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https://issues.apache.org/jira/browse/SOLR-6305?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16425097#comment-16425097
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Hendrik Haddorp commented on SOLR-6305:
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I had just tested Solr 7.2.1 with an HDFS setup that had only one node. For
that I also saw that some files got created with a replication factor of 3 as
that is default on the client side if nothing else is configured while others
got created with a factor of 1, as configured on the name node. I then started
Solr with the system property "solr.hdfs.confdir" pointing to a directory
containing just the file "hdfs-site.xml". In that file I set "dfs.replication"
to 1. After that I did not find any files in HDFS anymore that had a
replication factor of 3.
It would however been nice if the replication factor could consistently being
controlled by the client side.
> Ability to set the replication factor for index files created by
> HDFSDirectoryFactory
> -------------------------------------------------------------------------------------
>
> Key: SOLR-6305
> URL: https://issues.apache.org/jira/browse/SOLR-6305
> Project: Solr
> Issue Type: Improvement
> Components: hdfs
> Environment: hadoop-2.2.0
> Reporter: Timothy Potter
> Priority: Major
> Attachments:
> 0001-OIQ-23224-SOLR-6305-Fixed-SOLR-6305-by-reading-the-r.patch
>
>
> HdfsFileWriter doesn't allow us to create files in HDFS with a different
> replication factor than the configured DFS default because it uses:
> {{FsServerDefaults fsDefaults = fileSystem.getServerDefaults(path);}}
> Since we have two forms of replication going on when using
> HDFSDirectoryFactory, it would be nice to be able to set the HDFS replication
> factor for the Solr directories to a lower value than the default. I realize
> this might reduce the chance of data locality but since Solr cores each have
> their own path in HDFS, we should give operators the option to reduce it.
> My original thinking was to just use Hadoop setrep to customize the
> replication factor, but that's a one-time shot and doesn't affect new files
> created. For instance, I did:
> {{hadoop fs -setrep -R 1 solr49/coll1}}
> My default dfs replication is set to 3 ^^ I'm setting it to 1 just as an
> example
> Then added some more docs to the coll1 and did:
> {{hadoop fs -stat %r solr49/hdfs1/core_node1/data/index/segments_3}}
> 3 <-- should be 1
> So it looks like new files don't inherit the repfact from their parent
> directory.
> Not sure if we need to go as far as allowing different replication factor per
> collection but that should be considered if possible.
> I looked at the Hadoop 2.2.0 code to see if there was a way to work through
> this using the Configuration object but nothing jumped out at me ... and the
> implementation for getServerDefaults(path) is just:
> public FsServerDefaults getServerDefaults(Path p) throws IOException {
> return getServerDefaults();
> }
> Path is ignored ;-)
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