grafana/docs/sources/reference/templating.md

+++ title = "Templating" keywords = ["grafana", "templating", "documentation", "guide"] type = "docs" [menu.docs] name = "Templating" parent = "dashboard_features" weight = 1 +++

Templating

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

Checkout the [Templating]({{< relref "reference/templating.md" >}}) documentation for an introduction to the templating feature and the different types of template variables.

Templating allows for more interactive and dynamic dashboards. Instead of hard-coding things like server, application and sensor name in you metric queries you can use variables in their place. Variables are shown as dropdown select boxes at the top of the dashboard. These dropdowns makes it easy to change the data being displayed in your dashboard.

What is a variable?

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 dropdown at the top of the dashboard, your panel's metric queries will change to reflect the new value.

Interpolation

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

• $<varname> Example: apps.frontend.$server.requests.count
• [[varname]] Example: apps.frontend.server.requests.count

Why two ways? The first syntax is easier to read and write but does not allow you to use a variable in the middle of word. Use the second syntax in expressions like my.server[[serverNumber]].count.

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 article for details on value escaping during interpolation.

Variable options

A variable is presented as a dropdown select box at the top of the dashboards. It has a current value and a set of options. The options is the the set of values you can choose from.

Adding a variable

You add variables via Dashboard cogs menu > Templating. This opens up a list of variables and a New button to create a new variable.

Basic variable options

Option	Description
Name	The name of the variable, this is the name you use when you refer to your variable in your metric queries. Must be unique and contain no white-spaces.
Label	The name of the dropdown for this variable.
Hide	Options to hide the dropdown select box.
Type	Defines the variable type.

Variable types

Type	Description
Query	This variable type allows you to write a data source query that usually returns a list of metric names, tag values or keys. For example a query that returns a list of server names, sensor ids or data centers.
Interval	This variable can represent timespans. Instead of hard-coding a group by time or date histogram interval use a variable of this type.
Datasource	This type allows you to quickly change data source for an entire Dashboard. Useful if you have multiple instances of a data source in for example different environments.
Custom	Define the variable options manually using a comma seperated list.
Constant	Define a hidden constant. Useful for metric path prefixes for dashboards you want to share. During dashboard export constant variables will be made into an import option.
Ad hoc filters	Very special kind of variable that only works with some data sources, InfluxDB & Elasticsearch currently. It allows you to add key/value filters that will automatically be added to all metric queries that use the specified data source.

Query options

This variable type is the most powerful and complex as it can dynamically fetch its options using a data source query.

Option	Description
Data source	The data source target for the query.
Refresh	Controls when to update the variable option list (values in the dropdown). On Dashboard Load will slow down dashboard load as the variable query needs to be completed before dashboard can be initialized. Set this only to On Time Range Change if your variable options query contains a time range filter or is dependant on dashboard time range.
Query	The data source specific query expression.
Regex	Regex to filter or capture specific parts of the names return by your data source query. Optional.
Sort	Define sort order for options in dropdown. Disabled means that the order of options returned by your data source query will be used.

Query expressions

The query expressions are different for each data source.

• [Graphite templating queries]({{< relref "features/datasources/graphite.md#templating" >}})
• [Elasticsearch templating queries]({{< relref "features/datasources/elasticsearch.md#templating" >}})
• [InfluxDB templating queries]({{< relref "features/datasources/influxdb.md#templating" >}})
• [Prometheus templating queries]({{< relref "features/datasources/prometheus.md#templating" >}})
• [OpenTSDB templating queries]({{< relref "features/datasources/prometheus.md#templating" >}})

One thing to note is that query expressions can contain references to other variables and in effect create depend & nested variables. Grafana will detect this and automatically refresh a variable when one of it's containing variables change.

Selection Options

Option	Description
Mulit-value	If enabled, the variable will support the selection of multiple options at the same time.
Include All option	Add a special All option whose value includes all options.
Custom all value	By default the All value will include all options in combined expression. This can become very long and can have performance problems. Many times it can be better to specify a custom all value, like a wildcard regex. To make it possible to have custom regex, globs or lucene syntax in the Custom all value option it is never escaped so you will have to think avbout what is a valid value for your data source.

Formating multiple values

Interpolating a variable with multiple values selected is tricky as it is not straight forward how to format the multiple values to into a string that is valid in the given context where the variable is used. Grafana tries to solve this by allowing each data source plugin to inform the templating interpolation engine what format to use for multiple values.

Graphite for example uses glob expressions. A variable with multiple values would in this case be interpolated as {host1,host2,host3} if the current variable value was host1, host2 and host3.

InfluxDB and Prometheus uses regex expressions, so the same variable would be interpolated as (host1|host2|host3). Every value would also be regex escaped, if not, a value with a regex control character would break the regex expression.

Elasticsearch uses lucene query syntax, so the same variable would in this case be formated as ("host1" OR "host2" OR "host3"). In this case every value needs to be escaped so that the value can contain lucene control words and quotation marks.

Formating troubles

Automatic escaping & formating can cause problems and it can be tricky to grasp the logic is behind it. Especially for InfluxDB and Prometheus where the use of regex syntax requires that the variable is used in regex operator context. If you do not want Grafana to do this automatic regex escaping and formating your only option is to disable the Multi-value or Include All option options.

Value groups/tags

If you have a lot of options in the dropdown for a multi-value variable. You can use this feature to group the values into selectable tags.

Option	Description
Tags query	Data source query that should return a list of tags
Tag values query	Data source query that should return a list of values for a specified tag key. Use $tag in the query to refer the currently selected tag.

Interval variables

Use the Interval type to create a variable that represent a timespan (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 parameter to group by time (for InfluxDB), Date histogram interval (for Elasticsearch) or as a summarize function parameter (for Graphite).

Repeating Panels

Template variables can be very useful to dynamically change your queries across a whole dashboard. If you want Grafana to dynamically create new panels or rows based on what values you have selected you can use the Repeat feature.

If you have a variable with Multi-value or Include all value options enabled you can choose one panel or one row and have Grafana repeat that row for every selected value. You find this option under the General tab in panel edit mode. You select the variable to repeat by, and a min span. The min span controls how small Grafana will make the panels (if you have many values selected). Grafana will automatically adjust the width of each repeated panel so that the whole row is filled. Currently you cannot mix other panels on a row with a repeated panel.

Only make changes to the first panel (the original template). To have the changes take effect on all panels you need to trigger a dynamic dashboard re-build. You can do this by either changing the variable value (that is the basis for the repeat) or reload the dashboard.

Repeating Rows

This option requires you to open the row options view. Hover over the row left side to trigger the row menu, in this menu click Row Options. This opens the row options view. Here you find a Repeat dropdown where you can select the variable to repeat by.

URL state

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