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DocumentationGrafana documentationData sourcesLoki

Loki data source

Grafana ships with built-in support for Loki, an open-source log aggregation system by Grafana Labs. This topic explains configuring and querying specific to the Loki data source.

For instructions on how to add a data source to Grafana, refer to the administration documentation. Only users with the organization administrator role can add data sources. Administrators can also configure the data source via YAML with Grafana’s provisioning system.

Once you’ve added the Loki data source, you can configure it so that your Grafana instance’s users can create queries in its query editor when they build dashboards, use Explore, and annotate visualizations.

Configure the data source

To access the data source configuration page:

1. Hover the cursor over the Configuration (gear) icon.
2. Select Data Sources.
3. Select the Loki data source.

Set the data source’s basic configuration options carefully:

Note: To troubleshoot configuration and other issues, check the log file located at /var/log/grafana/grafana.log on Unix systems, or in <grafana_install_dir>/data/log on other platforms and manual installations.

Configure derived fields

The Derived Fields configuration helps you:

• Add fields parsed from the log message
• Add a link that uses the value of the field

For example, you can link to your tracing backend directly from your logs, or link to a user profile page if the log line contains a corresponding userId. These links appear in the log details.

Note: If you use Grafana Cloud, you can request modifications to this feature by opening a support ticket in the Cloud Portal.

Each derived field consists of:

Troubleshoot interpolation

You can use a debug section to see what your fields extract and how the URL is interpolated. Select Show example log message to display a text area where you can enter a log message.

The new field with the link shown in log details:

Provision the data source

You can define and configure the data source in YAML files as part of Grafana’s provisioning system. For more information about provisioning, and for available configuration options, refer to Provisioning Grafana.

Provisioning examples

yaml Copy

apiVersion: 1

datasources:
  - name: Loki
    type: loki
    access: proxy
    url: http://localhost:3100
    jsonData:
      maxLines: 1000

Using basic authorization and a derived field:

You must escape the dollar ($) character in YAML values because it can be used to interpolate environment variables:

yaml Copy

apiVersion: 1

datasources:
  - name: Loki
    type: loki
    access: proxy
    url: http://localhost:3100
    basicAuth: true
    basicAuthUser: my_user
    jsonData:
      maxLines: 1000
      derivedFields:
        # Field with internal link pointing to data source in Grafana.
        # Right now, Grafana supports only Jaeger and Zipkin data sources as link targets.
        # datasourceUid value can be anything, but it should be unique across all defined data source uids.
        - datasourceUid: my_jaeger_uid
          matcherRegex: "traceID=(\\w+)"
          name: TraceID
          # url will be interpreted as query for the datasource
          url: '$${__value.raw}'

        # Field with external link.
        - matcherRegex: "traceID=(\\w+)"
          name: TraceID
          url: 'http://localhost:16686/trace/$${__value.raw}'
    secureJsonData:
      basicAuthPassword: test_password

Using a Jaeger data source:

In this example, the Jaeger data source’s uid value should match the Loki data source’s datasourceUid value.

Copy

datasources:
    - name: Jaeger
      type: jaeger
      url: http://jaeger-tracing-query:16686/
      access: proxy
      # UID should match the datasourceUid in derivedFields.
      uid: my_jaeger_uid

Query the data source

The Loki data source’s query editor helps you create log and metric queries that use Loki’s query language, LogQL.

For details, refer to the query editor documentation.

Use template variables

Instead of hard-coding details such as server, application, and sensor names in metric queries, you can use variables. Grafana lists these variables in dropdown select boxes at the top of the dashboard to help you change the data displayed in your dashboard. Grafana refers to such variables as template variables.

For details, see the template variables documentation.