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https://issues.apache.org/jira/browse/SOLR-5092?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13724396#comment-13724396
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Isaac Hebsh commented on SOLR-5092:
-----------------------------------
Question:
in HttpShardHandler, I can find the next comment:
{code}
// maps "localhost:8983|localhost:7574" to a shuffled
List("http://localhost:8983","http://localhost:7574";)
// This is primarily to keep track of what order we should use to query the
replicas of a shard
// so that we use the same replica for all phases of a distributed request.
shardToURLs = new HashMap<String,List<String>>();
{code}
why is the replica-consistency is so important? what would happen if one phase
of a distributed request will get a response from replica1 and another phase
will get a response from replica2?
I think this situation might happen in the current state, if one replica stops
to response during the distributed process.
> Send shard request to multiple replicas
> ---------------------------------------
>
> Key: SOLR-5092
> URL: https://issues.apache.org/jira/browse/SOLR-5092
> Project: Solr
> Issue Type: Improvement
> Components: clients - java, SolrCloud
> Affects Versions: 4.4
> Reporter: Isaac Hebsh
> Priority: Minor
> Labels: distributed, performance, shard, solrcloud
> Attachments: SOLR-5092.patch
>
>
> We have a case on a SolrCloud cluster. Queries takes too much QTime, due to a
> randomly slow shard request. In a noticeable part of queries, the slowest
> shard consumes more than 4 times qtime than the average.
> Of course, deep inspection of the performance factor should be made on the
> specific environment.
> But, there is one more idea:
> If shard request will be sent to all of the replicas of each shard, the
> probability of all the replicas of the same shard to be the slowest is very
> small. Obviously cluster works harder, but on a (very) low qps, it might be
> OK.
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