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Integrating Loki Charmed Operator

Overview

This Loki Charmed Operator provides two libraries for integrating with other charms:

The loki_push_api library provides an endpoint URL used to send log entries to Loki from compatible clients. You can read more about this in the official Loki documentation.

The Loki charm supports user-provided alert rules. A client charm (from the 'requiresside of the relation) that needs to forward alert rules to Loki should place them in a directory namedloki_alert_rules within the client charm's source directory (./src`).

A new Loki configuration is generated every time a new relation is created, or an existing one changes.

The library log_proxy provides a way to setup a charms as a Log Proxy (Provider or Consumer) to Loki.

Libraries

loki_push_api

This library provides two main objects:

  • LokiPushApiConsumer: This object may be used by any charmed operator that wants to send logs to Loki by implementing the consumer side of the loki_push_api relation interface. For instance a Promtail, Grafana agent charm, or any other application charm that wants to be able to send logs to Loki.
  • LokiPushApiProvider: This object may be used by any charmed operator that wants to provide a way to push loki logs to it. For instance a Loki charm.

Learn more about this library on charmhub.

log_proxy

This library provides two main objects:

  • LogProxyConsumer: This object may be used by any K8s charmed operator that wants to send logs to Loki through a log proxy by implementing the consumer side of the loki_push_api relation interface. When a relation with a Charmed Operator implementing LogProxyProvider is established, this object injects a Promtail binary into the workload container. This binary will then send logs to Loki through the log proxy provider.

  • LogProxyProvider: This object may be used by any charmed operator that wants to act as a log proxy to Loki by implementing the provider side of the loki_push_api relation interface. For instance, a Grafana agent or Promtail charmed operator receiving logs from a workload and forwarding them to Loki.

Filtering logs in Loki is largely performed on the basis of labels. In the Juju ecosystem, Juju topology labels are used to uniquely identify the workload generating the telemetry (like logs).

In order to be able to control the labels of the logs pushed, this object injects a Pebble layer for running Promtail into the workload container. Promtail will then inject Juju topology labels into each log entry on the fly.

Learn more about this library on charmhub.

Integration example

With both libraries loki_push_api and log_proxy the following integration can be done:

┌──────────────────┐  Workload logs  ┌────────────────────┐  Workloads logs ┌──────────────────┐
│                  │ ───────────────►│                    │ ───────────────►│                  │
│ Custom Workload  │                 │  Grafana agent     │                 │ Loki             │
│                  ├─────────────────┤                    ├─────────────────┤                  │
│ Charmed Operator │ loki_push_api   │  Charmed Operator  │  loki_push_api  │ Charmed Operator │
│                  │                 │                    │                 │                  │
└──────────────────┘                 └────────────────────┘                 └──────────────────┘
Uses:                                 Uses:                                  Uses:
- LogProxyConsumer                    - LokiPushApiConsumer                 - LokiPushApiProvider
                                      - LogProxyProvider

Loki charmed Operator Integrations

  1. Loki integrates with Grafana, providing a data source for viewing logs stored by Loki. This data source may then be consumed in dashboards provided by other charms relating to Grafana.

  2. Loki forwards alerts to one or more Alertmanagers that are related to it.