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From Douglas Rapp <dougma...@gmail.com>
Subject Problems using MapReduceIndexerTool with multiple reducers
Date Tue, 12 Jan 2016 00:18:52 GMT
Hello,

I am using Solr 4.10.4 in SolrCloud mode, but so far with only a single
instance (so just a single shard - not very cloud-like..).

I have been experimenting using the MapReduceIndexerTool to handle batch
indexing of CSV files in HDFS. I got it working on a weaker single-node
Hadoop test system, so I have been trying to do some performance testing on
a 4-node Hadoop cluster (1 NameNode, 3 DataNode) with better hardware. The
issue that I have come across is that the job will only finish successfully
if I specify a single reducer (using the "--reducers 1" option upon
invoking the tool).

If the tool is invoked without specifying a number for mappers/reducers, it
appears that it tries to utilize the maximum number available. In my case,
it tries to use 16 mappers and 6 reducers. I have tried specifying many
different combinations, and what I have found is that I can tweak the
number of mappers to just about anything, but reducers must stay at "1" or
else the job fails. Also explains why I never saw this pop up on the first
system - looking closer at it, it defaults to only 1 reducer there. If I
try to increase it, I get the same failure. When the job fails, I get the
following stack trace:

6602 [main] WARN  org.apache.hadoop.mapred.YarnChild  - Exception running
child : org.kitesdk.morphline.api.MorphlineRuntimeException:
java.lang.IllegalStateException: No matching slice found! The slice seems
unavailable. docRouterClass: org.apache.solr.common.cloud.ImplicitDocRouter
        at
org.kitesdk.morphline.base.FaultTolerance.handleException(FaultTolerance.java:73)
        at
org.apache.solr.hadoop.morphline.MorphlineMapRunner.map(MorphlineMapRunner.java:213)
        at
org.apache.solr.hadoop.morphline.MorphlineMapper.map(MorphlineMapper.java:86)
        at
org.apache.solr.hadoop.morphline.MorphlineMapper.map(MorphlineMapper.java:54)
        at org.apache.hadoop.mapreduce.Mapper.run(Mapper.java:145)
        at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:784)
        at org.apache.hadoop.mapred.MapTask.run(MapTask.java:341)
        at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:163)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:415)
        at
org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1628)
        at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:158)
Caused by: java.lang.IllegalStateException: No matching slice found! The
slice seems unavailable. docRouterClass:
org.apache.solr.common.cloud.ImplicitDocRouter
        at
org.apache.solr.hadoop.SolrCloudPartitioner.getPartition(SolrCloudPartitioner.java:120)
        at
org.apache.solr.hadoop.SolrCloudPartitioner.getPartition(SolrCloudPartitioner.java:49)
        at
org.apache.hadoop.mapred.MapTask$NewOutputCollector.write(MapTask.java:712)
        at
org.apache.hadoop.mapreduce.task.TaskInputOutputContextImpl.write(TaskInputOutputContextImpl.java:89)
        at
org.apache.hadoop.mapreduce.lib.map.WrappedMapper$Context.write(WrappedMapper.java:112)
        at
org.apache.solr.hadoop.morphline.MorphlineMapper$MyDocumentLoader.load(MorphlineMapper.java:138)
        at
org.apache.solr.morphlines.solr.LoadSolrBuilder$LoadSolr.doProcess(LoadSolrBuilder.java:129)
        at
org.kitesdk.morphline.base.AbstractCommand.process(AbstractCommand.java:156)
        at org.kitesdk.morphline.base.Connector.process(Connector.java:64)
        at
org.kitesdk.morphline.base.AbstractCommand.doProcess(AbstractCommand.java:181)
        at
org.apache.solr.morphlines.solr.SanitizeUnknownSolrFieldsBuilder$SanitizeUnknownSolrFields.doProcess(SanitizeUnknownSolrFieldsBuilder.java:94)
        at
org.kitesdk.morphline.base.AbstractCommand.process(AbstractCommand.java:156)
        at org.kitesdk.morphline.base.Connector.process(Connector.java:64)
        at
org.kitesdk.morphline.stdio.ReadCSVBuilder$ReadCSV.doProcess(ReadCSVBuilder.java:124)
        at
org.kitesdk.morphline.stdio.AbstractParser.doProcess(AbstractParser.java:93)
        at
org.kitesdk.morphline.base.AbstractCommand.process(AbstractCommand.java:156)
        at
org.kitesdk.morphline.base.AbstractCommand.doProcess(AbstractCommand.java:181)
        at
org.kitesdk.morphline.base.AbstractCommand.process(AbstractCommand.java:156)
        at
org.apache.solr.hadoop.morphline.MorphlineMapRunner.map(MorphlineMapRunner.java:201)
        ... 10 more

When I try searching online for "No matching slice found", the only results
I get back are of the source code.. I can't seem to find anything to lead
me in the right direction.

Looking at the MapReduceIndexerTool more closely, it says that when using
more than one reducer per output shard (so in my case, >1) it will utilize
the "mtree" merge algorithm to merge the results held among several
mini-shards. I'm guessing this might have something to do with it, but I
can't find any other information on how this might be further tweaked or
debugged.

I can provide any additional information (environment settings, config
files, etc) on request. Any help would be appreciated.

Thanks,
Doug

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