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https://issues.apache.org/jira/browse/SOLR-1301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12981930#action_12981930
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Alexander Kanarsky edited comment on SOLR-1301 at 1/14/11 4:27 PM:
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Note for the Hadoop 0.21 users: the current patch can be used "as is" with 
0.21, but you will need to make sure to compile it with appropriate jars 
(hadoop-common-0.21.0.jar and hadoop-mapred-0.21.0.jar instead of 
hadoop-0.20.x-core.jar). Also, as a workaround, I had to put all the relevant 
jars (solr, solrj etc.) to the lib folder of the job's jar file (i.e.  
apache-solr-hadoop-xxx-dev.jar) to avoid 
InvocationTargetException/ClassNotFound exceptions I did not have with Hadoop 
0.20.

      was (Author: kanarsky):
    Note for the Hadoop 0.21 users: the current patch can be used "as is" with 
0.21, but you will need to make sure to compile it with appropriate jars 
(hadoop-common-0.21.0.jar and hadoop-mapred-0.21.0.jar instead of 
hadoop-0.20.x-core.jar). Also, as a workaround, I had to put all the relevant 
jars (solr, solrj etc.) to the lib folder of the job's jar file (i.e.  
apache-solr-hadoop-1.4.x-dev.jar) to avoid 
InvocationTargetException/ClassNotFound exceptions I did not have with Hadoop 
0.20.
  
> Solr + Hadoop
> -------------
>
>                 Key: SOLR-1301
>                 URL: https://issues.apache.org/jira/browse/SOLR-1301
>             Project: Solr
>          Issue Type: Improvement
>    Affects Versions: 1.4
>            Reporter: Andrzej Bialecki 
>             Fix For: Next
>
>         Attachments: commons-logging-1.0.4.jar, 
> commons-logging-api-1.0.4.jar, hadoop-0.19.1-core.jar, 
> hadoop-0.20.1-core.jar, hadoop.patch, log4j-1.2.15.jar, README.txt, 
> SOLR-1301-hadoop-0-20.patch, SOLR-1301-hadoop-0-20.patch, SOLR-1301.patch, 
> SOLR-1301.patch, SOLR-1301.patch, SOLR-1301.patch, SOLR-1301.patch, 
> SOLR-1301.patch, SOLR-1301.patch, SOLR-1301.patch, SOLR-1301.patch, 
> SolrRecordWriter.java
>
>
> This patch contains  a contrib module that provides distributed indexing 
> (using Hadoop) to Solr EmbeddedSolrServer. The idea behind this module is 
> twofold:
> * provide an API that is familiar to Hadoop developers, i.e. that of 
> OutputFormat
> * avoid unnecessary export and (de)serialization of data maintained on HDFS. 
> SolrOutputFormat consumes data produced by reduce tasks directly, without 
> storing it in intermediate files. Furthermore, by using an 
> EmbeddedSolrServer, the indexing task is split into as many parts as there 
> are reducers, and the data to be indexed is not sent over the network.
> Design
> ----------
> Key/value pairs produced by reduce tasks are passed to SolrOutputFormat, 
> which in turn uses SolrRecordWriter to write this data. SolrRecordWriter 
> instantiates an EmbeddedSolrServer, and it also instantiates an 
> implementation of SolrDocumentConverter, which is responsible for turning 
> Hadoop (key, value) into a SolrInputDocument. This data is then added to a 
> batch, which is periodically submitted to EmbeddedSolrServer. When reduce 
> task completes, and the OutputFormat is closed, SolrRecordWriter calls 
> commit() and optimize() on the EmbeddedSolrServer.
> The API provides facilities to specify an arbitrary existing solr.home 
> directory, from which the conf/ and lib/ files will be taken.
> This process results in the creation of as many partial Solr home directories 
> as there were reduce tasks. The output shards are placed in the output 
> directory on the default filesystem (e.g. HDFS). Such part-NNNNN directories 
> can be used to run N shard servers. Additionally, users can specify the 
> number of reduce tasks, in particular 1 reduce task, in which case the output 
> will consist of a single shard.
> An example application is provided that processes large CSV files and uses 
> this API. It uses a custom CSV processing to avoid (de)serialization overhead.
> This patch relies on hadoop-core-0.19.1.jar - I attached the jar to this 
> issue, you should put it in contrib/hadoop/lib.
> Note: the development of this patch was sponsored by an anonymous contributor 
> and approved for release under Apache License.

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