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# 18 Prometheus checks

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#### Overview

Zabbix can query metrics exposed in the Prometheus line format.

Two steps are required to start gathering Prometheus data:

-   an [HTTP master item](/manual/config/items/itemtypes/http) pointing
    to the appropriate data endpoint, e.g.
    `https://<prometheus host>/metrics`
-   dependent items using a Prometheus preprocessing option to query
    required data from the metrics gathered by the master item

There are two Prometheus data preprocessing options:

-   *Prometheus pattern* - used in normal items to query Prometheus data
-   *Prometheus to JSON* - used in normal items and for low-level
    discovery. In this case queried Prometheus data are returned in a
    JSON format.

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#### Configuration

Providing you have the HTTP master item configured, you need to create a
[dependent item](/manual/config/items/itemtypes/dependent_items) that
uses Prometheus preprocessing step:

-   enter general dependent item parameters in the configuration form
-   go to the Preprocessing tab
-   select a *Prometheus* preprocessing option (*Prometheus pattern* or
    *Prometheus to JSON*)

![](../../../../../assets/en/manual/config/items/itemtypes/prometheus_item1.png){width="600"}

|Parameter|Description|Examples|
|---------|-----------|--------|
|*Pattern*|To define the required data pattern you may use a query language that is similar to Prometheus query language (see [comparison table](#query_language_comparison)), e.g.:<br><metric name> - select by metric name<br>{\_\_name\_\_="<metric name>"} - select by metric name<br>{\_\_name\_\_=\~"<regex>"} - select by metric name matching a regular expression<br>{<label name>="<label value>",...} - select by label name<br>{<label name>=\~"<regex>",...} - select by label name matching a regular expression<br>{\_\_name\_\_=\~".\*"}==<value> - select by metric value<br>Or a combination of the above:<br><metric name>{<label1 name>="<label1 value>",<label2 name>=\~"<regex>",...}==<value><br><br>Label value can be any sequence of UTF-8 characters, but the backslash, double-quote and line feed characters have to be escaped as `\\`, `\"` and `\n` respectively; other characters shall not be escaped.|*wmi\_os\_physical\_memory\_free\_bytes*<br>*cpu\_usage\_system{cpu="cpu-total"}*<br>*cpu\_usage\_system{cpu=\~".\*"}*<br>*cpu\_usage\_system{cpu="cpu-total",host=\~".\*"}*<br>*wmi\_service\_state{name="dhcp"}==1*<br>*wmi\_os\_timezone{timezone=\~".\*"}==1*|
|*Output*|Define label name (optional). In this case the value corresponding to the label name is returned.<br>This field is only available for the *Prometheus pattern* option.|<|

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#### Prometheus to JSON

Data from Prometheus can be used for low-level discovery. In this case
data in JSON format are needed and the *Prometheus to JSON*
preprocessing option will return exactly that.

For more details, see [Discovery using Prometheus
data](/manual/discovery/low_level_discovery/prometheus).

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#### Query language comparison

The following table lists differences and similarities between PromQL
and Zabbix Prometheus preprocessing query language.

|<|[PromQL instant vector selector](https://prometheus.io/docs/prometheus/latest/querying/basics/#instant-vector-selectors)|Zabbix Prometheus preprocessing|
|-|------------------------------------------------------------------------------------------------------------------------|-------------------------------|
|**Differences**|<|<|
|Query target|Prometheus server|Plain text in Prometheus exposition format|
|Returns|Instant vector|Metric or label value (Prometheus pattern)<br>Array of metrics for single value in JSON (Prometheus to JSON)|
|Label matching operators|**=**, **!=**, **=\~**, **!\~**|**=**, **=\~**|
|Regular expression used in label or metric name matching|RE2|PCRE|
|Comparison operators|See [list](https://prometheus.io/docs/prometheus/latest/querying/operators/#comparison-binary-operators)|Only **==** (equal) is supported for value filtering|
|**Similarities**|<|<|
|Selecting by metric name that equals string|<metric name> or {\_\_name\_\_="<metric name>"}|<metric name> or {\_\_name\_\_="<metric name>"}|
|Selecting by metric name that matches regular expression|{\_\_name\_\_=\~"<regex>"}|{\_\_name\_\_=\~"<regex>"}|
|Selecting by <label name> value that equals string|{<label name>="<label value>",...}|{<label name>="<label value>",...}|
|Selecting by <label name> value that matches regular expression|{<label name>=\~"<regex>",...}|{<label name>=\~"<regex>",...}|
|Selecting by value that equals string|{\_\_name\_\_=\~".\*"} == <value>|{\_\_name\_\_=\~".\*"} == <value>|

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