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https://issues.apache.org/jira/browse/SOLR-17587?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17928258#comment-17928258
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ASF subversion and git services commented on SOLR-17587:
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Commit cc2112f93d65eef29881c1efae76db3cbef85cbf in solr's branch
refs/heads/branch_9_8 from Matthew Biscocho
[ https://gitbox.apache.org/repos/asf?p=solr.git;h=cc2112f93d6 ]
SOLR-17587: wt=prometheus fix duplicate TYPE information (#3006)
Metrics: Prometheus response writer fix for non-compliant exposition format
containing duplicate TYPE lines
9x backport of main:
* SOLR-17587: wt=prometheus fix duplicate TYPE information (#2902)
> Prometheus Writer duplicate TYPE information in exposition format
> -----------------------------------------------------------------
>
> Key: SOLR-17587
> URL: https://issues.apache.org/jira/browse/SOLR-17587
> Project: Solr
> Issue Type: Bug
> Affects Versions: 9.7
> Reporter: Matthew Biscocho
> Priority: Minor
> Labels: pull-request-available
> Fix For: 9.9
>
> Time Spent: 3h
> Remaining Estimate: 0h
>
> Solr's Prometheus writer duplicates `# TYPE <metric name> <prometheus metric
> type>` in it's exposition format for core registry metrics.
> For example this appears twice in it's output:
> {code:java}
> # TYPE solr_metrics_core_average_request_time gauge
> solr_metrics_core_average_request_time{category="ADMIN",collection="foo",core="core_foo_shard9_replica_t351",handler="/admin/file",replica="replica_t351",shard="shard9"}
> 0.0
> ...
> # TYPE solr_metrics_core_average_request_time gauge{code}
> This is technically not allowed per [Prometheus Exposition
> format|https://github.com/prometheus/docs/blob/main/content/docs/instrumenting/exposition_formats.md#:~:text=Only%20one%20TYPE%20line%20may%20exist%20for%20a%20given%20metric%20name.]
> This happens because each Dropwizard registry is per core, but for Prometheus
> compatible exposition format upon exporting, it needs to be 1 registry for
> all cores on a single host, otherwise there will be duplicate `TYPE` formats
> even though all metrics are unique for its tags/attributes.
> Funnily enough, prometheus upstream collector does not do this verification
> and accepts the metrics anyways just fine Solr -> Prometheus -> Grafana.
> But depending on the technologies prometheus exposition verification, this
> will fail. For example
> [Telegraf|https://github.com/influxdata/telegraf/blob/master/plugins/inputs/prometheus/README.md]:
> {code:java}
> -12-09T16:56:01Z E! [inputs.prometheus] Error in plugin: error reading
> metrics for "http://127.0.0.1:8983/solr/admin/metrics?wt=prometheus":
> decoding response failed: text format parsing error in line 568: second TYPE
> line for metric name "solr_metrics_core_average_request_time", or TYPE
> reported after samples {code}
> This shouldn't be a blocker if you are pushing metrics to prometheus
> collector directly.
>
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