Managing Hive

Use the following procedures to manage HiveServer2 and the Hive metastore. To configure high availability for the Hive metastore, see Hive Metastore High Availability.

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Heap Size and Garbage Collection for Hive Components

Hive Component Memory Recommendations

HiveServer2 and the Hive metastore require sufficient memory in order to run correctly. The default heap size of 256 MB for each component is inadequate for production workloads. Consider the following guidelines for sizing the heap for each component, based upon your cluster size.
Number of Concurrent Connections HiveServer2 Heap Size Minimum Recommendation Hive Metastore Heap Size Minimum Recommendation
Up to 40 concurrent connections (Cloudera recommends splitting HiveServer2 into multiple instances and load balancing once you start allocating >12 GB to HiveServer2. The objective is to size to reduce impact of Java garbage collection on active processing by the service. 12 GB 12 GB
Up to 20 concurrent connections 6 GB 10 GB
Up to 10 concurrent connections 4 GB 8 GB
Single connection 2 GB 4 GB

In addition, the Beehive CLI should use a heap size of at least 2 GB.

The permGenSize should be set to 512M for all.

Configuring Heap Size and Garbage Collection for Hive Components

To configure the heap size for HiveServer2 and Hive metastore, set the -Xmx parameter in the HADOOP_OPTS variable to the desired maximum heap size in the hive-env.sh advanced configuration snippet if you use Cloudera Manager or otherwise edit /etc/hive/hive-env.sh.

To configure the heap size for the Beehive CLI, set the HADOOP_HEAPSIZE environment variable in the hive-env.sh advanced configuration snippet if you use Cloudera Manager or otherwise edit /etc/hive/hive-env.sh before starting the Beehive CLI.

The following example shows a configuration with the following settings:
  • HiveServer2 uses 12 GB heap
  • Hive metastore uses 12 GB heap
  • Hive clients use 2 GB heap
The settings to change are in bold. All of these lines are commented out (prefixed with a # character) by default. Uncomment the lines by removing the # character.
if [ "$SERVICE" = "cli" ]; then
  if [ -z "$DEBUG" ]; then
    export HADOOP_OPTS="$HADOOP_OPTS -XX:NewRatio=12 -Xmx12288m -Xms10m -XX:MaxHeapFreeRatio=40 -XX:MinHeapFreeRatio=15 -XX:+UseParNewGC -XX:-UseGCOverheadLimit"
  else
    export HADOOP_OPTS="$HADOOP_OPTS -XX:NewRatio=12 -Xmx12288m -Xms10m -XX:MaxHeapFreeRatio=40 -XX:MinHeapFreeRatio=15 -XX:-UseGCOverheadLimit"
  fi
fi

export HADOOP_HEAPSIZE=2048

You can choose whether to use the Concurrent Collector or the New Parallel Collector for garbage collection, by passing -XX:+UseParNewGC or -XX:+UseConcMarkSweepGC in the HADOOP_OPTS lines above, and you can tune the garbage collection overhead limit by setting -XX:-UseGCOverheadLimit. To enable the garbage collection overhead limit, remove the setting or change it to -XX:+UseGCOverheadLimit.

Configuration for WebHCat

If you want to use WebHCat, you need to set the PYTHON_CMD variable in /etc/default/hive-webhcat-server after installing Hive; for example: 
export PYTHON_CMD=/usr/bin/python

Transaction (ACID) Support in Hive

The CDH distribution of Hive does not support transactions (HIVE-5317). Currently, transaction support in Hive is an experimental feature that only works with the ORC file format. Cloudera recommends using the Parquet file format, which works across many tools. Merge updates in Hive tables using existing functionality, including statements such as INSERT, INSERT OVERWRITE, and CREATE TABLE AS SELECT.