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metainfo.xml is a declarative definition of an Ambari managed service describing its content. It is the most critical file for any service definition. This section describes various key sub-sections within a metainfo.xml file.

Structure

Non-mandatory fields are described in italics.

The fields to describe a service are as follows:

  • name: the name of the service. A name has to be unique among all the services that are included in the stack definition containing the service.

  • displayName: the display name of the service

  • version: the version of the service. name and version together uniquely identify a service. Usually, the version is the version of the service binary itself.

  • components: the list of component that the service is comprised of

  • osSpecifics: OS specific package information for the service

  • commandScript: service level commands may also be defined. The command is executed on a component instance that is a client

  • comment: a short description describing the service

  • requiredServices: what other services that should be present on the cluster

  • configuration-dependencies: configuration files that are expected by the service (config files owned by other services are specified in this list)

service/components - A service contains several components. The fields associated with a component are:

  • name: name of the component

  • category: type of the component - MASTER, SLAVE, and CLIENT

  • commandScript: application wide commands may also be defined. The command is executed on a component instance that is a client

  • cardinality: allowed/expected number of instances

  • versionAdvertised: does the component advertise its version - used during rolling/express upgrade

  • timelineAppid: the default category used to store generated metrics data

  • dependencies: the list of components that this component depends on

  • customCommands: a set of custom commands associated with the component in addition to standard commands

service/osSpecifics - OS specific package names (rpm or deb packages)

  • osFamily: the os family for which the package is applicable

  • packages: list of packages that are needed to deploy the service

  • package/name: name of the package (will be used by the yum/zypper/apt commands)

 

service/commandScript - the script that implements service check (see service/component/customCommand below)
service/component/commandScript - the script that implements components specific default commands (see service/component/customCommand below)

service/component/customCommand - custom commands can be added to components.
  • name: name of the custom command
  • commandScript: the details of the script that implements the custom command
  • commandScript/script: the relative path to the script
  • commandScript/scriptType: the type of the script, currently only supported type is PYTHON
  • commandScript/timeout: custom timeout for the command - this supersedes ambari default 

service/component/configFiles - list of config files to be available when client config is to be downloaded (used to configure service clients that are not managed by Ambari)

  • type: the type of file to be generated, xml or env sh, yaml, etc
  • fileName: name of the generated file
  • dictionary: data dictionary that contains the config properties (relevant to how ambari manages config bags internally)

Sample metainfo.xml

<metainfo>
  <schemaVersion>2.0</schemaVersion>
  <services>
    <service>
      <name>HBASE</name>
      <displayName>HBase</displayName>
      <comment>Non-relational distributed database and centralized service for configuration management &amp;
 synchronization
      </comment>
      <version>0.96.0.2.0</version>
      <components>
        <component>
          <name>HBASE_MASTER</name>
          <displayName>HBase Master</displayName>
          <category>MASTER</category>
          <cardinality>1+</cardinality>
          <versionAdvertised>true</versionAdvertised>
          <timelineAppid>HBASE</timelineAppid>
          <dependencies>
            <dependency>
              <name>HDFS/HDFS_CLIENT</name>
              <scope>host</scope>
              <auto-deploy>
                <enabled>true</enabled>
              </auto-deploy>
            </dependency>
            <dependency>
              <name>ZOOKEEPER/ZOOKEEPER_SERVER</name>
              <scope>cluster</scope>
              <auto-deploy>
                <enabled>true</enabled>
                <co-locate>HBASE/HBASE_MASTER</co-locate>
              </auto-deploy>
            </dependency>
          </dependencies>
          <commandScript>
            <script>scripts/hbase_master.py</script>
            <scriptType>PYTHON</scriptType>
            <timeout>1200</timeout>
          </commandScript>
          <customCommands>
            <customCommand>
              <name>DECOMMISSION</name>
              <commandScript>
                <script>scripts/hbase_master.py</script>
                <scriptType>PYTHON</scriptType>
                <timeout>600</timeout>
              </commandScript>
            </customCommand>
          </customCommands>
        </component>

        <component>
          <name>HBASE_REGIONSERVER</name>
          <displayName>RegionServer</displayName>
          <category>SLAVE</category>
          <cardinality>1+</cardinality>
          <versionAdvertised>true</versionAdvertised>
          <timelineAppid>HBASE</timelineAppid>
          <commandScript>
            <script>scripts/hbase_regionserver.py</script>
            <scriptType>PYTHON</scriptType>
          </commandScript>
        </component>

        <component>
          <name>HBASE_CLIENT</name>
          <displayName>HBase Client</displayName>
          <category>CLIENT</category>
          <cardinality>1+</cardinality>
          <versionAdvertised>true</versionAdvertised>
          <commandScript>
            <script>scripts/hbase_client.py</script>
            <scriptType>PYTHON</scriptType>
          </commandScript>
          <configFiles>
            <configFile>
              <type>xml</type>
              <fileName>hbase-site.xml</fileName>
              <dictionaryName>hbase-site</dictionaryName>
            </configFile>
            <configFile>
              <type>env</type>
              <fileName>hbase-env.sh</fileName>
              <dictionaryName>hbase-env</dictionaryName>
            </configFile>
          </configFiles>
        </component>
      </components>

      <osSpecifics>
        <osSpecific>
          <osFamily>any</osFamily>
          <packages>
            <package>
              <name>hbase</name>
            </package>
          </packages>
        </osSpecific>
      </osSpecifics>

      <commandScript>
        <script>scripts/service_check.py</script>
        <scriptType>PYTHON</scriptType>
        <timeout>300</timeout>
      </commandScript>
      
      <requiredServices>
        <service>ZOOKEEPER</service>
        <service>HDFS</service>
      </requiredServices>

      <configuration-dependencies>
        <config-type>core-site</config-type>
        <config-type>hbase-site</config-type>
        <config-type>ranger-hbase-policymgr-ssl</config-type>
        <config-type>ranger-hbase-security</config-type>
      </configuration-dependencies>

    </service>
  </services>
</metainfo>
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