Analytics node configuration

Steps to configure analytic Hadoop nodes.

Important configuration changes, excluding those related to the job tracker, are:

Advanced users can also configure DataStax Enterprise to run jobs remotely.

DataStax Enterprise turns off virtual nodes (vnodes) by default. DataStax does not recommend turning on vnodes for Hadoop or Solr nodes, but you can use vnodes for any Cassandra-only cluster, or a Cassandra-only data center in a mixed Hadoop/Solr/Cassandra deployment. If you have enabled virtual nodes on Hadoop nodes, disable virtual nodes before using the cluster.

Setting the replication factor

The default replication for the HiveMetaStore, cfs, and cfs_archive system keyspaces is 1. A replication factor of 1 using the default data center Analytics is configured for development and testing of a single node, not for a production environment. For production clusters, increase the replication factor to at least 2. The higher replication factor ensures resilience to single-node failures. For example:

ALTER KEYSPACE cfs
  WITH REPLICATION = {'class' : 'NetworkTopologyStrategy', 'dc1' : 3};

Configuring the verbosity of log messages

To adjust the verbosity of log messages for Hadoop map/reduce tasks, add the following settings to the log4j.properties file on each analytic node:

log4j.logger.org.apache.hadoop.mapred=WARN 
log4j.logger.org.apache.hadoop.filecache=WARN

Default Hadoop log4j-server.properties locations:

Installer-Services and Package installations: /etc/dse/hadoop/
Installer-No Services and Tarball installations: install_location/resources/hadoop/conf/

Connecting to non-standard Cassandra native port

If the Cassandra native port was changed to a port other than the default port 9042, you must change the cassandra.input.native.port configuration setting for Hive and Hadoop to use the non-default port. The following examples change the Cassandra native port protocol connections to use port 9999.

Inside the Hive shell, set the port after starting DSE Hive:
```
$ dse hive
hive> set cassandra.input.native.port=9999; 
```

General Hive, add cassandra.input.native.port to the hive-site.xml file:

<property> 
    <name>cassandra.input.native.port</name>
    <value>9999</value> 
</property>

For Hadoop, add cassandra.input.native.port to the core-site.xml file:

<property> 
    <name>cassandra.input.native.port</name> 
    <value>9999</value> 
</property>

Configuration for running jobs on a remote cluster

This information is intended for advanced users.

Procedure

To connect to external addresses:

Make sure that the hostname resolution works properly on the localhost for the remote cluster nodes.
Copy the dse-core-default.xml and dse-mapred-default.xml files from any working remote cluster node to your local Hadoop conf directory.
Run the job using dse hadoop.
If you need to override the JT location or if DataStax Enterprise cannot automatically detect the JT location, before running the job, define the HADOOP_JT environment variable:
```
$ export HADOOP_JT=jobtracker host:jobtracker port dse hadoop jar ....
```
If you need to connect to many different remote clusters from the same host:
1. Before starting the job, copy the remote Hadoop conf directories fully to the local node (into different locations).
2. Select the appropriate location by defining HADOOP_CONF_DIR.