Monitoring Solr with Prometheus and Grafana

If you use Prometheus and Grafana for metrics storage and data visualization, Solr includes a Prometheus exporter to collect metrics and other data.

A Prometheus exporter (solr-exporter) allows users to monitor not only Solr metrics which come from Metrics API, but also facet counts which come from Searching and responses to Collections API commands and PingRequestHandler requests.

This graphic provides a more detailed view:

image
Figure 1. solr-exporter Diagram
Note
This feature is considered experimental, meaning future improvements may break compatibility.

The Prometheus exporter is included in Solr as a contrib, and is located in contrib/prometheus-exporter in your Solr instance.

There are three aspects to running solr-exporter:

  • Modify the solr-exporter-config.xml to define the data to collect. Solr has a default configuration you can use, but if you would like to modify it before running the exporter the first time, see the section below Exporter Configuration.

  • Start the exporter from within Solr. See the section below Starting the Exporter.

  • Modify your Prometheus configuration to listen on the correct port. See the section below Prometheus Configuration

Starting the Exporter

You can start solr-exporter by running ./bin/solr-exporter (Linux) or .\bin\solr-exporter.cmd (Windows) from the contrib/prometheus-exporter directory.

See the commands below depending on your operating system and Solr operating mode:

Linux

Standalone mode
$ cd contrib/prometheus-exporter
$ ./bin/solr-exporter -p 9854 -b http://localhost:8983/solr -f ./conf/solr-exporter-config.xml -n 8
SolrCloud mode
$ cd contrib/prometheus-exporter
$ ./bin/solr-exporter -p 9854 -z localhost:2181/solr -f ./conf/solr-exporter-config.xml -n 16

Windows

Standalone mode
> cd contrib\prometheus-exporter
> .\bin\solr-exporter.cmd -p 9854 -b http://localhost:8983/solr -f .\conf\solr-exporter-config.xml -n 8
SolrCloud mode
> cd contrib\prometheus-exporter
> .\bin\solr-exporter -p 9854 -z localhost:2181/solr -f .\conf\solr-exporter-config.xml -n 16

Command Line Parameters

The parameters in the example start commands shown above

h, --help

Displays command line help and usage.

-p, --port

The port where Prometheus will listen for new data. This port will be used to configure Prometheus. It can be any port not already in use on your server. The default is 9983.

-b, --baseurl

The Solr base URL (such as http://localhost:8983/solr) when Solr is running in Standalone mode. If you are running Solr in SolrCloud mode, do not specify this parameter. If neither the -b parameter nor the -z parameter are defined, the default is -b http://localhost:8983/solr.

-z, --zkhost

The ZooKeeper connect string (such as localhost:8983, or localhost:2181/solr) when Solr is running in SolrCloud mode. If you are running Solr in Standalone mode, do not specify this parameter. If neither the -b parameter nor the -z parameter are defined, the -b parameter default is used.

-f, --config-file

The path to the configuration file that defines the Solr metrics to read. The default is contrib/prometheus-exporter/conf/solr-exporter-config.xml.

-n, --num-threads

The number of threads. The solr-exporter creates thread pools for requests to Solr. Request latency can be improved by increasing the number of threads. The default is 1.

The Solr’s metrics exposed by solr-exporter can be seen at: http://localhost:9983/solr/admin/metrics.

Exporter Configuration

The configuration for the solr-exporter defines the data to get from Solr. This includes the metrics, but can also include queries to the PingRequestHandler, the Collections API, and a query to any query request handler.

A default example configuration is in contrib/prometheus-exporter/config/solr-exporter-config.xml. Below is a slightly shortened version of it:

<config>

  <rules>

    <ping>
      <lst name="request">
        <lst name="query">
          <str name="path">/admin/ping</str>
        </lst>
        <arr name="jsonQueries">
          <str>
            . as $object | $object |
            (if $object.status == "OK" then 1.0 else 0.0 end) as $value |
            {
              name         : "solr_ping",
              type         : "GAUGE",
              help         : "See following URL: https://lucene.apache.org/solr/guide/ping.html",
              label_names  : [],
              label_values : [],
              value        : $value
            }
          </str>
        </arr>
      </lst>
    </ping>

    <metrics>
      <lst name="request">
        <lst name="query">
          <str name="path">/admin/metrics</str>
          <lst name="params">
            <str name="group">all</str>
            <str name="type">all</str>
            <str name="prefix"></str>
            <str name="property"></str>
          </lst>
        </lst>
        <arr name="jsonQueries">
          <!--
            jetty metrics
          -->
          <str>
            .metrics["solr.jetty"] | to_entries | .[] | select(.key | startswith("org.eclipse.jetty.server.handler.DefaultHandler")) | select(.key | endswith("xx-responses")) as $object |
            $object.key | split(".") | last | split("-") | first as $status |
            $object.value.count as $value |
            {
            name         : "solr_metrics_jetty_response_total",
            type         : "COUNTER",
            help         : "See following URL: https://lucene.apache.org/solr/guide/metrics-reporting.html",
            label_names  : ["status"],
            label_values : [$status],
            value        : $value
            }
          </str>
...
        </arr>
      </lst>
    </metrics>

    <collections>
      <lst name="request">
        <lst name="query">
          <str name="path">/admin/collections</str>
          <lst name="params">
            <str name="action">CLUSTERSTATUS</str>
          </lst>
        </lst>
        <arr name="jsonQueries">
          <str>
            .cluster.live_nodes | length as $value|
            {
              name         : "solr_collections_live_nodes",
              type         : "GAUGE",
              help         : "See following URL: https://lucene.apache.org/solr/guide/collections-api.html#clusterstatus",
              label_names  : [],
              label_values : [],
              value        : $value
            }
          </str>
...
        </arr>
      </lst>
    </collections>

    <search>
      <lst name="request">
        <lst name="query">
          <str name="collection">collection1</str>
          <str name="path">/select</str>
          <lst name="params">
            <str name="q">*:*</str>
            <str name="start">0</str>
            <str name="rows">0</str>
            <str name="json.facet">
              {
                category: {
                  type: terms,
                  field: cat
                }
              }
            </str>
          </lst>
        </lst>
        <arr name="jsonQueries">
          <str>
            .facets.category.buckets[] as $object |
            $object.val as $term |
            $object.count as $value |
            {
              name         : "solr_facets_category",
              type         : "GAUGE",
              help         : "Category facets",
              label_names  : ["term"],
              label_values : [$term],
              value        : $value
            }
          </str>
        </arr>
      </lst>
    </search>

  </rules>

</config>

Configuration Tags and Elements

The solr-exporter works by making a request to Solr according to the definitions in the configuration file, scraping the response, and converting it to a JSON structure Prometheus can understand. The configuration file defines the elements to request, how to scrape them, and where to place the extracted data in the JSON template.

The solr-exporter configuration file always starts and closes with two simple elements:

<config>
  <rules>

  </rules>
</config>

Between these elements, the data the solr-exporter should request is defined. There are several possible types of requests to make:

<ping>

Scrape the response to a PingRequestHandler request.

<metrics>

Scrape the response to a Metrics API request.

<collections>

Scrape the response to a Collections API request.

<search>

Scrape the response to a search request.

Within each of these types, we need to define the query and how to work with the response. To do this, we define two additional elements:

<query>

Defines the query parameter(s) used for the request. This section uses several additional properties to define your query:

collection

The collection to issue the query against. Only used in SolrCloud mode.

core

The core to issue the query against. Only used in Standalone mode.

path

The path to the query endpoint where the request will be sent. Examples include admin/metrics or /select or admin/collections.

params

Additional query parameters. These will vary depending on the request type and the endpoint. For example, if using the Metrics endpoint, you can add parameters to limit the query to a certain group and/or prefix. If you’re using the Collections API, the command you want to use would be a parameter.

<jsonQueries>

This is an array that defines one or more JSON Queries in jq syntax. For more details about how to structure these queries, see the jq user manual.

A jq query has to output JSON in the following format:

{
  "name": "solr_ping",
  "type": "GAUGE",
  "help": "See following URL: https://lucene.apache.org/solr/guide/ping.html",
  "label_names": ["base_url","core"],
  "label_values": ["http://localhost:8983/solr","collection1"],
  "value": 1.0
}

See the section Exposition Format below for information about what information should go into each property, and an example of how the above example is translated for Prometheus.

Exposition Format

The solr-exporter converts the JSON to the following exposition format:

# TYPE <name> <type>
# HELP <name> <help>
<name>{<label_names[0]>=<label_values[0]>,<label_names[1]>=<labelvalues[1]>,...} <value>

The following parameters should be set:

name

The metric name to set. For more details, see Prometheus naming best practices.

type

The type of the metric, can be COUNTER, GAUGE, SUMMARY, HISTOGRAM or UNTYPED. For more details, see Prometheus metric types.

help

Help text for the metric.

label_names

Label names for the metric. For more details, see Prometheus naming best practices.

label_values

Label values for the metric. For more details, see Prometheus naming best practices.

value

Value for the metric. Value must be set to Double type.

For example, solr-exporter converts the JSON in the previous section to the following:

# TYPE solr_ping gauge
# HELP solr_ping See following URL: https://lucene.apache.org/solr/guide/ping.html
solr_ping{base_url="http://localhost:8983/solr",core="collection1"} 1.0

Prometheus Configuration

In order for Prometheus to know about the solr-exporter, the listen address must be added to prometheus.yml, as in this example:

scrape_configs:
  - job_name: 'solr'
    static_configs:
      - targets: ['localhost:9854']

If you already have a section for scrape_configs, you can add the job_name and other values in the same section.

When you apply the settings to Prometheus, it will start to pull Solr’s metrics from solr-exporter.

Sample Grafana Dashboard

A Grafana sample dashboard is provided in the following JSON file: contrib/prometheus-exporter/conf/grafana-solr-dashboard.json. You can place this with your other Grafana dashboard configurations and modify it as necessary depending on any customization you’ve done for the solr-exporter configuration.

This screenshot shows what it might look like:

image
Figure 2. Grafana Dashboard