[jira] [Created] (SOLR-14566) Record "NOW" on "coordinator" log messages

["Jason Gerlowski (Jira)" <ji...@apache.org>]

Jason Gerlowski created SOLR-14566:
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             Summary: Record "NOW" on "coordinator" log messages
                 Key: SOLR-14566
                 URL: https://issues.apache.org/jira/browse/SOLR-14566
             Project: Solr
          Issue Type: Improvement
      Security Level: Public (Default Security Level. Issues are Public)
            Reporter: Jason Gerlowski
            Assignee: Jason Gerlowski


Currently, in SolrCore.java we log each search request that comes through each core as it is finishing.  This includes the path, query-params, QTime, and status.  In the case of a distributed search both the "coordinator" node and each of the per-shard requests produce a log message.

When Solr is fielding many identical queries, such as those created by a healthcheck or dashboard, it can be hard when examining logs to link the per-shard requests with the "cooordinator" request that came in upstream.

One thing that would make this easier is if the {{NOW}} param added to per-shard requests is also included in the log message from the "coordinator".  While {{NOW}} isn't unique strictly speaking, it often is in practice, and along with the query-params would allow debuggers to associate shard requests with coordinator requests a large majority of the time.

An alternative approach would be to create a {{qid}} or {{query-uuid}} when the coordinator starts its work that can be logged everywhere.  This provides a stronger expectation around uniqueness, but would require UUID generation on the coordinator, which may be non-negligible work at high QPS (maybe? I have no idea).  It also loses the neatness of reusing data already present on the shard requests.  



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