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Templates and variables

A variable is a placeholder for a value. You can use variables in metric queries and in panel titles. So when you change the value, using the drop-down list at the top of the dashboard, your panel’s metric queries will change to reflect the new value.

Variables allow you to create more interactive and dynamic dashboards. Instead of hard-coding things like server, application, and sensor names in your metric queries, you can use variables in their place. Variables are displayed as drop-down lists at the top of the dashboard. These drop-downs make it easy to change the data being displayed in your dashboard.

These can be especially useful for administrators who want to allow Grafana viewers to quickly adjust visualizations but do not want to give them full editing permissions. Grafana Viewers can use variables.

Variables and templates also allow you to single-source dashboards. If you have multiple identical data sources or servers, you can make one dashboard and use variables to change what you are viewing. This simplifies maintenance and upkeep enormously.

Templates

A template is any query that contains a variable.

For example, if you were administering a dashboard to monitor several servers, you could make a dashboard for each server. Or you could create one dashboard and use panels with template queries like this one:

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wmi_system_threads{instance=~"$server"}

Variable values are always synced to the URL using the syntax var-<varname>=value.

Examples of templates and variables

To see variable and template examples, go to any of the dashboards listed below.

• Elasticsearch Templated dashboard
• Graphite Templated Nested dashboard
• InfluxDB Templated dashboard

Variables are listed in dropdown lists across the top of the screen. Select different variables to see how the visualizations change.

To see variable settings, navigate to Dashboard Settings > Variables. Click a variable in the list to see its settings.

Variables can be used in titles, descriptions, text panels, and queries. Queries with text that starts with $ are templates. Not all panels will have template queries.

Variable syntax

Panel titles and metric queries can refer to variables using two different syntaxes:

• $varname This syntax is easy to read, but it does not allow you to use a variable in the middle of a word. Example: apps.frontend.$server.requests.count
• ${var_name} Use this syntax when you want to interpolate a variable in the middle of an expression.
• ${var_name:<format>} This format gives you more control over how Grafana interpolates values. Refer to Advanced variable format options for more detail on all the formatting types.
• [[varname]] Do not use. Deprecated old syntax, will be removed in a future release.

Before queries are sent to your data source the query is interpolated, meaning the variable is replaced with its current value. During interpolation, the variable value might be escaped in order to conform to the syntax of the query language and where it is used. For example, a variable used in a regex expression in an InfluxDB or Prometheus query will be regex escaped. Read the data source specific documentation topic for details on value escaping during interpolation.

For advanced syntax to override data source default formatting, refer to Advanced variable format options.

Variable types

Grafana has global built-in variables that can be used in expressions in the query editor. Refer to Global variables for more information.

You can also define the following types of variables in Grafana.

Query

Query variables allow you to write a data source query that might return a list of metric names, tag values, keys, server names, sensor IDs, data centers, etc.

For instructions, refer to Add a query variable.

Queries can contain other variables. For more information, refer to Chained variables.

Custom

Define the variable options manually using a comma-separated list.

Text box

Text box variables display as a free text input field with an optional default value.

Constant

Define a hidden constant. Useful for metric path prefixes for dashboards you want to share. During dashboard export, constant variables are made into an import option.

Data source

Data source variables allow you to quickly change the data source for an entire dashboard. Useful if you have multiple instances of a data source in for example different environments.

Interval

Interval variables represent time spans. Instead of hard-coding a group by time or date histogram interval, use an interval variable.

You can use the Interval type to create a variable that represents a time span (eg. 1m,1h, 1d). There is also a special auto option that will change depending on the current time range. You can specify how many times the current time range should be divided to calculate the current auto timespan.

This variable type is useful as a parameter to group by time (for InfluxDB), Date histogram interval (for Elasticsearch) or as a summarize function parameter (for Graphite).

Example using the template variable myinterval of type Interval in a Graphite function:

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summarize($myinterval, sum, false)

Ad hoc filters

Ad hoc filter variables only work with InfluxDB, Prometheus, and Elasticsearch data sources. This variable type allows you to add key/value filters that are automatically added to all metric queries that use the specified data source.

Variable best practices

• Variable drop-down lists are displayed in the order they are listed in the variable list in Dashboard settings. Consider putting the variables that you will change often at the top, so they will be shown first (far left on the dashboard).