This document describes how to configure the services to be deployed on YARN

There are mainly three types of configurations:

Below describes the details for each type of configurations.

Configuration for custom service

Below is how a configuration object typically looks like:

"configuration" : {
    "properties" : {
        "yarn.service.am-restart.max-attempts" : 10  // config for the service AM
    },
    "env" : {                 // The environment variables to be exported when container gets launched
        "env1" : "val1"
    },
    "files" : [               // The list of configuration files to be mounted for the container
        {
            "type": "HADOOP_XML", // The format of the config file into which the "properties" are dumped
            "dest_file": "/etc/hadoop/conf/core-site.xml", // The location where the config file is mounted inside the container
            "properties" : {             // The list of key/value pairs to be dumped into the config file
                "fs.defaultFS" : "hdfs://myhdfs" // This property will be written into core-site.xml
            }
        },
        {
            "type": "HADOOP_XML",    // The format of the config file.
            "src_file" : ""hdfs://mycluster/tmp/conf/yarn-site.xml""  // The location of the source config file to be downloaded
            "dest_file": "/etc/hadoop/conf/yarn-site.xml",            // The location where the config file will be mounted inside the container/
            "properties" : {
                "yarn.resourcemanager.webapp.address" : "${COMPONENT_INSTANCE_NAME}.${SERVICE_NAME}.${USER}.${DOMAIN}"  // Merge into (or override existing property in) yarn-site.xml
            }
        }
    ]
}
  • properties: the configurations for service AM. Details below.
  • env : the environment variables to be exported when container gets launched.
  • files : The list of configuration files to be mounted inside the container.
    • type: The format of the config file(dest_file) to be mounted inside the container. If src_file is specified, it is also the format for both src_file and dest_file.
    • HADOOP_XML : the hadoop xml format. If src_file is specified, the file content will be read as parsed in hadoop xml format.
    • XML : the standard xml format
    • JSON : the standard JSON format
    • YAML : the YAML format
    • PROPERTIES : the java PROPERTIES format
    • TEMPLATE : the plain text format. If src_file is specified, the content of the src_file will be written into dest_file post constant substitution. If src_file is not specified, use content as the key in properties field, and the value will be the actual content to be written in the dest_file post constant substitution. E.g 
      {
    "type": "TEMPLATE"
    "dest_file": "/etc/conf/hello"
    "properties" : {
         "content" : "Hello world"
    }
}

      The string Hello world will be written into a file located at /etc/conf/hello inside the container.

    • src_file : [optional], the source location of the config file at a network accessible location such as hdfs.
    • The format of both src_file and dest_file are defined by type.
    • Currently, It only works with HADOOP_XML and TEMPLATE type.
    • The src_file will be downloaded by YARN NodeManager and be mounted inside the container as in the location specified by dest_file.
    • If any properties specified in the properties field, they are added into (or overwriting existing properties in) the src_file.
    • If src_file is not specified, only the properties in the properties field will be written into the dest_file file.
    • dest_file : the location where the config file is mounted inside the container. The file format is defined by type. dest_file can be an absolute path or a relative path. If it’s a relative path, the file will be located in the $PWD/conf directory (where $PWD is the container local directory which is mounted to all docker containers launched by YARN)
    • properties : The list of key/value pair configs to be written into the dest_file in the format as defined in type. If src_file is specified, these properties will be added into (or overwriting existing properties in) the src_file.

Configuration for YARN service AM

This section describes the configurations for configuring the YARN service AM.

These can be specified either in the cluster yarn-site.xml at the global level or in the properties field of the Configuration object as per service basis like below:

{
    "configuration" : {
        "properties" : {
            "yarn.service.am-restart.max-attempts" : 10
        }
    }
}

Above config make the service AM to be retried at max 10 times.

Available configurations:

Name Description
yarn.service.client-am.retry.max-wait-ms the max retry time in milliseconds for the service client to talk to the service AM. By default, it is set to 0, which means no retry
yarn.service.client-am.retry-interval-ms the retry interval in milliseconds for the service client to talk to the service AM. By default, it is 2000, i.e. 2 seconds
yarn.service.container-failure.retry.max the max number of retries for the container to be auto restarted if it fails. By default, it is set to -1, which means forever.
yarn.service.container-failure.retry-interval-ms the retry interval in milliseconds for the container to be restarted. By default, it is 30000, i.e. 30 seconds
yarn.service.am-restart.max-attempts the max number of attempts for the framework AM
yarn.service.am-resource.memory the memory size in GB for the framework AM. By default, it is set to 1024
yarn.service.queue the default queue to which the service will be submitted. By default, it is submitted to default queue
yarn.service.base.path the root location for the service artifacts on hdfs for a user. By default, it is under ${user_home_dir}/.yarn/
yarn.service.container-failure-per-component.threshold the max number of container failures for a given component before the AM exits.
yarn.service.node-blacklist.threshold Maximum number of container failures on a node before the node is blacklisted by the AM
yarn.service.failure-count-reset.window The interval in seconds when the yarn.service.container-failure-per-component.threshold and yarn.service.node-blacklist.threshold gets reset. By default, it is 21600, i.e. 6 hours
yarn.service.readiness-check-interval.seconds The interval in seconds between readiness checks. By default, it is 30 seconds
yarn.service.log.include-pattern The regex expression for including log files whose file name matches it when aggregating the logs after the application completes.
yarn.service.log.exclude-pattern The regex expression for excluding log files whose file name matches it when aggregating the logs after the application completes. If the log file name matches both include and exclude pattern, this file will be excluded.
yarn.service.rolling-log.include-pattern The regex expression for including log files whose file name matches it when aggregating the logs while app is running.
yarn.service.rolling-log.exclude-pattern The regex expression for excluding log files whose file name matches it when aggregating the logs while app is running. If the log file name matches both include and exclude pattern, this file will be excluded.
yarn.service.container-recovery.timeout.ms The timeout in milliseconds after which the service AM releases all the containers of previous attempt which are not yet recovered by the RM. By default, it is set to 120000, i.e. 2 minutes.

Constant variables for custom service

The service framework provides some constant variables for user to configure their services. These variables are either dynamically generated by the system or are static ones such as service name defined by the user. User can use these constants in their configurations to be dynamically substituted by the service AM.E.g.

{
    "type" : "HADOOP_XML",
    "dest_file" : "/etc/hadoop/hbase-site.xml",
    "properties" : {
        "hbase.regionserver.hostname": "${COMPONENT_INSTANCE_NAME}.${SERVICE_NAME}.${USER}.${DOMAIN}"
    }
}

Here, COMPONENT_INSTANCE_NAME and SERVICE_NAME are the constants to be substituted by the system.

Suppose the COMPONENT_INSTANCE_NAME is regionserver-0 and SERVICE_NAME is defined by user as hbase, user name is devuser and domain name is dev.test. Then, the config will be substituted by the service AM and written in the config file /etc/hadoop/hbase-site.xml inside the container as below:

<property>
  <name>hbase.regionserver.hostname</name>
  <value>regionserver-0.hbase.devuser.dev.test</value>
</property>

where regionserver-0 is the actual component instance name assigned by the system for this container.

Available constants:

Name Description
SERVICE_NAME name of the service defined by the user
USER user who submits the service. Note that user name which has “_” will be converted to use “-”, to conform with DNS hostname RFC format which doesn’t allow “_”, and all characters will be lowercased E.g. “Bob_dev” will be converted to “bob-dev”
DOMAIN the domain name for the cluster
COMPONENT_NAME the name for a given component
COMPONENT_INSTANCE_NAME the name for a given component instance (i.e. container)
COMPONENT_ID the monotonically increasing integer for a given component
CONTAINER_ID the YARN container Id for a given container
${COMPONENT_INSTANCE_NAME}_HOST the hostname for a component instance (i.e. container), e.g. REGIONSERVER-0_HOST will be substituted by the actual hostname of the component instance. Note all characters must be uppercase.
${COMPONENT_INSTANCE_NAME}_IP the ip for a component instance (i.e. container), e.g. REGIONSERVER-0_IP will be substituted by the actual IP address of the component instance. Note all characters must be uppercase.
CLUSTER_FS_URI the URI of the cluster hdfs