Add Azure Monitor output plugin

Gopkg.toml

@@ -221,3 +221,7 @@
 [[override]]
   source = "https://github.com/fsnotify/fsnotify/archive/v1.4.7.tar.gz"
   name = "gopkg.in/fsnotify.v1"
+
+[[constraint]]
+  name = "github.com/Azure/go-autorest"
+  version = "10.12.0"

internal/models/running_output.go

@@ -114,6 +114,11 @@ func (ro *RunningOutput) AddMetric(m telegraf.Metric) {
 		m, _ = metric.New(name, tags, fields, t, tp)
 	}
 
+	if output, ok := ro.Output.(telegraf.AggregatingOutput); ok {
+		output.Add(m)
+		return
+	}
+
 	ro.metrics.Add(m)
 	if ro.metrics.Len() == ro.MetricBatchSize {
 		batch := ro.metrics.Batch(ro.MetricBatchSize)
@@ -127,6 +132,12 @@ func (ro *RunningOutput) AddMetric(m telegraf.Metric) {
 
 // Write writes all cached points to this output.
 func (ro *RunningOutput) Write() error {
+	if output, ok := ro.Output.(telegraf.AggregatingOutput); ok {
+		metrics := output.Push()
+		ro.metrics.Add(metrics...)
+		output.Reset()
+	}
+
 	nFails, nMetrics := ro.failMetrics.Len(), ro.metrics.Len()
 	ro.BufferSize.Set(int64(nFails + nMetrics))
 	log.Printf("D! Output [%s] buffer fullness: %d / %d metrics. ",

output.go

@@ -13,6 +13,12 @@ type Output interface {
 	Write(metrics []Metric) error
 }
 
+type AggregatingOutput interface {
+	Add(in Metric)
+	Push() []Metric
+	Reset()
+}
+
 type ServiceOutput interface {
 	// Connect to the Output
 	Connect() error

plugins/outputs/all/all.go

@@ -4,6 +4,7 @@ import (
 	_ "github.com/influxdata/telegraf/plugins/outputs/amon"
 	_ "github.com/influxdata/telegraf/plugins/outputs/amqp"
 	_ "github.com/influxdata/telegraf/plugins/outputs/application_insights"
+	_ "github.com/influxdata/telegraf/plugins/outputs/azure_monitor"
 	_ "github.com/influxdata/telegraf/plugins/outputs/cloudwatch"
 	_ "github.com/influxdata/telegraf/plugins/outputs/cratedb"
 	_ "github.com/influxdata/telegraf/plugins/outputs/datadog"

plugins/outputs/azure_monitor/README.md

@@ -0,0 +1,130 @@
+## Azure Monitor Custom Metrics Output for Telegraf
+
+This plugin will send custom metrics to Azure Monitor. Azure Monitor has a
+metric resolution of one minute. To handle this in Telegraf, the Azure Monitor
+output plugin will automatically aggregates metrics into one minute buckets,
+which are then sent to Azure Monitor on every flush interval.
+
+The metrics from each input plugin will be written to a separate Azure Monitor
+namespace, prefixed with `Telegraf/` by default. The field name for each
+metric is written as the Azure Monitor metric name. All field values are
+written as a summarized set that includes: min, max, sum, count. Tags are
+written as a dimension on each Azure Monitor metric.
+
+Since Azure Monitor only accepts numeric values, string-typed fields are
+dropped by default. There is a configuration option (`strings_as_dimensions`)
+to retain fields that contain strings as extra dimensions. Azure Monitor
+allows a maximum of 10 dimensions per metric so any dimensions over that
+amount will be deterministically dropped.
+
+## Initial Setup
+
+1. [Register your Azure subscription with the `microsoft.insights` resource
+   provider.](https://docs.microsoft.com/en-us/azure/azure-resource-manager/resource-manager-supported-services#portal)
+2. [Consult this chart to identify which regions support Azure Monitor.](https://azure.microsoft.com/en-us/global-infrastructure/services/)
+3. Only some Azure Monitor regions support Custom Metrics. For regions with
+   Custom Metrics support, an endpoint will be available with the format
+   `https://<region>.monitoring.azure.com`. The following regions are
+   currently known to be supported:
+    - West Central US, e.g. `https://westcentralus.monitoring.azure.com`
+    - South Central US, e.g. `https://southcentralus.monitoring.azure.com`
+
+## Azure Authentication
+
+This plugin uses one of several different types of authenticate methods. The
+preferred authentication methods are different from the *order* in which each
+authentication is checked. Here are the preferred authentication methods:
+
+1. Managed Service Identity (MSI) token
+    - This is the prefered authentication method. Telegraf will automatically
+      authenticate using this method when running on Azure VMs.
+2. AAD Application Tokens (Service Principals)
+    - Primarily useful if Telegraf is writing metrics for other resources. [More
+      information](https://docs.microsoft.com/en-us/azure/active-directory/develop/active-directory-application-objects).
+    - A Service Principal or User Principal needs to be assigned the `Monitoring
+      Contributor` roles.
+3. AAD User Tokens (User Principals)
+    - Allows Telegraf to authenticate like a user. It is best to use this method
+      for development.
+
+The plugin will attempt to authenticate with the first available of the
+following configurations in this order:
+
+1. **Client Credentials**: Azure AD Application ID and Secret.
+
+    Set the following Telegraf configuration variables:
+
+    - `azure_tenant_id`: Specifies the Tenant to which to authenticate.
+    - `azure_client_id`: Specifies the app client ID to use.
+    - `azure_client_secret`: Specifies the app secret to use.
+
+    Or set the following environment variables:
+
+    - `AZURE_TENANT_ID`: Specifies the Tenant to which to authenticate.
+    - `AZURE_CLIENT_ID`: Specifies the app client ID to use.
+    - `AZURE_CLIENT_SECRET`: Specifies the app secret to use.
+
+2. **Client Certificate**: Azure AD Application ID and X.509 Certificate.
+
+    - `AZURE_TENANT_ID`: Specifies the Tenant to which to authenticate.
+    - `AZURE_CLIENT_ID`: Specifies the app client ID to use.
+    - `AZURE_CERTIFICATE_PATH`: Specifies the certificate Path to use.
+    - `AZURE_CERTIFICATE_PASSWORD`: Specifies the certificate password to use.
+
+3. **Resource Owner Password**: Azure AD User and Password. This grant type is
+   *not recommended*, use device login instead if you need interactive login.
+
+    - `AZURE_TENANT_ID`: Specifies the Tenant to which to authenticate.
+    - `AZURE_CLIENT_ID`: Specifies the app client ID to use.
+    - `AZURE_USERNAME`: Specifies the username to use.
+    - `AZURE_PASSWORD`: Specifies the password to use.
+
+4. **Azure Managed Service Identity**: Delegate credential management to the
+   platform. Requires that code is running in Azure, e.g. on a VM. All
+   configuration is handled by Azure. See [Azure Managed Service
+   Identity](https://docs.microsoft.com/en-us/azure/active-directory/msi-overview)
+   for more details. Only available on ARM-based resources.
+
+**Note: As shown above, the last option (#4) is the preferred way to
+authenticate when running Telegraf on Azure VMs. Make sure you've followed the
+[initial setup instructions](#initial-setup).**
+
+## Config
+
+The plugin will automatically attempt to discover the region and resource ID
+using the Azure VM Instance Metadata service. If Telegraf is not running on a
+virtual machine or the VM Instance Metadata service is not available, the
+following variables are required for the output to function.
+
+* region
+* resource_id
+
+### Configuration:
+
+```
+[[outputs.azure_monitor]]
+  ## See the [Azure Monitor output plugin README](/plugins/outputs/azure_monitor/README.md)
+  ## for details on authentication options.
+
+  ## Write HTTP timeout, formatted as a string. Defaults to 20s.
+  #timeout = "20s"
+
+  ## Set the namespace prefix, defaults to "Telegraf/<input-name>".
+  #namespace_prefix = "Telegraf/"
+
+  ## Azure Monitor doesn't have a string value type, so convert string
+  ## fields to dimensions (a.k.a. tags) if enabled. Azure Monitor allows
+  ## a maximum of 10 dimensions so Telegraf will only send the first 10
+  ## alphanumeric dimensions.
+  #strings_as_dimensions = false
+
+  ## *The following two fields must be set or be available via the
+  ## Instance Metadata service on Azure Virtual Machines.*
+
+  ## Azure Region to publish metrics against, e.g. eastus, southcentralus.
+  #region = ""
+
+  ## The Azure Resource ID against which metric will be logged, e.g.
+  ## "/subscriptions/<subscription_id>/resourceGroups/<resource_group>/providers/Microsoft.Compute/virtualMachines/<vm_name>"
+  #resource_id = ""
+```