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https://issues.apache.org/jira/browse/SOLR-14566?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17135960#comment-17135960
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Jason Gerlowski commented on SOLR-14566:
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Interesting, I guess you could build something unique out of info about the
request. That's a third approach here, and it might end up being cheaper than
UUID generation.
I still lean towards the {{NOW}} approach a bit I think. It's clean in that
our "correlation-key" is something that's already required on downstream nodes
as-is. It doesn't need computed at all - we already have it for the downstream
nodes. And it's semantically useful to debuggers as well, to get a sense for
when the (upstream) request came in. (Though it's probably redundant with
QTime in doing that).
The only downside is that it's not strictly unique - but that should only
really be a problem if you regularly see many identical queries come in within
the same millisecond of one another.
Will think on it a bit more and see what others chime in with.
> 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
> Priority: Minor
> Time Spent: 20m
> Remaining Estimate: 0h
>
> 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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