Configuring Druid to use a Kerberized Hadoop as Deep Storage

Hadoop Setup

Following are the configurations files required to be copied over to Druid conf folders:

1. For HDFS as a deep storage, hdfs-site.xml, core-site.xml
2. For ingestion, mapred-site.xml, yarn-site.xml

HDFS Folders and permissions

1. Choose any folder name for the druid deep storage, for example 'druid'

2. Create the folder in hdfs under the required parent folder. For example, hdfs dfs -mkdir /druid OR hdfs dfs -mkdir /apps/druid

3. Give druid processes appropriate permissions for the druid processes to access this folder. This would ensure that druid is able to create necessary folders like data and indexing_log in HDFS. For example, if druid processes run as user 'root', then

   hdfs dfs -chown root:root /apps/druid

   OR

   hdfs dfs -chmod 777 /apps/druid

Druid creates necessary sub-folders to store data and index under this newly created folder.

Druid Setup

Edit common.runtime.properties at conf/druid/_common/common.runtime.properties to include the HDFS properties. Folders used for the location are same as the ones used for example above.

common_runtime_properties

# Deep storage
#
# For HDFS:
 druid.storage.type=hdfs
 druid.storage.storageDirectory=/druid/segments
# OR
# druid.storage.storageDirectory=/apps/druid/segments

#
# Indexing service logs
#

# For HDFS:
druid.indexer.logs.type=hdfs
druid.indexer.logs.directory=/druid/indexing-logs
# OR
# druid.storage.storageDirectory=/apps/druid/indexing-logs

Note: Comment out Local storage and S3 Storage parameters in the file

Also include hdfs-storage core extension to conf/druid/_common/common.runtime.

#
# Extensions
#

druid.extensions.directory=dist/druid/extensions
druid.extensions.hadoopDependenciesDir=dist/druid/hadoop-dependencies
druid.extensions.loadList=["druid-parser-route", "mysql-metadata-storage", "druid-hdfs-storage", "druid-kerberos"]

Hadoop Jars

Ensure that Druid has necessary jars to support the Hadoop version.

Find the hadoop version using command, hadoop version

In case there are other softwares used with hadoop, like WanDisco, ensure that

1. the necessary libraries are available
2. add the requisite extensions to druid.extensions.loadlist in conf/druid/_common/common.runtime.properties

Kerberos setup

Create a headless keytab which would have access to the druid data and index.

Edit conf/druid/_common/common.runtime.properties and add the following properties:

druid.hadoop.security.kerberos.principal
druid.hadoop.security.kerberos.keytab

For example

druid.hadoop.security.kerberos.principal=hdfs-test@EXAMPLE.IO
druid.hadoop.security.kerberos.keytab=/etc/security/keytabs/hdfs.headless.keytab

Restart Druid Services

With the above changes, restart Druid. This would ensure that Druid works with Kerberized Hadoop