Prometheus

Prometheus is an open source monitoring system and time series database. You can use Prometheus with Istio to record metrics that track the health of Istio and of applications within the service mesh. You can visualize metrics using tools like Grafana and Kiali.

Configuration

In an Istio mesh, each component exposes an endpoint that emits metrics. Prometheus works by scraping these endpoints and collecting the results. This is configured through the Prometheus configuration file which controls settings for which endpoints to query, the port and path to query, TLS settings, and more.

To gather metrics for the entire mesh, configure Prometheus to scrape:

  1. The control plane (istiod deployment)
  2. Ingress and Egress gateways
  3. The Envoy sidecar
  4. The user applications (if they expose Prometheus metrics)

To simplify the configuration of metrics, Istio offers two modes of operation.

Option 1: Metrics merging

To simplify configuration, Istio has the ability to control scraping entirely by prometheus.io annotations. This allows Istio scraping to work out of the box with standard configurations such as the ones provided by the Helm stable/prometheus charts.

This option is enabled by default but can be disabled by passing --set meshConfig.enablePrometheusMerge=false during installation. When enabled, appropriate prometheus.io annotations will be added to all workloads to set up scraping. If these annotations already exist, they will be overwritten. With this option, the Envoy sidecar will merge Istio’s metrics with the application metrics.

This option exposes all the metrics in plain text.

This feature may not suit your needs in the following situations:

  • You need to scrape metrics using TLS.
  • Your application exposes metrics with the same names as Istio metrics. For example, your application metrics expose an istio_requests_total metric. This might happen if the application is itself running Envoy.
  • Your Prometheus deployment is not configured to scrape based on standard prometheus.io annotations.

If required, this feature can be disabled per workload by adding a prometheus.istio.io/merge-metrics: "false" annotation on a pod.

Option 2: Customized scraping configurations

The built-in demo installation of Prometheus contains all the required scraping configuration. To deploy this instance of Prometheus, follow the steps in Customizable Install with Istioctl to install Istio and pass --set values.prometheus.enabled=true during installation.

This built-in deployment of Prometheus is intended for new users to help them quickly getting started. However, it does not offer advanced customization, like persistence or authentication and as such should not be considered production ready. To use an existing Prometheus instance, add the scraping configurations in prometheus/configmap.yaml to your configuration.

This configuration will add scrape job configurations for the control plane, as well as for all Envoy sidecars. Additionally, a job is configured to scrape application metrics for all pods with relevant prometheus.io annotations:

  • prometheus.io/scrape determines if a pod should be scraped. Set to true to enable scraping.
  • prometheus.io/path determines the path to scrape metrics at. Defaults to /metrics.
  • prometheus.io/port determines the port to scrape metrics at. Defaults to 80.

TLS settings

The control plane, gateway, and Envoy sidecar metrics will all be scraped over plaintext. However, the application metrics will follow whatever Istio configuration has been configured for the workload. In particular, if Strict mTLS is enabled, then Prometheus will need to be configured to scrape using Istio certificates.

When using the bundled Prometheus deployment, this is configured by default. For custom Prometheus deployments, please follow Provision a certificate and key for an application without sidecars to provision a certificate for Prometheus, then add the TLS scraping configuration.

Best practices

For larger meshes, advanced configuration might help Prometheus scale. See Using Prometheus for production-scale monitoring for more information.

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