_secret: mysecret

config/testdata/empty_alert_relabel_config.bad.yml

@@ -0,0 +1,3 @@
+alerting:
+  alert_relabel_configs:
+  -

config/testdata/empty_alertmanager_relabel_config.bad.yml

@@ -0,0 +1,4 @@
+alerting:
+  alertmanagers:
+  - relabel_configs:
+    -

config/testdata/empty_metric_relabel_config.bad.yml

@@ -0,0 +1,4 @@
+scrape_configs:
+- job_name: "test"
+  metric_relabel_configs:
+  -

config/testdata/empty_rr_config.bad.yml

@@ -0,0 +1,2 @@
+remote_read:
+-

config/testdata/empty_rw_config.bad.yml

@@ -0,0 +1,2 @@
+remote_write:
+-

config/testdata/empty_rw_relabel_config.bad.yml

@@ -0,0 +1,4 @@
+remote_write:
+  - url: "foo"
+    write_relabel_configs:
+      -

config/testdata/empty_scrape_config.bad.yml

@@ -0,0 +1,2 @@
+scrape_configs:
+-

config/testdata/empty_static_config.bad.yml

@@ -0,0 +1,4 @@
+scrape_configs:
+- job_name: "test"
+  static_configs:
+  -

config/testdata/empty_target_relabel_config.bad.yml

@@ -0,0 +1,4 @@
+scrape_configs:
+- job_name: "test"
+  relabel_configs:
+  -

discovery/azure/azure.go

@@ -47,6 +47,7 @@ const (
 	azureLabelMachinePrivateIP     = azureLabel + "machine_private_ip"
 	azureLabelMachineTag           = azureLabel + "machine_tag_"
 	azureLabelMachineScaleSet      = azureLabel + "machine_scale_set"
+	azureLabelPowerState           = azureLabel + "machine_power_state"
 )
 
 var (
@@ -80,6 +81,13 @@ type SDConfig struct {
 	RefreshInterval model.Duration     `yaml:"refresh_interval,omitempty"`
 }
 
+func validateAuthParam(param, name string) error {
+	if len(param) == 0 {
+		return fmt.Errorf("Azure SD configuration requires a %s", name)
+	}
+	return nil
+}
+
 // UnmarshalYAML implements the yaml.Unmarshaler interface.
 func (c *SDConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	*c = DefaultSDConfig
@@ -88,8 +96,17 @@ func (c *SDConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	if err != nil {
 		return err
 	}
-	if c.SubscriptionID == "" {
-		return fmt.Errorf("Azure SD configuration requires a subscription_id")
+	if err = validateAuthParam(c.SubscriptionID, "subscription_id"); err != nil {
+		return err
+	}
+	if err = validateAuthParam(c.TenantID, "tenant_id"); err != nil {
+		return err
+	}
+	if err = validateAuthParam(c.ClientID, "client_id"); err != nil {
+		return err
+	}
+	if err = validateAuthParam(string(c.ClientSecret), "client_secret"); err != nil {
+		return err
 	}
 	return nil
 }
@@ -212,6 +229,7 @@ type virtualMachine struct {
 	ScaleSet       string
 	Tags           map[string]*string
 	NetworkProfile compute.NetworkProfile
+	PowerStateCode string
 }
 
 // Create a new azureResource object from an ID string.
@@ -286,12 +304,21 @@ func (d *Discovery) refresh() (tg *targetgroup.Group, err error) {
 				return
 			}
 
+			// We check if the virtual machine has been deallocated.
+			// If so, we skip them in service discovery.
+			if strings.EqualFold(vm.PowerStateCode, "PowerState/deallocated") {
+				level.Debug(d.logger).Log("msg", "Skipping virtual machine", "machine", vm.Name, "power_state", vm.PowerStateCode)
+				ch <- target{}
+				return
+			}
+
 			labels := model.LabelSet{
 				azureLabelMachineID:            model.LabelValue(vm.ID),
 				azureLabelMachineName:          model.LabelValue(vm.Name),
 				azureLabelMachineOSType:        model.LabelValue(vm.OsType),
 				azureLabelMachineLocation:      model.LabelValue(vm.Location),
 				azureLabelMachineResourceGroup: model.LabelValue(r.ResourceGroup),
+				azureLabelPowerState:           model.LabelValue(vm.PowerStateCode),
 			}
 
 			if vm.ScaleSet != "" {
@@ -319,16 +346,6 @@ func (d *Discovery) refresh() (tg *targetgroup.Group, err error) {
 					continue
 				}
 
-				// Unfortunately Azure does not return information on whether a VM is deallocated.
-				// This information is available via another API call however the Go SDK does not
-				// yet support this. On deallocated machines, this value happens to be nil so it
-				// is a cheap and easy way to determine if a machine is allocated or not.
-				if networkInterface.Properties.Primary == nil {
-					level.Debug(d.logger).Log("msg", "Skipping deallocated virtual machine", "machine", vm.Name)
-					ch <- target{}
-					return
-				}
-
 				if *networkInterface.Properties.Primary {
 					for _, ip := range *networkInterface.Properties.IPConfigurations {
 						if ip.Properties.PrivateIPAddress != nil {
@@ -456,6 +473,7 @@ func mapFromVM(vm compute.VirtualMachine) virtualMachine {
 		ScaleSet:       "",
 		Tags:           tags,
 		NetworkProfile: *(vm.Properties.NetworkProfile),
+		PowerStateCode: getPowerStateFromVMInstanceView(vm.Properties.InstanceView),
 	}
 }
 
@@ -476,6 +494,7 @@ func mapFromVMScaleSetVM(vm compute.VirtualMachineScaleSetVM, scaleSetName strin
 		ScaleSet:       scaleSetName,
 		Tags:           tags,
 		NetworkProfile: *(vm.Properties.NetworkProfile),
+		PowerStateCode: getPowerStateFromVMInstanceView(vm.Properties.InstanceView),
 	}
 }
 
@@ -508,3 +527,16 @@ func (client *azureClient) getNetworkInterfaceByID(networkInterfaceID string) (n
 
 	return result, nil
 }
+
+func getPowerStateFromVMInstanceView(instanceView *compute.VirtualMachineInstanceView) (powerState string) {
+	if instanceView.Statuses == nil {
+		return
+	}
+	for _, ivs := range *instanceView.Statuses {
+		code := *(ivs.Code)
+		if strings.HasPrefix(code, "PowerState") {
+			powerState = code
+		}
+	}
+	return
+}

discovery/azure/azure_test.go

@@ -26,6 +26,10 @@ func TestMapFromVMWithEmptyTags(t *testing.T) {
 	vmType := "type"
 	location := "westeurope"
 	networkProfile := compute.NetworkProfile{}
+	provisioningStatusCode := "ProvisioningState/succeeded"
+	provisionDisplayStatus := "Provisioning succeeded"
+	powerStatusCode := "PowerState/running"
+	powerDisplayStatus := "VM running"
 	properties := &compute.VirtualMachineProperties{
 		StorageProfile: &compute.StorageProfile{
 			OsDisk: &compute.OSDisk{
@@ -33,6 +37,20 @@ func TestMapFromVMWithEmptyTags(t *testing.T) {
 			},
 		},
 		NetworkProfile: &networkProfile,
+		InstanceView: &compute.VirtualMachineInstanceView{
+			Statuses: &[]compute.InstanceViewStatus{
+				{
+					Code:          &provisioningStatusCode,
+					Level:         "Info",
+					DisplayStatus: &provisionDisplayStatus,
+				},
+				{
+					Code:          &powerStatusCode,
+					Level:         "Info",
+					DisplayStatus: &powerDisplayStatus,
+				},
+			},
+		},
 	}
 
 	testVM := compute.VirtualMachine{
@@ -52,6 +70,7 @@ func TestMapFromVMWithEmptyTags(t *testing.T) {
 		OsType:         "Linux",
 		Tags:           map[string]*string{},
 		NetworkProfile: networkProfile,
+		PowerStateCode: "PowerState/running",
 	}
 
 	actualVM := mapFromVM(testVM)
@@ -69,6 +88,10 @@ func TestMapFromVMWithTags(t *testing.T) {
 	tags := map[string]*string{
 		"prometheus": new(string),
 	}
+	provisioningStatusCode := "ProvisioningState/succeeded"
+	provisionDisplayStatus := "Provisioning succeeded"
+	powerStatusCode := "PowerState/running"
+	powerDisplayStatus := "VM running"
 	networkProfile := compute.NetworkProfile{}
 	properties := &compute.VirtualMachineProperties{
 		StorageProfile: &compute.StorageProfile{
@@ -77,6 +100,20 @@ func TestMapFromVMWithTags(t *testing.T) {
 			},
 		},
 		NetworkProfile: &networkProfile,
+		InstanceView: &compute.VirtualMachineInstanceView{
+			Statuses: &[]compute.InstanceViewStatus{
+				{
+					Code:          &provisioningStatusCode,
+					Level:         "Info",
+					DisplayStatus: &provisionDisplayStatus,
+				},
+				{
+					Code:          &powerStatusCode,
+					Level:         "Info",
+					DisplayStatus: &powerDisplayStatus,
+				},
+			},
+		},
 	}
 
 	testVM := compute.VirtualMachine{
@@ -96,6 +133,7 @@ func TestMapFromVMWithTags(t *testing.T) {
 		OsType:         "Linux",
 		Tags:           tags,
 		NetworkProfile: networkProfile,
+		PowerStateCode: "PowerState/running",
 	}
 
 	actualVM := mapFromVM(testVM)
@@ -111,6 +149,10 @@ func TestMapFromVMScaleSetVMWithEmptyTags(t *testing.T) {
 	vmType := "type"
 	location := "westeurope"
 	networkProfile := compute.NetworkProfile{}
+	provisioningStatusCode := "ProvisioningState/succeeded"
+	provisionDisplayStatus := "Provisioning succeeded"
+	powerStatusCode := "PowerState/running"
+	powerDisplayStatus := "VM running"
 	properties := &compute.VirtualMachineScaleSetVMProperties{
 		StorageProfile: &compute.StorageProfile{
 			OsDisk: &compute.OSDisk{
@@ -118,6 +160,20 @@ func TestMapFromVMScaleSetVMWithEmptyTags(t *testing.T) {
 			},
 		},
 		NetworkProfile: &networkProfile,
+		InstanceView: &compute.VirtualMachineInstanceView{
+			Statuses: &[]compute.InstanceViewStatus{
+				{
+					Code:          &provisioningStatusCode,
+					Level:         "Info",
+					DisplayStatus: &provisionDisplayStatus,
+				},
+				{
+					Code:          &powerStatusCode,
+					Level:         "Info",
+					DisplayStatus: &powerDisplayStatus,
+				},
+			},
+		},
 	}
 
 	testVM := compute.VirtualMachineScaleSetVM{
@@ -139,6 +195,7 @@ func TestMapFromVMScaleSetVMWithEmptyTags(t *testing.T) {
 		Tags:           map[string]*string{},
 		NetworkProfile: networkProfile,
 		ScaleSet:       scaleSet,
+		PowerStateCode: "PowerState/running",
 	}
 
 	actualVM := mapFromVMScaleSetVM(testVM, scaleSet)
@@ -157,6 +214,10 @@ func TestMapFromVMScaleSetVMWithTags(t *testing.T) {
 		"prometheus": new(string),
 	}
 	networkProfile := compute.NetworkProfile{}
+	provisioningStatusCode := "ProvisioningState/succeeded"
+	provisionDisplayStatus := "Provisioning succeeded"
+	powerStatusCode := "PowerState/running"
+	powerDisplayStatus := "VM running"
 	properties := &compute.VirtualMachineScaleSetVMProperties{
 		StorageProfile: &compute.StorageProfile{
 			OsDisk: &compute.OSDisk{
@@ -164,6 +225,20 @@ func TestMapFromVMScaleSetVMWithTags(t *testing.T) {
 			},
 		},
 		NetworkProfile: &networkProfile,
+		InstanceView: &compute.VirtualMachineInstanceView{
+			Statuses: &[]compute.InstanceViewStatus{
+				{
+					Code:          &provisioningStatusCode,
+					Level:         "Info",
+					DisplayStatus: &provisionDisplayStatus,
+				},
+				{
+					Code:          &powerStatusCode,
+					Level:         "Info",
+					DisplayStatus: &powerDisplayStatus,
+				},
+			},
+		},
 	}
 
 	testVM := compute.VirtualMachineScaleSetVM{
@@ -185,6 +260,7 @@ func TestMapFromVMScaleSetVMWithTags(t *testing.T) {
 		Tags:           tags,
 		NetworkProfile: networkProfile,
 		ScaleSet:       scaleSet,
+		PowerStateCode: "PowerState/running",
 	}
 
 	actualVM := mapFromVMScaleSetVM(testVM, scaleSet)
@@ -193,3 +269,52 @@ func TestMapFromVMScaleSetVMWithTags(t *testing.T) {
 		t.Errorf("Expected %v got %v", expectedVM, actualVM)
 	}
 }
+
+func TestGetPowerStatusFromVM(t *testing.T) {
+	provisioningStatusCode := "ProvisioningState/succeeded"
+	provisionDisplayStatus := "Provisioning succeeded"
+	powerStatusCode := "PowerState/running"
+	powerDisplayStatus := "VM running"
+	properties := &compute.VirtualMachineScaleSetVMProperties{
+		StorageProfile: &compute.StorageProfile{
+			OsDisk: &compute.OSDisk{
+				OsType: "Linux",
+			},
+		},
+		InstanceView: &compute.VirtualMachineInstanceView{
+			Statuses: &[]compute.InstanceViewStatus{
+				{
+					Code:          &provisioningStatusCode,
+					Level:         "Info",
+					DisplayStatus: &provisionDisplayStatus,
+				},
+				{
+					Code:          &powerStatusCode,
+					Level:         "Info",
+					DisplayStatus: &powerDisplayStatus,
+				},
+			},
+		},
+	}
+
+	testVM := compute.VirtualMachineScaleSetVM{
+		Properties: properties,
+	}
+
+	actual := getPowerStateFromVMInstanceView(testVM.Properties.InstanceView)
+
+	expected := "PowerState/running"
+
+	if actual != expected {
+		t.Errorf("expected powerStatus %s, but got %s instead", expected, actual)
+	}
+
+	// Noq we test a virtualMachine with an empty InstanceView struct.
+	testVM.Properties.InstanceView = &compute.VirtualMachineInstanceView{}
+
+	actual = getPowerStateFromVMInstanceView(testVM.Properties.InstanceView)
+
+	if actual != "" {
+		t.Errorf("expected powerStatus %s, but got %s instead", expected, actual)
+	}
+}

discovery/config/config.go

@@ -14,6 +14,8 @@
 package config
 
 import (
+	"fmt"
+
 	"github.com/prometheus/prometheus/discovery/azure"
 	"github.com/prometheus/prometheus/discovery/consul"
 	"github.com/prometheus/prometheus/discovery/dns"
@@ -58,8 +60,67 @@ type ServiceDiscoveryConfig struct {
 	TritonSDConfigs []*triton.SDConfig `yaml:"triton_sd_configs,omitempty"`
 }
 
-// UnmarshalYAML implements the yaml.Unmarshaler interface.
-func (c *ServiceDiscoveryConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
-	type plain ServiceDiscoveryConfig
-	return unmarshal((*plain)(c))
+// Validate validates the ServiceDiscoveryConfig.
+func (c *ServiceDiscoveryConfig) Validate() error {
+	for _, cfg := range c.AzureSDConfigs {
+		if cfg == nil {
+			return fmt.Errorf("empty or null section in azure_sd_configs")
+		}
+	}
+	for _, cfg := range c.ConsulSDConfigs {
+		if cfg == nil {
+			return fmt.Errorf("empty or null section in consul_sd_configs")
+		}
+	}
+	for _, cfg := range c.DNSSDConfigs {
+		if cfg == nil {
+			return fmt.Errorf("empty or null section in dns_sd_configs")
+		}
+	}
+	for _, cfg := range c.EC2SDConfigs {
+		if cfg == nil {
+			return fmt.Errorf("empty or null section in ec2_sd_configs")
+		}
+	}
+	for _, cfg := range c.FileSDConfigs {
+		if cfg == nil {
+			return fmt.Errorf("empty or null section in file_sd_configs")
+		}
+	}
+	for _, cfg := range c.GCESDConfigs {
+		if cfg == nil {
+			return fmt.Errorf("empty or null section in gce_sd_configs")
+		}
+	}
+	for _, cfg := range c.KubernetesSDConfigs {
+		if cfg == nil {
+			return fmt.Errorf("empty or null section in kubernetes_sd_configs")
+		}
+	}
+	for _, cfg := range c.MarathonSDConfigs {
+		if cfg == nil {
+			return fmt.Errorf("empty or null section in marathon_sd_configs")
+		}
+	}
+	for _, cfg := range c.NerveSDConfigs {
+		if cfg == nil {
+			return fmt.Errorf("empty or null section in nerve_sd_configs")
+		}
+	}
+	for _, cfg := range c.OpenstackSDConfigs {
+		if cfg == nil {
+			return fmt.Errorf("empty or null section in openstack_sd_configs")
+		}
+	}
+	for _, cfg := range c.ServersetSDConfigs {
+		if cfg == nil {
+			return fmt.Errorf("empty or null section in serverset_sd_configs")
+		}
+	}
+	for _, cfg := range c.StaticConfigs {
+		if cfg == nil {
+			return fmt.Errorf("empty or null section in static_configs")
+		}
+	}
+	return nil
 }

discovery/ec2/ec2.go

@@ -46,6 +46,7 @@ const (
 	ec2LabelPlatform        = ec2Label + "platform"
 	ec2LabelPublicDNS       = ec2Label + "public_dns_name"
 	ec2LabelPublicIP        = ec2Label + "public_ip"
+	ec2LabelPrivateDNS      = ec2Label + "private_dns_name"
 	ec2LabelPrivateIP       = ec2Label + "private_ip"
 	ec2LabelPrimarySubnetID = ec2Label + "primary_subnet_id"
 	ec2LabelSubnetID        = ec2Label + "subnet_id"
@@ -250,6 +251,9 @@ func (d *Discovery) refresh() (tg *targetgroup.Group, err error) {
 				}
 
 				labels[ec2LabelPrivateIP] = model.LabelValue(*inst.PrivateIpAddress)
+				if inst.PrivateDnsName != nil {
+					labels[ec2LabelPrivateDNS] = model.LabelValue(*inst.PrivateDnsName)
+				}
 				addr := net.JoinHostPort(*inst.PrivateIpAddress, fmt.Sprintf("%d", d.port))
 				labels[model.AddressLabel] = model.LabelValue(addr)
 

discovery/manager.go

@@ -314,11 +314,13 @@ func (m *Manager) allGroups() map[string][]*targetgroup.Group {
 }
 
 func (m *Manager) registerProviders(cfg sd_config.ServiceDiscoveryConfig, setName string) {
+	var added bool
 	add := func(cfg interface{}, newDiscoverer func() (Discoverer, error)) {
 		t := reflect.TypeOf(cfg).String()
 		for _, p := range m.providers {
 			if reflect.DeepEqual(cfg, p.config) {
 				p.subs = append(p.subs, setName)
+				added = true
 				return
 			}
 		}
@@ -337,6 +339,7 @@ func (m *Manager) registerProviders(cfg sd_config.ServiceDiscoveryConfig, setNam
 			subs:   []string{setName},
 		}
 		m.providers = append(m.providers, &provider)
+		added = true
 	}
 
 	for _, c := range cfg.DNSSDConfigs {
@@ -401,7 +404,17 @@ func (m *Manager) registerProviders(cfg sd_config.ServiceDiscoveryConfig, setNam
 	}
 	if len(cfg.StaticConfigs) > 0 {
 		add(setName, func() (Discoverer, error) {
-			return &StaticProvider{cfg.StaticConfigs}, nil
+			return &StaticProvider{TargetGroups: cfg.StaticConfigs}, nil
+		})
+	}
+	if !added {
+		// Add an empty target group to force the refresh of the corresponding
+		// scrape pool and to notify the receiver that this target set has no
+		// current targets.
+		// It can happen because the combined set of SD configurations is empty
+		// or because we fail to instantiate all the SD configurations.
+		add(setName, func() (Discoverer, error) {
+			return &StaticProvider{TargetGroups: []*targetgroup.Group{&targetgroup.Group{}}}, nil
 		})
 	}
 }

discovery/manager_test.go

@@ -719,6 +719,7 @@ func assertEqualGroups(t *testing.T, got, expected []*targetgroup.Group, msg fun
 }
 
 func verifyPresence(t *testing.T, tSets map[poolKey]map[string]*targetgroup.Group, poolKey poolKey, label string, present bool) {
+	t.Helper()
 	if _, ok := tSets[poolKey]; !ok {
 		t.Fatalf("'%s' should be present in Pool keys: %v", poolKey, tSets)
 		return
@@ -741,7 +742,7 @@ func verifyPresence(t *testing.T, tSets map[poolKey]map[string]*targetgroup.Grou
 		if !present {
 			msg = "not"
 		}
-		t.Fatalf("'%s' should %s be present in Targets labels: %v", label, msg, mergedTargets)
+		t.Fatalf("%q should %s be present in Targets labels: %q", label, msg, mergedTargets)
 	}
 }
 
@@ -781,7 +782,7 @@ scrape_configs:
    - targets: ["foo:9090"]
 `
 	if err := yaml.UnmarshalStrict([]byte(sTwo), cfg); err != nil {
-		t.Fatalf("Unable to load YAML config sOne: %s", err)
+		t.Fatalf("Unable to load YAML config sTwo: %s", err)
 	}
 	c = make(map[string]sd_config.ServiceDiscoveryConfig)
 	for _, v := range cfg.ScrapeConfigs {
@@ -794,6 +795,67 @@ scrape_configs:
 	verifyPresence(t, discoveryManager.targets, poolKey{setName: "prometheus", provider: "string/0"}, "{__address__=\"bar:9090\"}", false)
 }
 
+// TestTargetSetRecreatesEmptyStaticConfigs ensures that reloading a config file after
+// removing all targets from the static_configs sends an update with empty targetGroups.
+// This is required to signal the receiver that this target set has no current targets.
+func TestTargetSetRecreatesEmptyStaticConfigs(t *testing.T) {
+	cfg := &config.Config{}
+
+	sOne := `
+scrape_configs:
+ - job_name: 'prometheus'
+   static_configs:
+   - targets: ["foo:9090"]
+`
+	if err := yaml.UnmarshalStrict([]byte(sOne), cfg); err != nil {
+		t.Fatalf("Unable to load YAML config sOne: %s", err)
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	discoveryManager := NewManager(ctx, log.NewNopLogger())
+	discoveryManager.updatert = 100 * time.Millisecond
+	go discoveryManager.Run()
+
+	c := make(map[string]sd_config.ServiceDiscoveryConfig)
+	for _, v := range cfg.ScrapeConfigs {
+		c[v.JobName] = v.ServiceDiscoveryConfig
+	}
+	discoveryManager.ApplyConfig(c)
+
+	<-discoveryManager.SyncCh()
+	verifyPresence(t, discoveryManager.targets, poolKey{setName: "prometheus", provider: "string/0"}, "{__address__=\"foo:9090\"}", true)
+
+	sTwo := `
+scrape_configs:
+ - job_name: 'prometheus'
+   static_configs:
+`
+	if err := yaml.UnmarshalStrict([]byte(sTwo), cfg); err != nil {
+		t.Fatalf("Unable to load YAML config sTwo: %s", err)
+	}
+	c = make(map[string]sd_config.ServiceDiscoveryConfig)
+	for _, v := range cfg.ScrapeConfigs {
+		c[v.JobName] = v.ServiceDiscoveryConfig
+	}
+	discoveryManager.ApplyConfig(c)
+
+	<-discoveryManager.SyncCh()
+
+	pkey := poolKey{setName: "prometheus", provider: "string/0"}
+	targetGroups, ok := discoveryManager.targets[pkey]
+	if !ok {
+		t.Fatalf("'%v' should be present in target groups", pkey)
+	}
+	group, ok := targetGroups[""]
+	if !ok {
+		t.Fatalf("missing '' key in target groups %v", targetGroups)
+	}
+
+	if len(group.Targets) != 0 {
+		t.Fatalf("Invalid number of targets: expected 0, got %d", len(group.Targets))
+	}
+}
+
 func TestIdenticalConfigurationsAreCoalesced(t *testing.T) {
 	tmpFile, err := ioutil.TempFile("", "sd")
 	if err != nil {

docs/configuration/configuration.md

@@ -263,10 +263,11 @@ The following meta labels are available on targets during relabeling:
 * `__meta_azure_machine_location`: the location the machine runs in
 * `__meta_azure_machine_name`: the machine name
 * `__meta_azure_machine_os_type`: the machine operating system
+* `__meta_azure_machine_power_state`: the current power state of the machine
 * `__meta_azure_machine_private_ip`: the machine's private IP
 * `__meta_azure_machine_resource_group`: the machine's resource group
-* `__meta_azure_machine_tag_<tagname>`: each tag value of the machine
 * `__meta_azure_machine_scale_set`: the name of the scale set which the vm is part of (this value is only set if you are using a [scale set](https://docs.microsoft.com/en-us/azure/virtual-machine-scale-sets/))
+* `__meta_azure_machine_tag_<tagname>`: each tag value of the machine
 
 See below for the configuration options for Azure discovery:
 
@@ -407,6 +408,7 @@ The following meta labels are available on targets during [relabeling](#relabel_
 * `__meta_ec2_owner_id`: the ID of the AWS account that owns the EC2 instance
 * `__meta_ec2_platform`: the Operating System platform, set to 'windows' on Windows servers, absent otherwise
 * `__meta_ec2_primary_subnet_id`: the subnet ID of the primary network interface, if available
+* `__meta_ec2_private_dns_name`: the private DNS name of the instance, if available
 * `__meta_ec2_private_ip`: the private IP address of the instance, if present
 * `__meta_ec2_public_dns_name`: the public DNS name of the instance, if available
 * `__meta_ec2_public_ip`: the public IP address of the instance, if available

docs/querying/api.md

@@ -24,6 +24,10 @@ and one of the following HTTP response codes:
 Other non-`2xx` codes may be returned for errors occurring before the API
 endpoint is reached.
 
+An array of warnings may be returned if there are errors that do
+not inhibit the request execution. All of the data that was successfully
+collected will be returned in the data field.
+
 The JSON response envelope format is as follows:
 
 ```
@@ -34,7 +38,11 @@ The JSON response envelope format is as follows:
   // Only set if status is "error". The data field may still hold
   // additional data.
   "errorType": "<string>",
-  "error": "<string>"
+  "error": "<string>",
+
+  // Only if there were warnings while executing the request.
+  // There will still be data in the data field.
+  "warnings": ["<string>"]
 }
 ```
 

documentation/examples/custom-sd/adapter/adapter.go

@@ -25,6 +25,7 @@ import (
 
 	"github.com/go-kit/kit/log"
 	"github.com/go-kit/kit/log/level"
+	"github.com/prometheus/common/model"
 	"github.com/prometheus/prometheus/discovery"
 	"github.com/prometheus/prometheus/discovery/targetgroup"
 )
@@ -34,6 +35,15 @@ type customSD struct {
 	Labels  map[string]string `json:"labels"`
 }
 
+func fingerprint(group *targetgroup.Group) model.Fingerprint {
+	groupFingerprint := model.LabelSet{}.Fingerprint()
+	for _, targets := range group.Targets {
+		groupFingerprint ^= targets.Fingerprint()
+	}
+	groupFingerprint ^= group.Labels.Fingerprint()
+	return groupFingerprint
+}
+
 // Adapter runs an unknown service discovery implementation and converts its target groups
 // to JSON and writes to a file for file_sd.
 type Adapter struct {
@@ -57,13 +67,7 @@ func mapToArray(m map[string]*customSD) []customSD {
 func generateTargetGroups(allTargetGroups map[string][]*targetgroup.Group) map[string]*customSD {
 	groups := make(map[string]*customSD)
 	for k, sdTargetGroups := range allTargetGroups {
-		for i, group := range sdTargetGroups {
-
-			// There is no target, so no need to keep it.
-			if len(group.Targets) <= 0 {
-				continue
-			}
-
+		for _, group := range sdTargetGroups {
 			newTargets := make([]string, 0)
 			newLabels := make(map[string]string)
 
@@ -76,12 +80,16 @@ func generateTargetGroups(allTargetGroups map[string][]*targetgroup.Group) map[s
 			for name, value := range group.Labels {
 				newLabels[string(name)] = string(value)
 			}
-			// Make a unique key, including the current index, in case the sd_type (map key) and group.Source is not unique.
-			key := fmt.Sprintf("%s:%s:%d", k, group.Source, i)
-			groups[key] = &customSD{
+
+			sdGroup := customSD{
+
 				Targets: newTargets,
 				Labels:  newLabels,
 			}
+			// Make a unique key, including group's fingerprint, in case the sd_type (map key) and group.Source is not unique.
+			groupFingerprint := fingerprint(group)
+			key := fmt.Sprintf("%s:%s:%s", k, group.Source, groupFingerprint.String())
+			groups[key] = &sdGroup
 		}
 	}
 

documentation/examples/custom-sd/adapter/adapter_test.go

@@ -41,7 +41,16 @@ func TestGenerateTargetGroups(t *testing.T) {
 					},
 				},
 			},
-			expectedCustomSD: map[string]*customSD{},
+			expectedCustomSD: map[string]*customSD{
+				"customSD:Consul:0000000000000000": {
+					Targets: []string{},
+					Labels:  map[string]string{},
+				},
+				"customSD:Kubernetes:0000000000000000": {
+					Targets: []string{},
+					Labels:  map[string]string{},
+				},
+			},
 		},
 		{
 			title: "targetGroup filled",
@@ -78,7 +87,7 @@ func TestGenerateTargetGroups(t *testing.T) {
 				},
 			},
 			expectedCustomSD: map[string]*customSD{
-				"customSD:Azure:0": {
+				"customSD:Azure:282a007a18fadbbb": {
 					Targets: []string{
 						"host1",
 						"host2",
@@ -87,7 +96,7 @@ func TestGenerateTargetGroups(t *testing.T) {
 						"__meta_test_label": "label_test_1",
 					},
 				},
-				"customSD:Openshift:1": {
+				"customSD:Openshift:281c007a18ea2ad0": {
 					Targets: []string{
 						"host3",
 						"host4",
@@ -125,7 +134,7 @@ func TestGenerateTargetGroups(t *testing.T) {
 				},
 			},
 			expectedCustomSD: map[string]*customSD{
-				"customSD:GCE:0": {
+				"customSD:GCE:282a007a18fadbbb": {
 					Targets: []string{
 						"host1",
 						"host2",
@@ -134,6 +143,12 @@ func TestGenerateTargetGroups(t *testing.T) {
 						"__meta_test_label": "label_test_1",
 					},
 				},
+				"customSD:Kubernetes:282e007a18fad483": {
+					Targets: []string{},
+					Labels: map[string]string{
+						"__meta_test_label": "label_test_2",
+					},
+				},
 			},
 		},
 	}

promql/ast.go

@@ -111,8 +111,9 @@ type MatrixSelector struct {
 	Offset        time.Duration
 	LabelMatchers []*labels.Matcher
 
-	// The series are populated at query preparation time.
-	series []storage.Series
+	// The unexpanded seriesSet populated at query preparation time.
+	unexpandedSeriesSet storage.SeriesSet
+	series              []storage.Series
 }
 
 // NumberLiteral represents a number.
@@ -144,8 +145,9 @@ type VectorSelector struct {
 	Offset        time.Duration
 	LabelMatchers []*labels.Matcher
 
-	// The series are populated at query preparation time.
-	series []storage.Series
+	// The unexpanded seriesSet populated at query preparation time.
+	unexpandedSeriesSet storage.SeriesSet
+	series              []storage.Series
 }
 
 func (e *AggregateExpr) Type() ValueType  { return ValueTypeVector }

promql/engine.go

@@ -154,8 +154,8 @@ func (q *query) Exec(ctx context.Context) *Result {
 		span.SetTag(queryTag, q.stmt.String())
 	}
 
-	res, err := q.ng.exec(ctx, q)
-	return &Result{Err: err, Value: res}
+	res, err, warnings := q.ng.exec(ctx, q)
+	return &Result{Err: err, Value: res, Warnings: warnings}
 }
 
 // contextDone returns an error if the context was canceled or timed out.
@@ -332,7 +332,7 @@ func (ng *Engine) newTestQuery(f func(context.Context) error) Query {
 //
 // At this point per query only one EvalStmt is evaluated. Alert and record
 // statements are not handled by the Engine.
-func (ng *Engine) exec(ctx context.Context, q *query) (Value, error) {
+func (ng *Engine) exec(ctx context.Context, q *query) (Value, error, storage.Warnings) {
 	ng.metrics.currentQueries.Inc()
 	defer ng.metrics.currentQueries.Dec()
 
@@ -345,7 +345,7 @@ func (ng *Engine) exec(ctx context.Context, q *query) (Value, error) {
 	queueSpanTimer, _ := q.stats.GetSpanTimer(ctx, stats.ExecQueueTime, ng.metrics.queryQueueTime)
 
 	if err := ng.gate.Start(ctx); err != nil {
-		return nil, contextErr(err, "query queue")
+		return nil, contextErr(err, "query queue"), nil
 	}
 	defer ng.gate.Done()
 
@@ -361,14 +361,14 @@ func (ng *Engine) exec(ctx context.Context, q *query) (Value, error) {
 
 	// The base context might already be canceled on the first iteration (e.g. during shutdown).
 	if err := contextDone(ctx, env); err != nil {
-		return nil, err
+		return nil, err, nil
 	}
 
 	switch s := q.Statement().(type) {
 	case *EvalStmt:
 		return ng.execEvalStmt(ctx, q, s)
 	case testStmt:
-		return nil, s(ctx)
+		return nil, s(ctx), nil
 	}
 
 	panic(fmt.Errorf("promql.Engine.exec: unhandled statement of type %T", q.Statement()))
@@ -383,9 +383,9 @@ func durationMilliseconds(d time.Duration) int64 {
 }
 
 // execEvalStmt evaluates the expression of an evaluation statement for the given time range.
-func (ng *Engine) execEvalStmt(ctx context.Context, query *query, s *EvalStmt) (Value, error) {
+func (ng *Engine) execEvalStmt(ctx context.Context, query *query, s *EvalStmt) (Value, error, storage.Warnings) {
 	prepareSpanTimer, ctxPrepare := query.stats.GetSpanTimer(ctx, stats.QueryPreparationTime, ng.metrics.queryPrepareTime)
-	querier, err := ng.populateSeries(ctxPrepare, query.queryable, s)
+	querier, err, warnings := ng.populateSeries(ctxPrepare, query.queryable, s)
 	prepareSpanTimer.Finish()
 
 	// XXX(fabxc): the querier returned by populateSeries might be instantiated
@@ -396,7 +396,7 @@ func (ng *Engine) execEvalStmt(ctx context.Context, query *query, s *EvalStmt) (
 	}
 
 	if err != nil {
-		return nil, err
+		return nil, err, warnings
 	}
 
 	evalSpanTimer, _ := query.stats.GetSpanTimer(ctx, stats.InnerEvalTime, ng.metrics.queryInnerEval)
@@ -413,7 +413,7 @@ func (ng *Engine) execEvalStmt(ctx context.Context, query *query, s *EvalStmt) (
 		}
 		val, err := evaluator.Eval(s.Expr)
 		if err != nil {
-			return nil, err
+			return nil, err, warnings
 		}
 
 		evalSpanTimer.Finish()
@@ -432,11 +432,11 @@ func (ng *Engine) execEvalStmt(ctx context.Context, query *query, s *EvalStmt) (
 				// timestamp as that is when we ran the evaluation.
 				vector[i] = Sample{Metric: s.Metric, Point: Point{V: s.Points[0].V, T: start}}
 			}
-			return vector, nil
+			return vector, nil, warnings
 		case ValueTypeScalar:
-			return Scalar{V: mat[0].Points[0].V, T: start}, nil
+			return Scalar{V: mat[0].Points[0].V, T: start}, nil, warnings
 		case ValueTypeMatrix:
-			return mat, nil
+			return mat, nil, warnings
 		default:
 			panic(fmt.Errorf("promql.Engine.exec: unexpected expression type %q", s.Expr.Type()))
 		}
@@ -454,7 +454,7 @@ func (ng *Engine) execEvalStmt(ctx context.Context, query *query, s *EvalStmt) (
 	}
 	val, err := evaluator.Eval(s.Expr)
 	if err != nil {
-		return nil, err
+		return nil, err, warnings
 	}
 	evalSpanTimer.Finish()
 
@@ -465,7 +465,7 @@ func (ng *Engine) execEvalStmt(ctx context.Context, query *query, s *EvalStmt) (
 	query.matrix = mat
 
 	if err := contextDone(ctx, "expression evaluation"); err != nil {
-		return nil, err
+		return nil, err, warnings
 	}
 
 	// TODO(fabxc): order ensured by storage?
@@ -474,10 +474,10 @@ func (ng *Engine) execEvalStmt(ctx context.Context, query *query, s *EvalStmt) (
 	sort.Sort(mat)
 	sortSpanTimer.Finish()
 
-	return mat, nil
+	return mat, nil, warnings
 }
 
-func (ng *Engine) populateSeries(ctx context.Context, q storage.Queryable, s *EvalStmt) (storage.Querier, error) {
+func (ng *Engine) populateSeries(ctx context.Context, q storage.Queryable, s *EvalStmt) (storage.Querier, error, storage.Warnings) {
 	var maxOffset time.Duration
 	Inspect(s.Expr, func(node Node, _ []Node) error {
 		switch n := node.(type) {
@@ -503,11 +503,14 @@ func (ng *Engine) populateSeries(ctx context.Context, q storage.Queryable, s *Ev
 
 	querier, err := q.Querier(ctx, timestamp.FromTime(mint), timestamp.FromTime(s.End))
 	if err != nil {
-		return nil, err
+		return nil, err, nil
 	}
 
+	var warnings storage.Warnings
+
 	Inspect(s.Expr, func(node Node, path []Node) error {
 		var set storage.SeriesSet
+		var wrn storage.Warnings
 		params := &storage.SelectParams{
 			Start: timestamp.FromTime(s.Start),
 			End:   timestamp.FromTime(s.End),
@@ -524,17 +527,13 @@ func (ng *Engine) populateSeries(ctx context.Context, q storage.Queryable, s *Ev
 				params.End = params.End - offsetMilliseconds
 			}
 
-			set, err = querier.Select(params, n.LabelMatchers...)
+			set, err, wrn = querier.Select(params, n.LabelMatchers...)
+			warnings = append(warnings, wrn...)
 			if err != nil {
 				level.Error(ng.logger).Log("msg", "error selecting series set", "err", err)
 				return err
 			}
-			n.series, err = expandSeriesSet(ctx, set)
-			if err != nil {
-				// TODO(fabxc): use multi-error.
-				level.Error(ng.logger).Log("msg", "error expanding series set", "err", err)
-				return err
-			}
+			n.unexpandedSeriesSet = set
 
 		case *MatrixSelector:
 			params.Func = extractFuncFromPath(path)
@@ -547,20 +546,17 @@ func (ng *Engine) populateSeries(ctx context.Context, q storage.Queryable, s *Ev
 				params.End = params.End - offsetMilliseconds
 			}
 
-			set, err = querier.Select(params, n.LabelMatchers...)
+			set, err, wrn = querier.Select(params, n.LabelMatchers...)
+			warnings = append(warnings, wrn...)
 			if err != nil {
 				level.Error(ng.logger).Log("msg", "error selecting series set", "err", err)
 				return err
 			}
-			n.series, err = expandSeriesSet(ctx, set)
-			if err != nil {
-				level.Error(ng.logger).Log("msg", "error expanding series set", "err", err)
-				return err
-			}
+			n.unexpandedSeriesSet = set
 		}
 		return nil
 	})
-	return querier, err
+	return querier, err, warnings
 }
 
 // extractFuncFromPath walks up the path and searches for the first instance of
@@ -582,6 +578,30 @@ func extractFuncFromPath(p []Node) string {
 	return extractFuncFromPath(p[:len(p)-1])
 }
 
+func checkForSeriesSetExpansion(expr Expr, ctx context.Context) error {
+	switch e := expr.(type) {
+	case *MatrixSelector:
+		if e.series == nil {
+			series, err := expandSeriesSet(ctx, e.unexpandedSeriesSet)
+			if err != nil {
+				panic(err)
+			} else {
+				e.series = series
+			}
+		}
+	case *VectorSelector:
+		if e.series == nil {
+			series, err := expandSeriesSet(ctx, e.unexpandedSeriesSet)
+			if err != nil {
+				panic(err)
+			} else {
+				e.series = series
+			}
+		}
+	}
+	return nil
+}
+
 func expandSeriesSet(ctx context.Context, it storage.SeriesSet) (res []storage.Series, err error) {
 	for it.Next() {
 		select {
@@ -887,6 +907,9 @@ func (ev *evaluator) eval(expr Expr) Value {
 		}
 
 		sel := e.Args[matrixArgIndex].(*MatrixSelector)
+		if err := checkForSeriesSetExpansion(sel, ev.ctx); err != nil {
+			ev.error(err)
+		}
 		mat := make(Matrix, 0, len(sel.series)) // Output matrix.
 		offset := durationMilliseconds(sel.Offset)
 		selRange := durationMilliseconds(sel.Range)
@@ -1018,6 +1041,9 @@ func (ev *evaluator) eval(expr Expr) Value {
 		})
 
 	case *VectorSelector:
+		if err := checkForSeriesSetExpansion(e, ev.ctx); err != nil {
+			ev.error(err)
+		}
 		mat := make(Matrix, 0, len(e.series))
 		it := storage.NewBuffer(durationMilliseconds(LookbackDelta))
 		for i, s := range e.series {
@@ -1058,6 +1084,10 @@ func (ev *evaluator) eval(expr Expr) Value {
 
 // vectorSelector evaluates a *VectorSelector expression.
 func (ev *evaluator) vectorSelector(node *VectorSelector, ts int64) Vector {
+	if err := checkForSeriesSetExpansion(node, ev.ctx); err != nil {
+		ev.error(err)
+	}
+
 	var (
 		vec = make(Vector, 0, len(node.series))
 	)
@@ -1127,17 +1157,20 @@ func putPointSlice(p []Point) {
 
 // matrixSelector evaluates a *MatrixSelector expression.
 func (ev *evaluator) matrixSelector(node *MatrixSelector) Matrix {
+	if err := checkForSeriesSetExpansion(node, ev.ctx); err != nil {
+		ev.error(err)
+	}
+
 	var (
 		offset = durationMilliseconds(node.Offset)
 		maxt   = ev.startTimestamp - offset
 		mint   = maxt - durationMilliseconds(node.Range)
 		matrix = make(Matrix, 0, len(node.series))
-		err    error
 	)
 
 	it := storage.NewBuffer(durationMilliseconds(node.Range))
 	for i, s := range node.series {
-		if err = contextDone(ev.ctx, "expression evaluation"); err != nil {
+		if err := contextDone(ev.ctx, "expression evaluation"); err != nil {
 			ev.error(err)
 		}
 		it.Reset(s.Iterator())

promql/engine_test.go

@@ -169,8 +169,8 @@ type errQuerier struct {
 	err error
 }
 
-func (q *errQuerier) Select(*storage.SelectParams, ...*labels.Matcher) (storage.SeriesSet, error) {
-	return errSeriesSet{err: q.err}, q.err
+func (q *errQuerier) Select(*storage.SelectParams, ...*labels.Matcher) (storage.SeriesSet, error, storage.Warnings) {
+	return errSeriesSet{err: q.err}, q.err, nil
 }
 func (*errQuerier) LabelValues(name string) ([]string, error) { return nil, nil }
 func (*errQuerier) LabelNames() ([]string, error)             { return nil, nil }
@@ -425,7 +425,8 @@ load 10s
 			MaxSamples: 1,
 			Result: Result{
 				nil,
-				Scalar{V: 1, T: 1000}},
+				Scalar{V: 1, T: 1000},
+				nil},
 			Start: time.Unix(1, 0),
 		},
 		{
@@ -434,6 +435,7 @@ load 10s
 			Result: Result{
 				ErrTooManySamples(env),
 				nil,
+				nil,
 			},
 			Start: time.Unix(1, 0),
 		},
@@ -443,6 +445,7 @@ load 10s
 			Result: Result{
 				ErrTooManySamples(env),
 				nil,
+				nil,
 			},
 			Start: time.Unix(1, 0),
 		},
@@ -455,6 +458,7 @@ load 10s
 					Sample{Point: Point{V: 1, T: 1000},
 						Metric: labels.FromStrings("__name__", "metric")},
 				},
+				nil,
 			},
 			Start: time.Unix(1, 0),
 		},
@@ -467,6 +471,7 @@ load 10s
 					Points: []Point{{V: 1, T: 0}, {V: 2, T: 10000}},
 					Metric: labels.FromStrings("__name__", "metric")},
 				},
+				nil,
 			},
 			Start: time.Unix(10, 0),
 		},
@@ -476,6 +481,7 @@ load 10s
 			Result: Result{
 				ErrTooManySamples(env),
 				nil,
+				nil,
 			},
 			Start: time.Unix(10, 0),
 		},
@@ -489,6 +495,7 @@ load 10s
 					Points: []Point{{V: 1, T: 0}, {V: 1, T: 1000}, {V: 1, T: 2000}},
 					Metric: labels.FromStrings()},
 				},
+				nil,
 			},
 			Start:    time.Unix(0, 0),
 			End:      time.Unix(2, 0),
@@ -500,6 +507,7 @@ load 10s
 			Result: Result{
 				ErrTooManySamples(env),
 				nil,
+				nil,
 			},
 			Start:    time.Unix(0, 0),
 			End:      time.Unix(2, 0),
@@ -514,6 +522,7 @@ load 10s
 					Points: []Point{{V: 1, T: 0}, {V: 1, T: 1000}, {V: 1, T: 2000}},
 					Metric: labels.FromStrings("__name__", "metric")},
 				},
+				nil,
 			},
 			Start:    time.Unix(0, 0),
 			End:      time.Unix(2, 0),
@@ -525,6 +534,7 @@ load 10s
 			Result: Result{
 				ErrTooManySamples(env),
 				nil,
+				nil,
 			},
 			Start:    time.Unix(0, 0),
 			End:      time.Unix(2, 0),
@@ -539,6 +549,7 @@ load 10s
 					Points: []Point{{V: 1, T: 0}, {V: 1, T: 5000}, {V: 2, T: 10000}},
 					Metric: labels.FromStrings("__name__", "metric")},
 				},
+				nil,
 			},
 			Start:    time.Unix(0, 0),
 			End:      time.Unix(10, 0),
@@ -550,6 +561,7 @@ load 10s
 			Result: Result{
 				ErrTooManySamples(env),
 				nil,
+				nil,
 			},
 			Start:    time.Unix(0, 0),
 			End:      time.Unix(10, 0),

promql/value.go

@@ -20,6 +20,7 @@ import (
 	"strings"
 
 	"github.com/prometheus/prometheus/pkg/labels"
+	"github.com/prometheus/prometheus/storage"
 )
 
 // Value is a generic interface for values resulting from a query evaluation.
@@ -201,8 +202,9 @@ func (m Matrix) ContainsSameLabelset() bool {
 // Result holds the resulting value of an execution or an error
 // if any occurred.
 type Result struct {
-	Err   error
-	Value Value
+	Err      error
+	Value    Value
+	Warnings storage.Warnings
 }
 
 // Vector returns a Vector if the result value is one. An error is returned if

rules/manager.go

@@ -490,6 +490,7 @@ func (g *Group) RestoreForState(ts time.Time) {
 		level.Error(g.logger).Log("msg", "Failed to get Querier", "err", err)
 		return
 	}
+	defer q.Close()
 
 	for _, rule := range g.Rules() {
 		alertRule, ok := rule.(*AlertingRule)
@@ -517,7 +518,7 @@ func (g *Group) RestoreForState(ts time.Time) {
 				matchers = append(matchers, mt)
 			}
 
-			sset, err := q.Select(nil, matchers...)
+			sset, err, _ := q.Select(nil, matchers...)
 			if err != nil {
 				level.Error(g.logger).Log("msg", "Failed to restore 'for' state",
 					labels.AlertName, alertRule.Name(), "stage", "Select", "err", err)

rules/manager_test.go

@@ -538,7 +538,7 @@ func TestStaleness(t *testing.T) {
 	matcher, err := labels.NewMatcher(labels.MatchEqual, model.MetricNameLabel, "a_plus_one")
 	testutil.Ok(t, err)
 
-	set, err := querier.Select(nil, matcher)
+	set, err, _ := querier.Select(nil, matcher)
 	testutil.Ok(t, err)
 
 	samples, err := readSeriesSet(set)

storage/fanout.go

@@ -68,23 +68,23 @@ func (f *fanout) Querier(ctx context.Context, mint, maxt int64) (Querier, error)
 	queriers := make([]Querier, 0, 1+len(f.secondaries))
 
 	// Add primary querier
-	querier, err := f.primary.Querier(ctx, mint, maxt)
+	primaryQuerier, err := f.primary.Querier(ctx, mint, maxt)
 	if err != nil {
 		return nil, err
 	}
-	queriers = append(queriers, querier)
+	queriers = append(queriers, primaryQuerier)
 
 	// Add secondary queriers
 	for _, storage := range f.secondaries {
 		querier, err := storage.Querier(ctx, mint, maxt)
 		if err != nil {
-			NewMergeQuerier(queriers).Close()
+			NewMergeQuerier(primaryQuerier, queriers).Close()
 			return nil, err
 		}
 		queriers = append(queriers, querier)
 	}
 
-	return NewMergeQuerier(queriers), nil
+	return NewMergeQuerier(primaryQuerier, queriers), nil
 }
 
 func (f *fanout) Appender() (Appender, error) {
@@ -190,14 +190,18 @@ func (f *fanoutAppender) Rollback() (err error) {
 
 // mergeQuerier implements Querier.
 type mergeQuerier struct {
-	queriers []Querier
+	primaryQuerier Querier
+	queriers       []Querier
+
+	failedQueriers map[Querier]struct{}
+	setQuerierMap  map[SeriesSet]Querier
 }
 
 // NewMergeQuerier returns a new Querier that merges results of input queriers.
 // NB NewMergeQuerier will return NoopQuerier if no queriers are passed to it,
 // and will filter NoopQueriers from its arguments, in order to reduce overhead
 // when only one querier is passed.
-func NewMergeQuerier(queriers []Querier) Querier {
+func NewMergeQuerier(primaryQuerier Querier, queriers []Querier) Querier {
 	filtered := make([]Querier, 0, len(queriers))
 	for _, querier := range queriers {
 		if querier != NoopQuerier() {
@@ -205,6 +209,9 @@ func NewMergeQuerier(queriers []Querier) Querier {
 		}
 	}
 
+	setQuerierMap := make(map[SeriesSet]Querier)
+	failedQueriers := make(map[Querier]struct{})
+
 	switch len(filtered) {
 	case 0:
 		return NoopQuerier()
@@ -212,22 +219,37 @@ func NewMergeQuerier(queriers []Querier) Querier {
 		return filtered[0]
 	default:
 		return &mergeQuerier{
-			queriers: filtered,
+			primaryQuerier: primaryQuerier,
+			queriers:       filtered,
+			failedQueriers: failedQueriers,
+			setQuerierMap:  setQuerierMap,
 		}
 	}
 }
 
 // Select returns a set of series that matches the given label matchers.
-func (q *mergeQuerier) Select(params *SelectParams, matchers ...*labels.Matcher) (SeriesSet, error) {
+func (q *mergeQuerier) Select(params *SelectParams, matchers ...*labels.Matcher) (SeriesSet, error, Warnings) {
 	seriesSets := make([]SeriesSet, 0, len(q.queriers))
+	var warnings Warnings
 	for _, querier := range q.queriers {
-		set, err := querier.Select(params, matchers...)
+		set, err, wrn := querier.Select(params, matchers...)
+		q.setQuerierMap[set] = querier
+		if wrn != nil {
+			warnings = append(warnings, wrn...)
+		}
 		if err != nil {
-			return nil, err
+			q.failedQueriers[querier] = struct{}{}
+			// If the error source isn't the primary querier, return the error as a warning and continue.
+			if querier != q.primaryQuerier {
+				warnings = append(warnings, err)
+				continue
+			} else {
+				return nil, err, nil
+			}
 		}
 		seriesSets = append(seriesSets, set)
 	}
-	return NewMergeSeriesSet(seriesSets), nil
+	return NewMergeSeriesSet(seriesSets, q), nil, warnings
 }
 
 // LabelValues returns all potential values for a label name.
@@ -243,6 +265,11 @@ func (q *mergeQuerier) LabelValues(name string) ([]string, error) {
 	return mergeStringSlices(results), nil
 }
 
+func (q *mergeQuerier) IsFailedSet(set SeriesSet) bool {
+	_, isFailedQuerier := q.failedQueriers[q.setQuerierMap[set]]
+	return isFailedQuerier
+}
+
 func mergeStringSlices(ss [][]string) []string {
 	switch len(ss) {
 	case 0:
@@ -322,11 +349,13 @@ type mergeSeriesSet struct {
 	currentSets   []SeriesSet
 	heap          seriesSetHeap
 	sets          []SeriesSet
+
+	querier *mergeQuerier
 }
 
 // NewMergeSeriesSet returns a new series set that merges (deduplicates)
 // series returned by the input series sets when iterating.
-func NewMergeSeriesSet(sets []SeriesSet) SeriesSet {
+func NewMergeSeriesSet(sets []SeriesSet, querier *mergeQuerier) SeriesSet {
 	if len(sets) == 1 {
 		return sets[0]
 	}
@@ -335,34 +364,53 @@ func NewMergeSeriesSet(sets []SeriesSet) SeriesSet {
 	// series under the cursor.
 	var h seriesSetHeap
 	for _, set := range sets {
+		if set == nil {
+			continue
+		}
 		if set.Next() {
 			heap.Push(&h, set)
 		}
 	}
 	return &mergeSeriesSet{
-		heap: h,
-		sets: sets,
+		heap:    h,
+		sets:    sets,
+		querier: querier,
 	}
 }
 
 func (c *mergeSeriesSet) Next() bool {
-	// Firstly advance all the current series sets.  If any of them have run out
-	// we can drop them, otherwise they should be inserted back into the heap.
-	for _, set := range c.currentSets {
-		if set.Next() {
-			heap.Push(&c.heap, set)
+	// Run in a loop because the "next" series sets may not be valid anymore.
+	// If a remote querier fails, we discard all series sets from that querier.
+	// If, for the current label set, all the next series sets come from
+	// failed remote storage sources, we want to keep trying with the next label set.
+	for {
+		// Firstly advance all the current series sets.  If any of them have run out
+		// we can drop them, otherwise they should be inserted back into the heap.
+		for _, set := range c.currentSets {
+			if set.Next() {
+				heap.Push(&c.heap, set)
+			}
+		}
+		if len(c.heap) == 0 {
+			return false
 		}
-	}
-	if len(c.heap) == 0 {
-		return false
-	}
 
-	// Now, pop items of the heap that have equal label sets.
-	c.currentSets = nil
-	c.currentLabels = c.heap[0].At().Labels()
-	for len(c.heap) > 0 && labels.Equal(c.currentLabels, c.heap[0].At().Labels()) {
-		set := heap.Pop(&c.heap).(SeriesSet)
-		c.currentSets = append(c.currentSets, set)
+		// Now, pop items of the heap that have equal label sets.
+		c.currentSets = nil
+		c.currentLabels = c.heap[0].At().Labels()
+		for len(c.heap) > 0 && labels.Equal(c.currentLabels, c.heap[0].At().Labels()) {
+			set := heap.Pop(&c.heap).(SeriesSet)
+			if c.querier != nil && c.querier.IsFailedSet(set) {
+				continue
+			}
+			c.currentSets = append(c.currentSets, set)
+		}
+
+		// As long as the current set contains at least 1 set,
+		// then it should return true.
+		if len(c.currentSets) != 0 {
+			break
+		}
 	}
 	return true
 }

storage/fanout_test.go

@@ -109,7 +109,7 @@ func TestMergeSeriesSet(t *testing.T) {
 			),
 		},
 	} {
-		merged := NewMergeSeriesSet(tc.input)
+		merged := NewMergeSeriesSet(tc.input, nil)
 		for merged.Next() {
 			require.True(t, tc.expected.Next())
 			actualSeries := merged.At()
@@ -262,7 +262,7 @@ func makeMergeSeriesSet(numSeriesSets, numSeries, numSamples int) SeriesSet {
 	for i := 0; i < numSeriesSets; i++ {
 		seriesSets = append(seriesSets, makeSeriesSet(numSeries, numSamples))
 	}
-	return NewMergeSeriesSet(seriesSets)
+	return NewMergeSeriesSet(seriesSets, nil)
 }
 
 func benchmarkDrain(seriesSet SeriesSet, b *testing.B) {

storage/interface.go

@@ -52,7 +52,7 @@ type Queryable interface {
 // Querier provides reading access to time series data.
 type Querier interface {
 	// Select returns a set of series that matches the given label matchers.
-	Select(*SelectParams, ...*labels.Matcher) (SeriesSet, error)
+	Select(*SelectParams, ...*labels.Matcher) (SeriesSet, error, Warnings)
 
 	// LabelValues returns all potential values for a label name.
 	LabelValues(name string) ([]string, error)
@@ -122,3 +122,5 @@ type SeriesIterator interface {
 	// Err returns the current error.
 	Err() error
 }
+
+type Warnings []error

storage/noop.go

@@ -26,8 +26,8 @@ func NoopQuerier() Querier {
 	return noopQuerier{}
 }
 
-func (noopQuerier) Select(*SelectParams, ...*labels.Matcher) (SeriesSet, error) {
-	return NoopSeriesSet(), nil
+func (noopQuerier) Select(*SelectParams, ...*labels.Matcher) (SeriesSet, error, Warnings) {
+	return NoopSeriesSet(), nil, nil
 }
 
 func (noopQuerier) LabelValues(name string) ([]string, error) {

storage/remote/read.go

@@ -59,10 +59,10 @@ type querier struct {
 
 // Select implements storage.Querier and uses the given matchers to read series
 // sets from the Client.
-func (q *querier) Select(p *storage.SelectParams, matchers ...*labels.Matcher) (storage.SeriesSet, error) {
+func (q *querier) Select(p *storage.SelectParams, matchers ...*labels.Matcher) (storage.SeriesSet, error, storage.Warnings) {
 	query, err := ToQuery(q.mint, q.maxt, matchers, p)
 	if err != nil {
-		return nil, err
+		return nil, err, nil
 	}
 
 	remoteReadGauge := remoteReadQueries.WithLabelValues(q.client.Name())
@@ -71,10 +71,10 @@ func (q *querier) Select(p *storage.SelectParams, matchers ...*labels.Matcher) (
 
 	res, err := q.client.Read(q.ctx, query)
 	if err != nil {
-		return nil, err
+		return nil, err, nil
 	}
 
-	return FromQueryResult(res), nil
+	return FromQueryResult(res), nil, nil
 }
 
 // LabelValues implements storage.Querier and is a noop.
@@ -117,13 +117,13 @@ type externalLabelsQuerier struct {
 // Select adds equality matchers for all external labels to the list of matchers
 // before calling the wrapped storage.Queryable. The added external labels are
 // removed from the returned series sets.
-func (q externalLabelsQuerier) Select(p *storage.SelectParams, matchers ...*labels.Matcher) (storage.SeriesSet, error) {
+func (q externalLabelsQuerier) Select(p *storage.SelectParams, matchers ...*labels.Matcher) (storage.SeriesSet, error, storage.Warnings) {
 	m, added := q.addExternalLabels(matchers)
-	s, err := q.Querier.Select(p, m...)
+	s, err, warnings := q.Querier.Select(p, m...)
 	if err != nil {
-		return nil, err
+		return nil, err, warnings
 	}
-	return newSeriesSetFilter(s, added), nil
+	return newSeriesSetFilter(s, added), nil, warnings
 }
 
 // PreferLocalStorageFilter returns a QueryableFunc which creates a NoopQuerier
@@ -170,7 +170,7 @@ type requiredMatchersQuerier struct {
 
 // Select returns a NoopSeriesSet if the given matchers don't match the label
 // set of the requiredMatchersQuerier. Otherwise it'll call the wrapped querier.
-func (q requiredMatchersQuerier) Select(p *storage.SelectParams, matchers ...*labels.Matcher) (storage.SeriesSet, error) {
+func (q requiredMatchersQuerier) Select(p *storage.SelectParams, matchers ...*labels.Matcher) (storage.SeriesSet, error, storage.Warnings) {
 	ms := q.requiredMatchers
 	for _, m := range matchers {
 		for i, r := range ms {
@@ -184,7 +184,7 @@ func (q requiredMatchersQuerier) Select(p *storage.SelectParams, matchers ...*la
 		}
 	}
 	if len(ms) > 0 {
-		return storage.NoopSeriesSet(), nil
+		return storage.NoopSeriesSet(), nil, nil
 	}
 	return q.Querier.Select(p, matchers...)
 }
@@ -225,6 +225,15 @@ func newSeriesSetFilter(ss storage.SeriesSet, toFilter model.LabelSet) storage.S
 type seriesSetFilter struct {
 	storage.SeriesSet
 	toFilter model.LabelSet
+	querier  storage.Querier
+}
+
+func (ssf *seriesSetFilter) GetQuerier() storage.Querier {
+	return ssf.querier
+}
+
+func (ssf *seriesSetFilter) SetQuerier(querier storage.Querier) {
+	ssf.querier = querier
 }
 
 func (ssf seriesSetFilter) At() storage.Series {

storage/remote/read_test.go

@@ -42,7 +42,7 @@ func TestExternalLabelsQuerierSelect(t *testing.T) {
 		externalLabels: model.LabelSet{"region": "europe"},
 	}
 	want := newSeriesSetFilter(mockSeriesSet{}, q.externalLabels)
-	have, err := q.Select(nil, matchers...)
+	have, err, _ := q.Select(nil, matchers...)
 	if err != nil {
 		t.Error(err)
 	}
@@ -157,8 +157,8 @@ type mockSeriesSet struct {
 	storage.SeriesSet
 }
 
-func (mockQuerier) Select(*storage.SelectParams, ...*labels.Matcher) (storage.SeriesSet, error) {
-	return mockSeriesSet{}, nil
+func (mockQuerier) Select(*storage.SelectParams, ...*labels.Matcher) (storage.SeriesSet, error, storage.Warnings) {
+	return mockSeriesSet{}, nil, nil
 }
 
 func TestPreferLocalStorageFilter(t *testing.T) {
@@ -313,7 +313,7 @@ func TestRequiredLabelsQuerierSelect(t *testing.T) {
 			requiredMatchers: test.requiredMatchers,
 		}
 
-		have, err := q.Select(nil, test.matchers...)
+		have, err, _ := q.Select(nil, test.matchers...)
 		if err != nil {
 			t.Error(err)
 		}

storage/remote/storage.go

@@ -140,7 +140,7 @@ func (s *Storage) Querier(ctx context.Context, mint, maxt int64) (storage.Querie
 		}
 		queriers = append(queriers, q)
 	}
-	return storage.NewMergeQuerier(queriers), nil
+	return storage.NewMergeQuerier(nil, queriers), nil
 }
 
 // Close the background processing of the storage queues.

storage/tsdb/tsdb.go

@@ -230,7 +230,7 @@ type querier struct {
 	q tsdb.Querier
 }
 
-func (q querier) Select(_ *storage.SelectParams, oms ...*labels.Matcher) (storage.SeriesSet, error) {
+func (q querier) Select(_ *storage.SelectParams, oms ...*labels.Matcher) (storage.SeriesSet, error, storage.Warnings) {
 	ms := make([]tsdbLabels.Matcher, 0, len(oms))
 
 	for _, om := range oms {
@@ -238,9 +238,9 @@ func (q querier) Select(_ *storage.SelectParams, oms ...*labels.Matcher) (storag
 	}
 	set, err := q.q.Select(ms...)
 	if err != nil {
-		return nil, err
+		return nil, err, nil
 	}
-	return seriesSet{set: set}, nil
+	return seriesSet{set: set}, nil, nil
 }
 
 func (q querier) LabelValues(name string) ([]string, error) { return q.q.LabelValues(name) }

web/api/v1/api.go

@@ -119,6 +119,14 @@ type response struct {
 	Data      interface{} `json:"data,omitempty"`
 	ErrorType errorType   `json:"errorType,omitempty"`
 	Error     string      `json:"error,omitempty"`
+	Warnings  []string    `json:"warnings,omitempty"`
+}
+
+type apiFuncResult struct {
+	data      interface{}
+	err       *apiError
+	warnings  storage.Warnings
+	finalizer func()
 }
 
 // Enables cross-site script calls.
@@ -128,7 +136,7 @@ func setCORS(w http.ResponseWriter) {
 	}
 }
 
-type apiFunc func(r *http.Request) (interface{}, *apiError, func())
+type apiFunc func(r *http.Request) apiFuncResult
 
 // TSDBAdmin defines the tsdb interfaces used by the v1 API for admin operations.
 type TSDBAdmin interface {
@@ -204,16 +212,16 @@ func (api *API) Register(r *route.Router) {
 	wrap := func(f apiFunc) http.HandlerFunc {
 		hf := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			setCORS(w)
-			data, err, finalizer := f(r)
-			if err != nil {
-				api.respondError(w, err, data)
-			} else if data != nil {
-				api.respond(w, data)
+			result := f(r)
+			if result.err != nil {
+				api.respondError(w, result.err, result.data)
+			} else if result.data != nil {
+				api.respond(w, result.data, result.warnings)
 			} else {
 				w.WriteHeader(http.StatusNoContent)
 			}
-			if finalizer != nil {
-				finalizer()
+			if result.finalizer != nil {
+				result.finalizer()
 			}
 		})
 		return api.ready(httputil.CompressionHandler{
@@ -258,17 +266,17 @@ type queryData struct {
 	Stats      *stats.QueryStats `json:"stats,omitempty"`
 }
 
-func (api *API) options(r *http.Request) (interface{}, *apiError, func()) {
-	return nil, nil, nil
+func (api *API) options(r *http.Request) apiFuncResult {
+	return apiFuncResult{nil, nil, nil, nil}
 }
 
-func (api *API) query(r *http.Request) (interface{}, *apiError, func()) {
+func (api *API) query(r *http.Request) apiFuncResult {
 	var ts time.Time
 	if t := r.FormValue("time"); t != "" {
 		var err error
 		ts, err = parseTime(t)
 		if err != nil {
-			return nil, &apiError{errorBadData, err}, nil
+			return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 		}
 	} else {
 		ts = api.now()
@@ -279,7 +287,7 @@ func (api *API) query(r *http.Request) (interface{}, *apiError, func()) {
 		var cancel context.CancelFunc
 		timeout, err := parseDuration(to)
 		if err != nil {
-			return nil, &apiError{errorBadData, err}, nil
+			return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 		}
 
 		ctx, cancel = context.WithTimeout(ctx, timeout)
@@ -288,12 +296,12 @@ func (api *API) query(r *http.Request) (interface{}, *apiError, func()) {
 
 	qry, err := api.QueryEngine.NewInstantQuery(api.Queryable, r.FormValue("query"), ts)
 	if err != nil {
-		return nil, &apiError{errorBadData, err}, nil
+		return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 	}
 
 	res := qry.Exec(ctx)
 	if res.Err != nil {
-		return nil, returnAPIError(res.Err), qry.Close
+		return apiFuncResult{nil, returnAPIError(res.Err), res.Warnings, qry.Close}
 	}
 
 	// Optional stats field in response if parameter "stats" is not empty.
@@ -302,42 +310,42 @@ func (api *API) query(r *http.Request) (interface{}, *apiError, func()) {
 		qs = stats.NewQueryStats(qry.Stats())
 	}
 
-	return &queryData{
+	return apiFuncResult{&queryData{
 		ResultType: res.Value.Type(),
 		Result:     res.Value,
 		Stats:      qs,
-	}, nil, qry.Close
+	}, nil, res.Warnings, qry.Close}
 }
 
-func (api *API) queryRange(r *http.Request) (interface{}, *apiError, func()) {
+func (api *API) queryRange(r *http.Request) apiFuncResult {
 	start, err := parseTime(r.FormValue("start"))
 	if err != nil {
-		return nil, &apiError{errorBadData, err}, nil
+		return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 	}
 	end, err := parseTime(r.FormValue("end"))
 	if err != nil {
-		return nil, &apiError{errorBadData, err}, nil
+		return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 	}
 	if end.Before(start) {
 		err := errors.New("end timestamp must not be before start time")
-		return nil, &apiError{errorBadData, err}, nil
+		return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 	}
 
 	step, err := parseDuration(r.FormValue("step"))
 	if err != nil {
-		return nil, &apiError{errorBadData, err}, nil
+		return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 	}
 
 	if step <= 0 {
 		err := errors.New("zero or negative query resolution step widths are not accepted. Try a positive integer")
-		return nil, &apiError{errorBadData, err}, nil
+		return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 	}
 
 	// For safety, limit the number of returned points per timeseries.
 	// This is sufficient for 60s resolution for a week or 1h resolution for a year.
 	if end.Sub(start)/step > 11000 {
 		err := errors.New("exceeded maximum resolution of 11,000 points per timeseries. Try decreasing the query resolution (?step=XX)")
-		return nil, &apiError{errorBadData, err}, nil
+		return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 	}
 
 	ctx := r.Context()
@@ -345,7 +353,7 @@ func (api *API) queryRange(r *http.Request) (interface{}, *apiError, func()) {
 		var cancel context.CancelFunc
 		timeout, err := parseDuration(to)
 		if err != nil {
-			return nil, &apiError{errorBadData, err}, nil
+			return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 		}
 
 		ctx, cancel = context.WithTimeout(ctx, timeout)
@@ -354,12 +362,12 @@ func (api *API) queryRange(r *http.Request) (interface{}, *apiError, func()) {
 
 	qry, err := api.QueryEngine.NewRangeQuery(api.Queryable, r.FormValue("query"), start, end, step)
 	if err != nil {
-		return nil, &apiError{errorBadData, err}, nil
+		return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 	}
 
 	res := qry.Exec(ctx)
 	if res.Err != nil {
-		return nil, returnAPIError(res.Err), qry.Close
+		return apiFuncResult{nil, returnAPIError(res.Err), res.Warnings, qry.Close}
 	}
 
 	// Optional stats field in response if parameter "stats" is not empty.
@@ -368,11 +376,11 @@ func (api *API) queryRange(r *http.Request) (interface{}, *apiError, func()) {
 		qs = stats.NewQueryStats(qry.Stats())
 	}
 
-	return &queryData{
+	return apiFuncResult{&queryData{
 		ResultType: res.Value.Type(),
 		Result:     res.Value,
 		Stats:      qs,
-	}, nil, qry.Close
+	}, nil, res.Warnings, qry.Close}
 }
 
 func returnAPIError(err error) *apiError {
@@ -392,39 +400,39 @@ func returnAPIError(err error) *apiError {
 	return &apiError{errorExec, err}
 }
 
-func (api *API) labelNames(r *http.Request) (interface{}, *apiError, func()) {
+func (api *API) labelNames(r *http.Request) apiFuncResult {
 	q, err := api.Queryable.Querier(r.Context(), math.MinInt64, math.MaxInt64)
 	if err != nil {
-		return nil, &apiError{errorExec, err}, nil
+		return apiFuncResult{nil, &apiError{errorExec, err}, nil, nil}
 	}
 	defer q.Close()
 
 	names, err := q.LabelNames()
 	if err != nil {
-		return nil, &apiError{errorExec, err}, nil
+		return apiFuncResult{nil, &apiError{errorExec, err}, nil, nil}
 	}
-	return names, nil, nil
+	return apiFuncResult{names, nil, nil, nil}
 }
 
-func (api *API) labelValues(r *http.Request) (interface{}, *apiError, func()) {
+func (api *API) labelValues(r *http.Request) apiFuncResult {
 	ctx := r.Context()
 	name := route.Param(ctx, "name")
 
 	if !model.LabelNameRE.MatchString(name) {
-		return nil, &apiError{errorBadData, fmt.Errorf("invalid label name: %q", name)}, nil
+		return apiFuncResult{nil, &apiError{errorBadData, fmt.Errorf("invalid label name: %q", name)}, nil, nil}
 	}
 	q, err := api.Queryable.Querier(ctx, math.MinInt64, math.MaxInt64)
 	if err != nil {
-		return nil, &apiError{errorExec, err}, nil
+		return apiFuncResult{nil, &apiError{errorExec, err}, nil, nil}
 	}
 	defer q.Close()
 
 	vals, err := q.LabelValues(name)
 	if err != nil {
-		return nil, &apiError{errorExec, err}, nil
+		return apiFuncResult{nil, &apiError{errorExec, err}, nil, nil}
 	}
 
-	return vals, nil, nil
+	return apiFuncResult{vals, nil, nil, nil}
 }
 
 var (
@@ -432,12 +440,12 @@ var (
 	maxTime = time.Unix(math.MaxInt64/1000-62135596801, 999999999)
 )
 
-func (api *API) series(r *http.Request) (interface{}, *apiError, func()) {
+func (api *API) series(r *http.Request) apiFuncResult {
 	if err := r.ParseForm(); err != nil {
-		return nil, &apiError{errorBadData, fmt.Errorf("error parsing form values: %v", err)}, nil
+		return apiFuncResult{nil, &apiError{errorBadData, fmt.Errorf("error parsing form values: %v", err)}, nil, nil}
 	}
 	if len(r.Form["match[]"]) == 0 {
-		return nil, &apiError{errorBadData, fmt.Errorf("no match[] parameter provided")}, nil
+		return apiFuncResult{nil, &apiError{errorBadData, fmt.Errorf("no match[] parameter provided")}, nil, nil}
 	}
 
 	var start time.Time
@@ -445,7 +453,7 @@ func (api *API) series(r *http.Request) (interface{}, *apiError, func()) {
 		var err error
 		start, err = parseTime(t)
 		if err != nil {
-			return nil, &apiError{errorBadData, err}, nil
+			return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 		}
 	} else {
 		start = minTime
@@ -456,7 +464,7 @@ func (api *API) series(r *http.Request) (interface{}, *apiError, func()) {
 		var err error
 		end, err = parseTime(t)
 		if err != nil {
-			return nil, &apiError{errorBadData, err}, nil
+			return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 		}
 	} else {
 		end = maxTime
@@ -466,40 +474,42 @@ func (api *API) series(r *http.Request) (interface{}, *apiError, func()) {
 	for _, s := range r.Form["match[]"] {
 		matchers, err := promql.ParseMetricSelector(s)
 		if err != nil {
-			return nil, &apiError{errorBadData, err}, nil
+			return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 		}
 		matcherSets = append(matcherSets, matchers)
 	}
 
 	q, err := api.Queryable.Querier(r.Context(), timestamp.FromTime(start), timestamp.FromTime(end))
 	if err != nil {
-		return nil, &apiError{errorExec, err}, nil
+		return apiFuncResult{nil, &apiError{errorExec, err}, nil, nil}
 	}
 	defer q.Close()
 
 	var sets []storage.SeriesSet
+	var warnings storage.Warnings
 	for _, mset := range matcherSets {
-		s, err := q.Select(nil, mset...)
+		s, err, wrn := q.Select(nil, mset...) //TODO
+		warnings = append(warnings, wrn...)
 		if err != nil {
-			return nil, &apiError{errorExec, err}, nil
+			return apiFuncResult{nil, &apiError{errorExec, err}, warnings, nil}
 		}
 		sets = append(sets, s)
 	}
 
-	set := storage.NewMergeSeriesSet(sets)
+	set := storage.NewMergeSeriesSet(sets, nil)
 	metrics := []labels.Labels{}
 	for set.Next() {
 		metrics = append(metrics, set.At().Labels())
 	}
 	if set.Err() != nil {
-		return nil, &apiError{errorExec, set.Err()}, nil
+		return apiFuncResult{nil, &apiError{errorExec, set.Err()}, warnings, nil}
 	}
 
-	return metrics, nil, nil
+	return apiFuncResult{metrics, nil, warnings, nil}
 }
 
-func (api *API) dropSeries(r *http.Request) (interface{}, *apiError, func()) {
-	return nil, &apiError{errorInternal, fmt.Errorf("not implemented")}, nil
+func (api *API) dropSeries(r *http.Request) apiFuncResult {
+	return apiFuncResult{nil, &apiError{errorInternal, fmt.Errorf("not implemented")}, nil, nil}
 }
 
 // Target has the information for one target.
@@ -528,7 +538,7 @@ type TargetDiscovery struct {
 	DroppedTargets []*DroppedTarget `json:"droppedTargets"`
 }
 
-func (api *API) targets(r *http.Request) (interface{}, *apiError, func()) {
+func (api *API) targets(r *http.Request) apiFuncResult {
 	flatten := func(targets map[string][]*scrape.Target) []*scrape.Target {
 		var n int
 		keys := make([]string, 0, len(targets))
@@ -570,7 +580,7 @@ func (api *API) targets(r *http.Request) (interface{}, *apiError, func()) {
 			DiscoveredLabels: t.DiscoveredLabels().Map(),
 		})
 	}
-	return res, nil, nil
+	return apiFuncResult{res, nil, nil, nil}
 }
 
 func matchLabels(lset labels.Labels, matchers []*labels.Matcher) bool {
@@ -582,18 +592,18 @@ func matchLabels(lset labels.Labels, matchers []*labels.Matcher) bool {
 	return true
 }
 
-func (api *API) targetMetadata(r *http.Request) (interface{}, *apiError, func()) {
+func (api *API) targetMetadata(r *http.Request) apiFuncResult {
 	limit := -1
 	if s := r.FormValue("limit"); s != "" {
 		var err error
 		if limit, err = strconv.Atoi(s); err != nil {
-			return nil, &apiError{errorBadData, fmt.Errorf("limit must be a number")}, nil
+			return apiFuncResult{nil, &apiError{errorBadData, fmt.Errorf("limit must be a number")}, nil, nil}
 		}
 	}
 
 	matchers, err := promql.ParseMetricSelector(r.FormValue("match_target"))
 	if err != nil {
-		return nil, &apiError{errorBadData, err}, nil
+		return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 	}
 
 	metric := r.FormValue("metric")
@@ -633,9 +643,9 @@ func (api *API) targetMetadata(r *http.Request) (interface{}, *apiError, func())
 		}
 	}
 	if len(res) == 0 {
-		return nil, &apiError{errorNotFound, errors.New("specified metadata not found")}, nil
+		return apiFuncResult{nil, &apiError{errorNotFound, errors.New("specified metadata not found")}, nil, nil}
 	}
-	return res, nil, nil
+	return apiFuncResult{res, nil, nil, nil}
 }
 
 type metricMetadata struct {
@@ -657,7 +667,7 @@ type AlertmanagerTarget struct {
 	URL string `json:"url"`
 }
 
-func (api *API) alertmanagers(r *http.Request) (interface{}, *apiError, func()) {
+func (api *API) alertmanagers(r *http.Request) apiFuncResult {
 	urls := api.alertmanagerRetriever.Alertmanagers()
 	droppedURLS := api.alertmanagerRetriever.DroppedAlertmanagers()
 	ams := &AlertmanagerDiscovery{ActiveAlertmanagers: make([]*AlertmanagerTarget, len(urls)), DroppedAlertmanagers: make([]*AlertmanagerTarget, len(droppedURLS))}
@@ -667,7 +677,7 @@ func (api *API) alertmanagers(r *http.Request) (interface{}, *apiError, func())
 	for i, url := range droppedURLS {
 		ams.DroppedAlertmanagers[i] = &AlertmanagerTarget{URL: url.String()}
 	}
-	return ams, nil, nil
+	return apiFuncResult{ams, nil, nil, nil}
 }
 
 // AlertDiscovery has info for all active alerts.
@@ -684,7 +694,7 @@ type Alert struct {
 	Value       float64       `json:"value"`
 }
 
-func (api *API) alerts(r *http.Request) (interface{}, *apiError, func()) {
+func (api *API) alerts(r *http.Request) apiFuncResult {
 	alertingRules := api.rulesRetriever.AlertingRules()
 	alerts := []*Alert{}
 
@@ -697,7 +707,7 @@ func (api *API) alerts(r *http.Request) (interface{}, *apiError, func()) {
 
 	res := &AlertDiscovery{Alerts: alerts}
 
-	return res, nil, nil
+	return apiFuncResult{res, nil, nil, nil}
 }
 
 func rulesAlertsToAPIAlerts(rulesAlerts []*rules.Alert) []*Alert {
@@ -756,7 +766,7 @@ type recordingRule struct {
 	Type string `json:"type"`
 }
 
-func (api *API) rules(r *http.Request) (interface{}, *apiError, func()) {
+func (api *API) rules(r *http.Request) apiFuncResult {
 	ruleGroups := api.rulesRetriever.RuleGroups()
 	res := &RuleDiscovery{RuleGroups: make([]*RuleGroup, len(ruleGroups))}
 	for i, grp := range ruleGroups {
@@ -799,29 +809,29 @@ func (api *API) rules(r *http.Request) (interface{}, *apiError, func()) {
 				}
 			default:
 				err := fmt.Errorf("failed to assert type of rule '%v'", rule.Name())
-				return nil, &apiError{errorInternal, err}, nil
+				return apiFuncResult{nil, &apiError{errorInternal, err}, nil, nil}
 			}
 
 			apiRuleGroup.Rules = append(apiRuleGroup.Rules, enrichedRule)
 		}
 		res.RuleGroups[i] = apiRuleGroup
 	}
-	return res, nil, nil
+	return apiFuncResult{res, nil, nil, nil}
 }
 
 type prometheusConfig struct {
 	YAML string `json:"yaml"`
 }
 
-func (api *API) serveConfig(r *http.Request) (interface{}, *apiError, func()) {
+func (api *API) serveConfig(r *http.Request) apiFuncResult {
 	cfg := &prometheusConfig{
 		YAML: api.config().String(),
 	}
-	return cfg, nil, nil
+	return apiFuncResult{cfg, nil, nil, nil}
 }
 
-func (api *API) serveFlags(r *http.Request) (interface{}, *apiError, func()) {
-	return api.flagsMap, nil, nil
+func (api *API) serveFlags(r *http.Request) apiFuncResult {
+	return apiFuncResult{api.flagsMap, nil, nil, nil}
 }
 
 func (api *API) remoteRead(w http.ResponseWriter, r *http.Request) {
@@ -873,7 +883,7 @@ func (api *API) remoteRead(w http.ResponseWriter, r *http.Request) {
 			}
 		}
 
-		set, err := querier.Select(selectParams, filteredMatchers...)
+		set, err, _ := querier.Select(selectParams, filteredMatchers...)
 		if err != nil {
 			http.Error(w, err.Error(), http.StatusInternalServerError)
 			return
@@ -911,20 +921,20 @@ func (api *API) remoteRead(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
-func (api *API) deleteSeries(r *http.Request) (interface{}, *apiError, func()) {
+func (api *API) deleteSeries(r *http.Request) apiFuncResult {
 	if !api.enableAdmin {
-		return nil, &apiError{errorUnavailable, errors.New("Admin APIs disabled")}, nil
+		return apiFuncResult{nil, &apiError{errorUnavailable, errors.New("Admin APIs disabled")}, nil, nil}
 	}
 	db := api.db()
 	if db == nil {
-		return nil, &apiError{errorUnavailable, errors.New("TSDB not ready")}, nil
+		return apiFuncResult{nil, &apiError{errorUnavailable, errors.New("TSDB not ready")}, nil, nil}
 	}
 
 	if err := r.ParseForm(); err != nil {
-		return nil, &apiError{errorBadData, fmt.Errorf("error parsing form values: %v", err)}, nil
+		return apiFuncResult{nil, &apiError{errorBadData, fmt.Errorf("error parsing form values: %v", err)}, nil, nil}
 	}
 	if len(r.Form["match[]"]) == 0 {
-		return nil, &apiError{errorBadData, fmt.Errorf("no match[] parameter provided")}, nil
+		return apiFuncResult{nil, &apiError{errorBadData, fmt.Errorf("no match[] parameter provided")}, nil, nil}
 	}
 
 	var start time.Time
@@ -932,7 +942,7 @@ func (api *API) deleteSeries(r *http.Request) (interface{}, *apiError, func()) {
 		var err error
 		start, err = parseTime(t)
 		if err != nil {
-			return nil, &apiError{errorBadData, err}, nil
+			return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 		}
 	} else {
 		start = minTime
@@ -943,7 +953,7 @@ func (api *API) deleteSeries(r *http.Request) (interface{}, *apiError, func()) {
 		var err error
 		end, err = parseTime(t)
 		if err != nil {
-			return nil, &apiError{errorBadData, err}, nil
+			return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 		}
 	} else {
 		end = maxTime
@@ -952,7 +962,7 @@ func (api *API) deleteSeries(r *http.Request) (interface{}, *apiError, func()) {
 	for _, s := range r.Form["match[]"] {
 		matchers, err := promql.ParseMetricSelector(s)
 		if err != nil {
-			return nil, &apiError{errorBadData, err}, nil
+			return apiFuncResult{nil, &apiError{errorBadData, err}, nil, nil}
 		}
 
 		var selector tsdbLabels.Selector
@@ -961,16 +971,16 @@ func (api *API) deleteSeries(r *http.Request) (interface{}, *apiError, func()) {
 		}
 
 		if err := db.Delete(timestamp.FromTime(start), timestamp.FromTime(end), selector...); err != nil {
-			return nil, &apiError{errorInternal, err}, nil
+			return apiFuncResult{nil, &apiError{errorInternal, err}, nil, nil}
 		}
 	}
 
-	return nil, nil, nil
+	return apiFuncResult{nil, nil, nil, nil}
 }
 
-func (api *API) snapshot(r *http.Request) (interface{}, *apiError, func()) {
+func (api *API) snapshot(r *http.Request) apiFuncResult {
 	if !api.enableAdmin {
-		return nil, &apiError{errorUnavailable, errors.New("Admin APIs disabled")}, nil
+		return apiFuncResult{nil, &apiError{errorUnavailable, errors.New("Admin APIs disabled")}, nil, nil}
 	}
 	var (
 		skipHead bool
@@ -979,13 +989,13 @@ func (api *API) snapshot(r *http.Request) (interface{}, *apiError, func()) {
 	if r.FormValue("skip_head") != "" {
 		skipHead, err = strconv.ParseBool(r.FormValue("skip_head"))
 		if err != nil {
-			return nil, &apiError{errorBadData, fmt.Errorf("unable to parse boolean 'skip_head' argument: %v", err)}, nil
+			return apiFuncResult{nil, &apiError{errorBadData, fmt.Errorf("unable to parse boolean 'skip_head' argument: %v", err)}, nil, nil}
 		}
 	}
 
 	db := api.db()
 	if db == nil {
-		return nil, &apiError{errorUnavailable, errors.New("TSDB not ready")}, nil
+		return apiFuncResult{nil, &apiError{errorUnavailable, errors.New("TSDB not ready")}, nil, nil}
 	}
 
 	var (
@@ -996,31 +1006,31 @@ func (api *API) snapshot(r *http.Request) (interface{}, *apiError, func()) {
 		dir = filepath.Join(snapdir, name)
 	)
 	if err := os.MkdirAll(dir, 0777); err != nil {
-		return nil, &apiError{errorInternal, fmt.Errorf("create snapshot directory: %s", err)}, nil
+		return apiFuncResult{nil, &apiError{errorInternal, fmt.Errorf("create snapshot directory: %s", err)}, nil, nil}
 	}
 	if err := db.Snapshot(dir, !skipHead); err != nil {
-		return nil, &apiError{errorInternal, fmt.Errorf("create snapshot: %s", err)}, nil
+		return apiFuncResult{nil, &apiError{errorInternal, fmt.Errorf("create snapshot: %s", err)}, nil, nil}
 	}
 
-	return struct {
+	return apiFuncResult{struct {
 		Name string `json:"name"`
-	}{name}, nil, nil
+	}{name}, nil, nil, nil}
 }
 
-func (api *API) cleanTombstones(r *http.Request) (interface{}, *apiError, func()) {
+func (api *API) cleanTombstones(r *http.Request) apiFuncResult {
 	if !api.enableAdmin {
-		return nil, &apiError{errorUnavailable, errors.New("Admin APIs disabled")}, nil
+		return apiFuncResult{nil, &apiError{errorUnavailable, errors.New("Admin APIs disabled")}, nil, nil}
 	}
 	db := api.db()
 	if db == nil {
-		return nil, &apiError{errorUnavailable, errors.New("TSDB not ready")}, nil
+		return apiFuncResult{nil, &apiError{errorUnavailable, errors.New("TSDB not ready")}, nil, nil}
 	}
 
 	if err := db.CleanTombstones(); err != nil {
-		return nil, &apiError{errorInternal, err}, nil
+		return apiFuncResult{nil, &apiError{errorInternal, err}, nil, nil}
 	}
 
-	return nil, nil, nil
+	return apiFuncResult{nil, nil, nil, nil}
 }
 
 func convertMatcher(m *labels.Matcher) tsdbLabels.Matcher {
@@ -1075,11 +1085,17 @@ func mergeLabels(primary, secondary []*prompb.Label) []*prompb.Label {
 	return result
 }
 
-func (api *API) respond(w http.ResponseWriter, data interface{}) {
+func (api *API) respond(w http.ResponseWriter, data interface{}, warnings storage.Warnings) {
+	statusMessage := statusSuccess
+	var warningStrings []string
+	for _, warning := range warnings {
+		warningStrings = append(warningStrings, warning.Error())
+	}
 	json := jsoniter.ConfigCompatibleWithStandardLibrary
 	b, err := json.Marshal(&response{
-		Status: statusSuccess,
-		Data:   data,
+		Status:   statusMessage,
+		Data:     data,
+		Warnings: warningStrings,
 	})
 	if err != nil {
 		level.Error(api.logger).Log("msg", "error marshaling json response", "err", err)
@@ -1134,6 +1150,7 @@ func (api *API) respondError(w http.ResponseWriter, apiErr *apiError, data inter
 func parseTime(s string) (time.Time, error) {
 	if t, err := strconv.ParseFloat(s, 64); err == nil {
 		s, ns := math.Modf(t)
+		ns = math.Round(ns*1000) / 1000
 		return time.Unix(int64(s), int64(ns*float64(time.Second))), nil
 	}
 	if t, err := time.Parse(time.RFC3339Nano, s); err == nil {

web/api/v1/api_test.go

@@ -349,9 +349,9 @@ func TestLabelNames(t *testing.T) {
 		ctx := context.Background()
 		req, err := request(method)
 		testutil.Ok(t, err)
-		resp, apiErr, _ := api.labelNames(req.WithContext(ctx))
-		assertAPIError(t, apiErr, "")
-		assertAPIResponse(t, resp, []string{"__name__", "baz", "foo", "foo1", "foo2", "xyz"})
+		res := api.labelNames(req.WithContext(ctx))
+		assertAPIError(t, res.err, "")
+		assertAPIResponse(t, res.data, []string{"__name__", "baz", "foo", "foo1", "foo2", "xyz"})
 	}
 }
 
@@ -379,7 +379,7 @@ func setupRemote(s storage.Storage) *httptest.Server {
 			}
 			defer querier.Close()
 
-			set, err := querier.Select(selectParams, matchers...)
+			set, err, _ := querier.Select(selectParams, matchers...)
 			if err != nil {
 				http.Error(w, err.Error(), http.StatusInternalServerError)
 				return
@@ -857,9 +857,9 @@ func testEndpoints(t *testing.T, api *API, testLabelAPI bool) {
 			if err != nil {
 				t.Fatal(err)
 			}
-			resp, apiErr, _ := test.endpoint(req.WithContext(ctx))
-			assertAPIError(t, apiErr, test.errType)
-			assertAPIResponse(t, resp, test.response)
+			res := test.endpoint(req.WithContext(ctx))
+			assertAPIError(t, res.err, test.errType)
+			assertAPIResponse(t, res.data, test.response)
 		}
 	}
 }
@@ -1202,8 +1202,8 @@ func TestAdminEndpoints(t *testing.T) {
 			if err != nil {
 				t.Fatalf("Error when creating test request: %s", err)
 			}
-			_, apiErr, _ := endpoint(req)
-			assertAPIError(t, apiErr, tc.errType)
+			res := endpoint(req)
+			assertAPIError(t, res.err, tc.errType)
 		})
 	}
 }
@@ -1211,7 +1211,7 @@ func TestAdminEndpoints(t *testing.T) {
 func TestRespondSuccess(t *testing.T) {
 	s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		api := API{}
-		api.respond(w, "test")
+		api.respond(w, "test", nil)
 	}))
 	defer s.Close()
 
@@ -1318,6 +1318,10 @@ func TestParseTime(t *testing.T) {
 		}, {
 			input:  "2015-06-03T14:21:58.555+01:00",
 			result: ts,
+		}, {
+			// Test float rounding.
+			input:  "1543578564.705",
+			result: time.Unix(1543578564, 705*1e6),
 		},
 	}
 
@@ -1502,7 +1506,7 @@ func TestRespond(t *testing.T) {
 	for _, c := range cases {
 		s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			api := API{}
-			api.respond(w, c.response)
+			api.respond(w, c.response, nil)
 		}))
 		defer s.Close()
 
@@ -1543,6 +1547,6 @@ func BenchmarkRespond(b *testing.B) {
 	b.ResetTimer()
 	api := API{}
 	for n := 0; n < b.N; n++ {
-		api.respond(&testResponseWriter, response)
+		api.respond(&testResponseWriter, response, nil)
 	}
 }

web/federate.go

@@ -37,6 +37,10 @@ var (
 		Name: "prometheus_web_federation_errors_total",
 		Help: "Total number of errors that occurred while sending federation responses.",
 	})
+	federationWarnings = prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "prometheus_web_federation_warnings_total",
+		Help: "Total number of warnings that occurred while sending federation responses.",
+	})
 )
 
 func (h *Handler) federation(w http.ResponseWriter, req *http.Request) {
@@ -83,7 +87,11 @@ func (h *Handler) federation(w http.ResponseWriter, req *http.Request) {
 
 	var sets []storage.SeriesSet
 	for _, mset := range matcherSets {
-		s, err := q.Select(params, mset...)
+		s, err, wrns := q.Select(params, mset...)
+		if wrns != nil {
+			level.Debug(h.logger).Log("msg", "federation select returned warnings", "warnings", wrns)
+			federationErrors.Add(float64(len(wrns)))
+		}
 		if err != nil {
 			federationErrors.Inc()
 			http.Error(w, err.Error(), http.StatusInternalServerError)
@@ -92,7 +100,7 @@ func (h *Handler) federation(w http.ResponseWriter, req *http.Request) {
 		sets = append(sets, s)
 	}
 
-	set := storage.NewMergeSeriesSet(sets)
+	set := storage.NewMergeSeriesSet(sets, nil)
 	it := storage.NewBuffer(int64(promql.LookbackDelta / 1e6))
 	for set.Next() {
 		s := set.At()

web/web.go

@@ -55,7 +55,6 @@ import (
 
 	"github.com/prometheus/prometheus/config"
 	"github.com/prometheus/prometheus/notifier"
-	"github.com/prometheus/prometheus/pkg/labels"
 	"github.com/prometheus/prometheus/promql"
 	"github.com/prometheus/prometheus/rules"
 	"github.com/prometheus/prometheus/scrape"
@@ -191,6 +190,12 @@ type Options struct {
 	RemoteReadConcurrencyLimit int
 }
 
+func instrumentHandlerWithPrefix(prefix string) func(handlerName string, handler http.HandlerFunc) http.HandlerFunc {
+	return func(handlerName string, handler http.HandlerFunc) http.HandlerFunc {
+		return instrumentHandler(prefix+handlerName, handler)
+	}
+}
+
 func instrumentHandler(handlerName string, handler http.HandlerFunc) http.HandlerFunc {
 	return promhttp.InstrumentHandlerDuration(
 		requestDuration.MustCurryWith(prometheus.Labels{"handler": handlerName}),
@@ -459,7 +464,7 @@ func (h *Handler) Run(ctx context.Context) error {
 	mux := http.NewServeMux()
 	mux.Handle("/", h.router)
 
-	av1 := route.New().WithInstrumentation(instrumentHandler)
+	av1 := route.New().WithInstrumentation(instrumentHandlerWithPrefix("/api/v1"))
 	h.apiV1.Register(av1)
 	apiPath := "/api"
 	if h.options.RoutePrefix != "/" {
@@ -703,7 +708,8 @@ func (h *Handler) targets(w http.ResponseWriter, r *http.Request) {
 	tps := h.scrapeManager.TargetsActive()
 	for _, targets := range tps {
 		sort.Slice(targets, func(i, j int) bool {
-			return targets[i].Labels().Get(labels.InstanceName) < targets[j].Labels().Get(labels.InstanceName)
+			return targets[i].Labels().Get(model.JobLabel) < targets[j].Labels().Get(model.JobLabel) ||
+				targets[i].Labels().Get(model.InstanceLabel) < targets[j].Labels().Get(model.InstanceLabel)
 		})
 	}