prometheus/retrieval/discovery/consul.go

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// Copyright 2015 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
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// limitations under the License.
package discovery
import (
"fmt"
"net/http"
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"strconv"
"strings"
"sync"
"time"
consul "github.com/hashicorp/consul/api"
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"github.com/prometheus/common/log"
"github.com/prometheus/common/model"
"github.com/prometheus/prometheus/config"
)
const (
consulWatchTimeout = 30 * time.Second
consulRetryInterval = 15 * time.Second
// consulAddressLabel is the name for the label containing a target's address.
consulAddressLabel = model.MetaLabelPrefix + "consul_address"
// consulNodeLabel is the name for the label containing a target's node name.
consulNodeLabel = model.MetaLabelPrefix + "consul_node"
// consulTagsLabel is the name of the label containing the tags assigned to the target.
consulTagsLabel = model.MetaLabelPrefix + "consul_tags"
// consulServiceLabel is the name of the label containing the service name.
consulServiceLabel = model.MetaLabelPrefix + "consul_service"
// consulServiceAddressLabel is the name of the label containing the (optional) service address.
consulServiceAddressLabel = model.MetaLabelPrefix + "consul_service_address"
// consulServicePortLabel is the name of the label containing the service port.
consulServicePortLabel = model.MetaLabelPrefix + "consul_service_port"
// consulDCLabel is the name of the label containing the datacenter ID.
consulDCLabel = model.MetaLabelPrefix + "consul_dc"
// consulServiceIDLabel is the name of the label containing the service ID.
consulServiceIDLabel = model.MetaLabelPrefix + "consul_service_id"
)
// ConsulDiscovery retrieves target information from a Consul server
// and updates them via watches.
type ConsulDiscovery struct {
client *consul.Client
clientConf *consul.Config
clientDatacenter string
tagSeparator string
scrapedServices map[string]struct{}
mu sync.RWMutex
services map[string]*consulService
}
// consulService contains data belonging to the same service.
type consulService struct {
name string
tgroup *config.TargetGroup
lastIndex uint64
removed bool
running bool
done chan struct{}
}
// NewConsulDiscovery returns a new ConsulDiscovery for the given config.
func NewConsulDiscovery(conf *config.ConsulSDConfig) *ConsulDiscovery {
clientConf := &consul.Config{
Address: conf.Server,
Scheme: conf.Scheme,
Datacenter: conf.Datacenter,
Token: conf.Token,
HttpAuth: &consul.HttpBasicAuth{
Username: conf.Username,
Password: conf.Password,
},
}
client, err := consul.NewClient(clientConf)
if err != nil {
// NewClient always returns a nil error.
panic(fmt.Errorf("discovery.NewConsulDiscovery: %s", err))
}
cd := &ConsulDiscovery{
client: client,
clientConf: clientConf,
tagSeparator: conf.TagSeparator,
scrapedServices: map[string]struct{}{},
services: map[string]*consulService{},
}
// If the datacenter isn't set in the clientConf, let's get it from the local Consul agent
// (Consul default is to use local node's datacenter if one isn't given for a query).
if clientConf.Datacenter == "" {
info, err := client.Agent().Self()
if err != nil {
panic(fmt.Errorf("discovery.NewConsulDiscovery: %s", err))
}
cd.clientDatacenter = info["Config"]["Datacenter"].(string)
} else {
cd.clientDatacenter = clientConf.Datacenter
}
for _, name := range conf.Services {
cd.scrapedServices[name] = struct{}{}
}
return cd
}
// Sources implements the TargetProvider interface.
func (cd *ConsulDiscovery) Sources() []string {
clientConf := *cd.clientConf
clientConf.HttpClient = &http.Client{Timeout: 5 * time.Second}
client, err := consul.NewClient(&clientConf)
if err != nil {
// NewClient always returns a nil error.
panic(fmt.Errorf("discovery.ConsulDiscovery.Sources: %s", err))
}
srvs, _, err := client.Catalog().Services(nil)
if err != nil {
log.Errorf("Error refreshing service list: %s", err)
return nil
}
cd.mu.Lock()
defer cd.mu.Unlock()
srcs := make([]string, 0, len(srvs))
for name := range srvs {
if _, ok := cd.scrapedServices[name]; len(cd.scrapedServices) == 0 || ok {
srcs = append(srcs, name)
}
}
return srcs
}
// Run implements the TargetProvider interface.
func (cd *ConsulDiscovery) Run(ch chan<- *config.TargetGroup, done <-chan struct{}) {
defer close(ch)
defer cd.stop()
update := make(chan *consulService, 10)
go cd.watchServices(update, done)
for {
select {
case <-done:
return
case srv := <-update:
if srv.removed {
close(srv.done)
// Send clearing update.
ch <- &config.TargetGroup{Source: srv.name}
break
}
// Launch watcher for the service.
if !srv.running {
go cd.watchService(srv, ch)
srv.running = true
}
}
}
}
func (cd *ConsulDiscovery) stop() {
// The lock prevents Run from terminating while the watchers attempt
// to send on their channels.
cd.mu.Lock()
defer cd.mu.Unlock()
for _, srv := range cd.services {
close(srv.done)
}
}
// watchServices retrieves updates from Consul's services endpoint and sends
// potential updates to the update channel.
func (cd *ConsulDiscovery) watchServices(update chan<- *consulService, done <-chan struct{}) {
var lastIndex uint64
for {
catalog := cd.client.Catalog()
srvs, meta, err := catalog.Services(&consul.QueryOptions{
WaitIndex: lastIndex,
WaitTime: consulWatchTimeout,
})
if err != nil {
log.Errorf("Error refreshing service list: %s", err)
time.Sleep(consulRetryInterval)
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continue
}
// If the index equals the previous one, the watch timed out with no update.
if meta.LastIndex == lastIndex {
continue
}
lastIndex = meta.LastIndex
cd.mu.Lock()
select {
case <-done:
cd.mu.Unlock()
return
default:
// Continue.
}
// Check for new services.
for name := range srvs {
if _, ok := cd.scrapedServices[name]; len(cd.scrapedServices) > 0 && !ok {
continue
}
srv, ok := cd.services[name]
if !ok {
srv = &consulService{
name: name,
tgroup: &config.TargetGroup{},
done: make(chan struct{}),
}
srv.tgroup.Source = name
cd.services[name] = srv
}
srv.tgroup.Labels = model.LabelSet{
consulServiceLabel: model.LabelValue(name),
consulDCLabel: model.LabelValue(cd.clientDatacenter),
}
update <- srv
}
// Check for removed services.
for name, srv := range cd.services {
if _, ok := srvs[name]; !ok {
srv.removed = true
update <- srv
delete(cd.services, name)
}
}
cd.mu.Unlock()
}
}
// watchService retrieves updates about srv from Consul's service endpoint.
// On a potential update the resulting target group is sent to ch.
func (cd *ConsulDiscovery) watchService(srv *consulService, ch chan<- *config.TargetGroup) {
catalog := cd.client.Catalog()
for {
nodes, meta, err := catalog.Service(srv.name, "", &consul.QueryOptions{
WaitIndex: srv.lastIndex,
WaitTime: consulWatchTimeout,
})
if err != nil {
log.Errorf("Error refreshing service %s: %s", srv.name, err)
time.Sleep(consulRetryInterval)
continue
}
// If the index equals the previous one, the watch timed out with no update.
if meta.LastIndex == srv.lastIndex {
continue
}
srv.lastIndex = meta.LastIndex
srv.tgroup.Targets = make([]model.LabelSet, 0, len(nodes))
for _, node := range nodes {
addr := fmt.Sprintf("%s:%d", node.Address, node.ServicePort)
// We surround the separated list with the separator as well. This way regular expressions
// in relabeling rules don't have to consider tag positions.
tags := cd.tagSeparator + strings.Join(node.ServiceTags, cd.tagSeparator) + cd.tagSeparator
srv.tgroup.Targets = append(srv.tgroup.Targets, model.LabelSet{
model.AddressLabel: model.LabelValue(addr),
consulAddressLabel: model.LabelValue(node.Address),
consulNodeLabel: model.LabelValue(node.Node),
consulTagsLabel: model.LabelValue(tags),
consulServiceAddressLabel: model.LabelValue(node.ServiceAddress),
consulServicePortLabel: model.LabelValue(strconv.Itoa(node.ServicePort)),
consulServiceIDLabel: model.LabelValue(node.ServiceID),
})
}
cd.mu.Lock()
select {
case <-srv.done:
cd.mu.Unlock()
return
default:
// Continue.
}
ch <- srv.tgroup
cd.mu.Unlock()
}
}