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<h1>Apache Hadoop 0.20.2 Release Notes</h1>
<p>These release notes cover new developer and user-facing incompatibilities, important issues, features, and major improvements.</p><hr/>
<ul>
<li><aclass="externalLink"href="https://issues.apache.org/jira/browse/MAPREDUCE-826">MAPREDUCE-826</a> | <i>Trivial</i> | <b>harchive doesn’t use ToolRunner / harchive returns 0 even if the job fails with exception</b></li>
</ul>
<p>Use ToolRunner for archives job and return non zero error code on failure.</p><hr/>
<ul>
<li><aclass="externalLink"href="https://issues.apache.org/jira/browse/MAPREDUCE-112">MAPREDUCE-112</a> | <i>Blocker</i> | <b>Reduce Input Records and Reduce Output Records counters are not being set when using the new Mapreduce reducer API</b></li>
</ul>
<p>Updates of counters for reduce input and output records were added in the new API so they are available for jobs using the new API.</p><hr/>
<ul>
<li><aclass="externalLink"href="https://issues.apache.org/jira/browse/HADOOP-6231">HADOOP-6231</a> | <i>Major</i> | <b>Allow caching of filesystem instances to be disabled on a per-instance basis</b></li>
</ul>
<p>Allow a general mechanism to disable the cache on a per filesystem basis by using property fs.<schemename>.impl.disable.cache. eg. fs.har.impl.disable.cache in core-default.xml</p><hr/>
<ul>
<li><aclass="externalLink"href="https://issues.apache.org/jira/browse/MAPREDUCE-979">MAPREDUCE-979</a> | <i>Blocker</i> | <b>JobConf.getMemoryFor{Map|Reduce}Task doesn’t fallback to newer config knobs when mapred.taskmaxvmem is set to DISABLED_MEMORY_LIMIT of -1</b></li>
</ul>
<p>Added support to fallback to new task memory configuration when deprecated memory configuration values are set to disabled.</p><hr/>
<ul>
<li><aclass="externalLink"href="https://issues.apache.org/jira/browse/HDFS-677">HDFS-677</a> | <i>Blocker</i> | <b>Rename failure due to quota results in deletion of src directory</b></li>
</ul>
<p>Rename properly considers the case where both source and destination are over quota; operation will fail with error indication.</p><hr/>
<p>Bugs fixed for Hadoop archives: character escaping in paths, LineReader and file system caching.</p><hr/>
<ul>
<li><aclass="externalLink"href="https://issues.apache.org/jira/browse/HDFS-761">HDFS-761</a> | <i>Major</i> | <b>Failure to process rename operation from edits log due to quota verification</b></li>
</ul>
<p>Corrected an error when checking quota policy that resulted in a failure to read the edits log, stopping the primary/secondary name node.</p><hr/>
<ul>
<li><aclass="externalLink"href="https://issues.apache.org/jira/browse/MAPREDUCE-1068">MAPREDUCE-1068</a> | <i>Major</i> | <b>In hadoop-0.20.0 streaming job do not throw proper verbose error message if file is not present</b></li>
</ul>
<p>Fix streaming job to show proper message if file is is not present, for -file option.</p><hr/>
<ul>
<li><aclass="externalLink"href="https://issues.apache.org/jira/browse/HDFS-596">HDFS-596</a> | <i>Blocker</i> | <b>Memory leak in libhdfs: hdfsFreeFileInfo() in libhdfs does not free memory for mOwner and mGroup</b></li>
</ul>
<p>Memory leak in function hdfsFreeFileInfo in libhdfs. This bug affects fuse-dfs severely.</p><hr/>
<ul>
<li><aclass="externalLink"href="https://issues.apache.org/jira/browse/MAPREDUCE-1147">MAPREDUCE-1147</a> | <i>Blocker</i> | <b>Map output records counter missing for map-only jobs in new API</b></li>
</ul>
<p>Adds a counter to track the number of records emitted by map writing directly to HDFS i.e map tasks of job with 0 reducers.</p><hr/>
<ul>
<li><aclass="externalLink"href="https://issues.apache.org/jira/browse/MAPREDUCE-1182">MAPREDUCE-1182</a> | <i>Blocker</i> | <b>Reducers fail with OutOfMemoryError while copying Map outputs</b></li>
</ul>
<p>Modifies shuffle related memory parameters to use ‘long’ from ‘int’ so that sizes greater than maximum integer size are handled correctly</p><hr/>
<ul>
<li><aclass="externalLink"href="https://issues.apache.org/jira/browse/HDFS-781">HDFS-781</a> | <i>Blocker</i> | <b>Metrics PendingDeletionBlocks is not decremented</b></li>
</ul>
<p>Correct PendingDeletionBlocks metric to properly decrement counts.</p><hr/>
<ul>
<li><aclass="externalLink"href="https://issues.apache.org/jira/browse/HDFS-793">HDFS-793</a> | <i>Blocker</i> | <b>DataNode should first receive the whole packet ack message before it constructs and sends its own ack message for the packet</b></li>
</ul>
<p><b>WARNING: No release note provided for this change.</b></p><hr/>
<ul>
<li><aclass="externalLink"href="https://issues.apache.org/jira/browse/HADOOP-6428">HADOOP-6428</a> | <i>Major</i> | <b>HttpServer sleeps with negative values</b></li>
</ul>
<p>Corrected arithmetic error that made sleep times less than zero.</p><hr/>
<ul>
<li><aclass="externalLink"href="https://issues.apache.org/jira/browse/HADOOP-6460">HADOOP-6460</a> | <i>Blocker</i> | <b>Namenode runs of out of memory due to memory leak in ipc Server</b></li>
</ul>
<p>If an IPC server response buffer has grown to than 1MB, it is replaced by a smaller buffer to free up the Java heap that was used. This will improve the longevity of the name service.</p><hr/>
<p>Resolves the test failure by modifying the test to base it on spill counters rather than on bytes read/written. It also introduces a new configuration parameter “mapred.job.shuffle.input.buffer.percent” to provide finer grained control on the memory limit to be used during shuffle.</p><hr/>
<ul>
<li><aclass="externalLink"href="https://issues.apache.org/jira/browse/HADOOP-6498">HADOOP-6498</a> | <i>Blocker</i> | <b>IPC client bug may cause rpc call hang</b></li>
</ul>
<p>Correct synchronization error in IPC where handler thread could hang if request reader got an error.</p><hr/>
<ul>
<li><aclass="externalLink"href="https://issues.apache.org/jira/browse/MAPREDUCE-623">MAPREDUCE-623</a> | <i>Major</i> | <b>Resolve javac warnings in mapred</b></li>
</ul>
<p>Removes javac warnings by either resolving them or suppressing them (wherever resolution is not possible)</p>
