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69 lines
3.5 KiB
Markdown
69 lines
3.5 KiB
Markdown
---
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aliases:
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- ../../data-sources/elasticsearch/template-variables/
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description: Using template variables with Elasticsearch in Grafana
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keywords:
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- grafana
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- elasticsearch
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- templates
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- variables
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- queries
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menuTitle: Template variables
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title: Elasticsearch template variables
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weight: 400
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---
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# Elasticsearch template variables
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Instead of hard-coding details such as server, application, and sensor names in metric queries, you can use variables.
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Grafana lists these variables in dropdown select boxes at the top of the dashboard to help you change the data displayed in your dashboard.
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Grafana refers to such variables as template variables.
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For an introduction to templating and template variables, refer to the [Templating]({{< relref "../../../dashboards/variables" >}}) and [Add and manage variables]({{< relref "../../../dashboards/variables/add-template-variables" >}}) documentation.
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## Choose a variable syntax
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The Elasticsearch data source supports two variable syntaxes for use in the **Query** field:
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- `$varname`, such as `hostname:$hostname`, which is easy to read and write but doesn't let you use a variable in the middle of a word.
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- `[[varname]]`, such as `hostname:[[hostname]]`
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When the _Multi-value_ or _Include all value_ options are enabled, Grafana converts the labels from plain text to a Lucene-compatible condition.
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For details, see the [Multi-value variables]({{< relref "../../../dashboards/variables/add-template-variables#multi-value-variables" >}}) documentation.
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## Use variables in queries
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You can use other variables inside the query.
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This example is used to define a variable named `$host`:
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```
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{"find": "terms", "field": "hostname", "query": "source:$source"}
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```
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This uses another variable named `$source` inside the query definition.
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Whenever you change the value of the `$source` variable via the dropdown, Grafana triggers an update of the `$host` variable to contain only hostnames filtered by, in this case, the `source` document property.
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These queries by default return results in term order (which can then be sorted alphabetically or numerically as for any variable).
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To produce a list of terms sorted by doc count (a top-N values list), add an `orderBy` property of "doc_count".
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This automatically selects a descending sort.
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{{% admonition type="note" %}}
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To use an ascending sort (`asc`) with doc_count (a bottom-N list), set `order: "asc"`. However, Elasticsearch [discourages this](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-bucket-terms-aggregation.html#search-aggregations-bucket-terms-aggregation-order) because sorting by ascending doc count can return inaccurate results.
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{{% /admonition %}}
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To keep terms in the doc count order, set the variable's Sort dropdown to **Disabled**.
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You can alternatively use other sorting criteria, such as **Alphabetical**, to re-sort them.
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```
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{"find": "terms", "field": "hostname", "orderBy": "doc_count"}
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```
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## Template variable examples
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{{< figure src="/static/img/docs/elasticsearch/elastic-templating-query-7-4.png" max-width="500px" class="docs-image--no-shadow" caption="Query with template variables" >}}
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In the above example, a Lucene query filters documents based on the `hostname` property using a variable named `$hostname`.
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The example also uses a variable in the _Terms_ group by field input box, which you can use to quickly change how data is grouped.
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To view an example dashboard on Grafana Play, see the [Elasticsearch Templated Dashboard](https://play.grafana.org/d/z8OZC66nk/elasticsearch-8-2-0-sample-flight-data?orgId=1).
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