Add Azure tenant and subscription ID labels

Signed-off-by: Fabian Reinartz <freinartz@google.com>

discovery/azure/azure.go

@@ -37,6 +37,8 @@ import (
 
 const (
 	azureLabel                     = model.MetaLabelPrefix + "azure_"
+	azureLabelSubscriptionID       = azureLabel + "subscription_id"
+	azureLabelTenantID             = azureLabel + "tenant_id"
 	azureLabelMachineID            = azureLabel + "machine_id"
 	azureLabelMachineResourceGroup = azureLabel + "machine_resource_group"
 	azureLabelMachineName          = azureLabel + "machine_name"
@@ -332,6 +334,8 @@ func (d *Discovery) refresh() (tg *targetgroup.Group, err error) {
 			}
 
 			labels := model.LabelSet{
+				azureLabelSubscriptionID:       model.LabelValue(d.cfg.SubscriptionID),
+				azureLabelTenantID:             model.LabelValue(d.cfg.TenantID),
 				azureLabelMachineID:            model.LabelValue(vm.ID),
 				azureLabelMachineName:          model.LabelValue(vm.Name),
 				azureLabelMachineOSType:        model.LabelValue(vm.OsType),

docs/configuration/configuration.md

@@ -259,6 +259,8 @@ Azure SD configurations allow retrieving scrape targets from Azure VMs.
 
 The following meta labels are available on targets during relabeling:
 
+* `__meta_azure_subscription_id`: the subscription ID
+* `__meta_azure_tenant_id`: the tenant ID
 * `__meta_azure_machine_id`: the machine ID
 * `__meta_azure_machine_location`: the location the machine runs in
 * `__meta_azure_machine_name`: the machine name