[jira] [Commented] (SOLR-9824) Documents indexed in bulk are replicated using too many HTTP requests

["David Smiley (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SOLR-9824?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15717028#comment-15717028 ] 

David Smiley commented on SOLR-9824:
------------------------------------

Work-around: Thanks to some additional conditions of when the lastDocInBatch condition happens, it's possible to work-around this performance bug by setting {{-Dsolr.cloud.replication.runners=2}} (not 1).  I don't really like it at 2 but since it fixes the bug, I'm going with it.  In addition, in my environment I've set {{-Dsolr.cloud.replication.poll-queue-time-ms=1000}}; the default is 25.

solr.cloud.replication.poll-queue-time-ms:  The fact that this defaults to a measly 25ms is too low IMO.  I think it should be at least 250 -- which happens to be the default in ConcurrentUpdateSolrClient.  The lower it is, the greater likelihood of more indexing overhead including log messages.  The greater it is, it could delay a /update connection from completing up to this amount of time.

AddUpdateCommand.pollQueueTime defaults to 0, which is only modified to {{-Dsolr.cloud.replication.poll-queue-time-ms=25}} by javabin.  So if you send data to Solr in anything other than javabin, boy are you in for some HTTP connection frenzy (I've tried).  I insist we set this to a reasonable number.  Perhaps 250 as per my other suggestion, and overridable using the same system property.

> Documents indexed in bulk are replicated using too many HTTP requests
> ---------------------------------------------------------------------
>
>                 Key: SOLR-9824
>                 URL: https://issues.apache.org/jira/browse/SOLR-9824
>             Project: Solr
>          Issue Type: Improvement
>      Security Level: Public(Default Security Level. Issues are Public) 
>          Components: SolrCloud
>    Affects Versions: 6.3
>            Reporter: David Smiley
>
> This takes awhile to explain; bear with me. While working on bulk indexing small documents, I looked at the logs of my SolrCloud nodes.  I noticed that shards would see an /update log message every ~6ms which is *way* too much.  These are requests from one shard (that isn't a leader/replica for these docs but the recipient from my client) to the target shard leader (no additional replicas).  One might ask why I'm not sending docs to the right shard in the first place; I have a reason but it's besides the point -- there's a real Solr perf problem here and this probably applies equally to replicationFactor>1 situations too.  I could turn off the logs but that would hide useful stuff, and it's disconcerting to me that so many short-lived HTTP requests are happening, somehow at the bequest of DistributedUpdateProcessor.  After lots of analysis and debugging and hair pulling, I finally figured it out.  
> In SOLR-7333 ([~tpot]) introduced an optimization called {{UpdateRequest.isLastDocInBatch()}} in which ConcurrentUpdateSolrClient will poll with a '0' timeout to the internal queue, so that it can close the connection without it hanging around any longer than needed.  This part makes sense to me.  Currently the only spot that has the smarts to set this flag is {{JavaBinUpdateRequestCodec.unmarshal.readOuterMostDocIterator()}} at the last document.  So if a shard received docs in a javabin stream (but not other formats) one would expect the _last_ document to have this flag.  There's even a test.  Docs without this flag get the default poll time; for javabin it's 25ms.  Okay.
> I _suspect_ that if someone used CloudSolrClient or HttpSolrClient to send javabin data in a batch, the intended efficiencies of SOLR-7333 would apply.  I didn't try. In my case, I'm using ConcurrentUpdateSolrClient (and BTW DistributedUpdateProcessor uses CUSC too).  CUSC uses the RequestWriter (defaulting to javabin) to send each document separately without any leading marker or trailing marker.  For the XML format by comparison, there is a leading and trailing marker (<stream> ... </stream>).  Since there's no outer container for the javabin unmarshalling to detect the last document, it marks _every_ document as {{req.lastDocInBatch()}}!  Ouch!



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@lucene.apache.org
For additional commands, e-mail: dev-help@lucene.apache.org