Using Loki in Grafana

BETA: Querying Loki data requires Grafana’s Explore section. Grafana v6.x comes with Explore enabled by default. In Grafana v5.3.x and v5.4.x. you need to enable Explore manually. Viewing Loki data in dashboard panels is supported in Grafana v6.4+.

Grafana ships with built-in support for Loki, Grafana’s log aggregation system. Just add it as a data source and you are ready to query your log data in Explore.

Adding the data source

  1. Open Grafana and make sure you are logged in.
  2. In the side menu under the Configuration link you should find a link named Data Sources.
  3. Click the Add data source button at the top.
  4. Select Loki from the list of data sources.

Note: If you’re not seeing the Data Sources link in your side menu it means that your current user does not have the Admin role for the current organization.

NameDescription
NameThe data source name. This is how you refer to the data source in panels, queries, and Explore.
DefaultDefault data source means that it will be pre-selected for new panels.
URLThe URL of the Loki instance, e.g., http://localhost:3100
Maximum linesUpper limit for number of log lines returned by Loki (default is 1000). Decrease if your browser is sluggish when displaying logs in Explore.

Querying Logs

Querying and displaying log data from Loki is available via Explore, and with the logs panel in dashboards. Select the Loki data source, and then enter a log query to display your logs.

Log Queries

A log query consists of two parts: log stream selector, and a search expression. For performance reasons you need to start by choosing a log stream by selecting a log label.

The Logs Explorer (the Log labels button) next to the query field shows a list of labels of available log streams. An alternative way to write a query is to use the query field’s autocomplete - you start by typing a left curly brace { and the autocomplete menu will suggest a list of labels. Press the enter key to execute the query.

Once the result is returned, the log panel shows a list of log rows and a bar chart where the x-axis shows the time and the y-axis shows the frequency/count.


Log Stream Selector

For the label part of the query expression, wrap it in curly braces {} and then use the key value syntax for selecting labels. Multiple label expressions are separated by a comma:

{app="mysql",name="mysql-backup"}

The following label matching operators are currently supported:

  • = exactly equal.
  • != not equal.
  • =~ regex-match.
  • !~ do not regex-match.

Examples:

  • {name=~"mysql.+"}
  • {name!~"mysql.+"}

The same rules that apply for Prometheus Label Selectors apply for Loki Log Stream Selectors.

Another way to add a label selector, is in the table section, clicking on the Filter button beside a label will add the label to the query expression. This even works for multiple queries and will the label selector to each query.

Search Expression

After writing the Log Stream Selector, you can filter the results further by writing a search expression. The search expression can be just text or a regex expression.

Example queries:

  • {job="mysql"} |= "error"
  • {name="kafka"} |~ "tsdb-ops.*io:2003"
  • {instance=~"kafka-[23]",name="kafka"} != "kafka.server:type=ReplicaManager"

Filter operators can be chained and will sequentially filter down the expression. The resulting log lines will satisfy every filter.

Example

{job="mysql"} |= "error" != "timeout"

The following filter types are currently supported:

  • |= line contains string.
  • != line doesn’t contain string.
  • |~ line matches regular expression.
  • !~ line does not match regular expression.

Note: For more details about LogQL, Loki’s query language, refer to the documentation

Live tailing

Loki supports Live tailing which displays logs in real-time. This feature is supported in Explore and in dashboards with a Live toggle in the query editor.

Note that Live Tailing relies on two Websocket connections: one between the browser and the Grafana server, and another between the Grafana server and the Loki server. If you run any reverse proxies, please configure them accordingly.

Note: This feature is only available in Grafana v6.3+

Log Context

When using a search expression as detailed above, you now have the ability to retrieve the context surrounding your filtered results. By clicking the Show Context link on the filtered rows, you’ll be able to investigate the log messages that came before and after the log message you’re interested in.

Note: This feature is only available in Grafana v6.3+

Templating

Instead of hard-coding things like server, application and sensor name in your metric queries, you can use variables in their place. Variables are shown as drop-down select boxes at the top of the dashboard. These drop-down boxes make it easy to change the data being displayed in your dashboard.

Checkout the Templating documentation for an introduction to the templating feature and the different types of template variables.

Annotations

You can use any non-metric Loki query as a source for annotations. Log content will be used as annotation text and your log stream labels as tags, so there is no need for additional mapping.

Note: Annotations for Loki are only available in Grafana v6.4+

Configure the data source with provisioning

You can set up the data source via config files with Grafana’s provisioning system. You can read more about how it works and all the settings you can set for data sources on the provisioning docs page

Here is an example:

apiVersion: 1

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

Here’s another with basic auth:

apiVersion: 1

datasources:
  - name: Loki
    type: loki
    access: proxy
    url: http://localhost:3100
    basicAuth: true
    basicAuthUser: my_user
    basicAuthPassword: test_password
    jsonData:
      maxLines: 1000