Create PromQL-based alerting policies (API)

This page describes how to create a PromQL-based alerting policy by using the Cloud Monitoring API. You can use PromQL queries in your alerting policies to create complex conditions with features such as ratios, dynamic thresholds, and metric evaluation.

For general information, see PromQL-based alerting overview.

If you work in a Prometheus environment outside Cloud Monitoring and have Prometheus alerting rules, then you can use the Google Cloud CLI to migrate them to PromQL-based alerting policies in Monitoring. For more information, see Migrate alerting rules and receivers from Prometheus.

Create alerting policies with PromQL queries

You use the alertPolicies.create method to programmatically create alerting policies.

The only difference between creating PromQL-based alerting policies and other alerting policies is that your Condition type must be PrometheusQueryLanguageCondition. This condition type allows alerting policies to be defined with PromQL.

The following shows a PromQL query for an alerting policy condition that uses a metric from the kube-state exporter to find the number of times that a container has been restarted in the last 30 minutes:

rate(kube_pod_container_status_restarts[30m]) * 1800 > 1

Constructing the alerting policy

To build a PromQL-based alerting policy, use the AlertPolicy condition type PrometheusQueryLanguageCondition. The PrometheusQueryLanguageCondition has the following structure:

{
  "query": string,
  "duration": string,
  "evaluationInterval": string,
  "labels": {string: string},
  "ruleGroup": string,
  "alertRule": string
}

The PrometheusQueryLanguageCondition fields have the following definitions:

query: The PromQL expression to evaluate. Equivalent to the expr field from a standard Prometheus alerting rule.
duration: Specifies the length of time during which each evaluation of the query must generate a true value before the condition of the alerting policy is met. The value must be a number of minutes, expressed in seconds; for example, 600s for a 10-minute duration. For more information, see Behavior of metric-based alerting policies.
evaluationInterval: The interval of time, in seconds, between PromQL evaluations of the query. The default value is 30 seconds. If the PrometheusQueryLanguageCondition was created by migrating a Prometheus alerting rule, then this value comes from the Prometheus rule group that contained the Prometheus alerting rule.

Note: Incidents created by a PromQL-based alerting policy don't follow the alerting policy autoclose duration. Instead, the incident is automatically closed when it reaches a set time after the last time the condition was met. This time is the larger of 270 seconds and twice the condition's evaluation interval.
labels: An optional way to add or overwrite labels in the PromQL expression result.
ruleGroup: If the alerting policy was migrated from a Prometheus configuration file, then this field contains the value of the name field from the rule group in the Prometheus configuration file. This field isn't required when you make a PromQL alerting policy in Cloud Monitoring API.
alertRule: If the alerting policy was migrated from a Prometheus configuration file, then this field contains the value of the alert field from the alerting rule in the Prometheus configuration file. This field isn't required when you make a PromQL alerting policy in Cloud Monitoring API.

For example, the following condition uses a PromQL query to find the number of times that a container has been restarted in the last 30 minutes:

"conditionPrometheusQueryLanguage": {
  "query": "rate(kube_pod_container_status_restarts[30m]) * 1800 > 1",
  "duration": "600s",
  evaluationInterval: "60s",
  "alertRule": "ContainerRestartCount",
  "labels": {
    "action_required":"true",
    "severity":"critical/warning/info"}
}

Use this structure as the value of a conditionPrometheusQueryLanguage field in a condition, which is in turn embedded in an alerting-policy structure. For more information about these structures, see AlertPolicy.

The following shows a complete policy with a PrometheusQueryLanguageCondition condition in JSON:

{
  "displayName": "Container Restarts",
  "documentation": {
    "content": "Pod ${resource.label.namespace_name}/${resource.label.pod_name} has restarted more than once during the last 30 minutes.",
    "mimeType": "text/markdown",
    "subject": "Container ${resource.label.container_name} in Pod ${resource.label.namespace_name}/${resource.label.pod_name} has restarted more than once during the last 30 minutes."
  },
  "userLabels": {},
  "conditions": [
    {
      "displayName": "Container has restarted",
      "conditionPrometheusQueryLanguage": {
        "query": "rate(kubernetes_io:container_restart_count[30m]) * 1800",
        "duration": "600s",
        evaluationInterval: "60s",
        "alertRule": "ContainerRestart",
        "labels": {
          "action_required":"true",
          "severity":"critical/warning/info"}
      }
    }
  ],
  "combiner": "OR",
  "enabled": true
}

Create an alerting policy

To create the alerting policy, put the alerting policy JSON into a file called POLICY_NAME.json, and then run the following command:

curl -d @POLICY_NAME.json -H "Authorization: Bearer $TOKEN"
-H 'Content-Type: application/json'
-X POST https://monitoring.googleapis.com/v3/projects/${PROJECT}/alertPolicies

For more information about the Monitoring API for alerting policies, see Managing alerting policies by API.

For more information about using curl, see Invoking curl.

Disable check for metric existence

When you create a PromQL-based alerting policy, Google Cloud runs a validation to ensure that the metrics referenced in the condition already exist in Monitoring. However, you can override this validation if you need to create an alerting policy before the metrics exist. For example, you might want to do so when using automation to create new projects that come with a standard set of predefined alerting policies. If you don't disable the validation, then your alerting policy creation fails until the underlying metrics are created.

To disable the check for metric existence, add the field "disableMetricValidation": true to your PrometheusQueryLanguageCondition:

{
  "query": string,
  "duration": string,
  "evaluationInterval": string,
  "labels": {string: string},
  "ruleGroup": string,
  "disableMetricValidation": true,
  "alertRule": string
}

If the condition of an alerting policy references a metric that doesn't exist, then the condition still runs according to its evaluation interval. However, the query result is always empty. After the underlying metric exists, the query returns data.

Use Terraform

For instructions on configuring PromQL-based alerting policies using Terraform, see the condition_prometheus_query_language section of the google_monitoring_alert_policy Terraform registry.

For general information about using Google Cloud with Terraform, see Terraform with Google Cloud.

Invoking `curl`

Each curl invocation includes a set of arguments, followed by the URL of an API resource. The common arguments include a Google Cloud project ID and an authentication token. These values are represented here by the PROJECT_ID and TOKEN environment variables.

You might also have to specify other arguments, for example, to specify the type of the HTTP request (for example, -X DELETE). The default request is GET, so the examples don't specify it.

Each curl invocation has this general structure:

curl --http1.1 --header "Authorization: Bearer ${TOKEN}" <other_args> https://monitoring.googleapis.com/v3/projects/${PROJECT_ID}/<request>

To use curl, you must specify your project ID and an access token. To reduce typing and errors, you can put these into environment variables as pass them to curl that way.

To set these variables, do the following:

Create an environment variable to hold the ID of your scoping project of a metrics scope. These steps call the variable PROJECT_ID:
```
PROJECT_ID=a-sample-project
```
Authenticate to the Google Cloud CLI:
```
gcloud auth login
```
Optional. To avoid having to specify your project ID with each gcloud command, set your project ID as the default by using gcloud CLI:
```
gcloud config set project ${PROJECT_ID}
```
Create an authorization token and capture it in an environment variable. These steps call the variable TOKEN:
```
TOKEN=`gcloud auth print-access-token`
```
You have to periodically refresh the access token. If commands that worked suddenly report that you are unauthenticated, reissue this command.
To verify that you got an access token, echo the TOKEN variable:
```
echo ${TOKEN}
ya29.GluiBj8o....
```