Writing metainfo.xml

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

Non-mandatory fields are described in italics.

The top level fields to describe a service are as follows:

Feild	What is it used for	Sample Values
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.	HDFS
displayName	the display name of the service	HDFS
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.	2.1.0.2.0
components	the list of component that the service is comprised of	`<check out HDFS metainfo>`
osSpecifics	OS specific package information for the service	`<check out HDFS metainfo>`
commandScript	service level commands may also be defined. The command is executed on a component instance that is a client	`<check out HDFS metainfo>`
comment	a short description describing the service	Apache Hadoop Distributed File System
requiredServices	what other services that should be present on the cluster	`<check out HDFS metainfo>`
configuration-dependencies	configuration files that are expected by the service (config files owned by other services are specified in this list)	`<check out HDFS metainfo>`
restartRequiredAfterRackChange	Restart Required After Rack Change	true / false
configuration-dir	Use this to specify a different config directory if not ‘configuration’	-

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

Feild	What is it used for	Sample Values
name	name of the component	HDFS
displayName	display name of the component.	HDFS
category	type of the component - MASTER, SLAVE, and CLIENT	2.1.0.2.0
commandScript	application wide commands may also be defined. The command is executed on a component instance that is a client	`<check out HDFS metainfo>`
cardinality	allowed/expected number of instances	For example, 1-2 for MASTER, 1+ for Slave
reassignAllowed	whether the component can be reassigned / moved to a different host.	true / false
versionAdvertised	does the component advertise its version - used during rolling/express upgrade	Apache Hadoop Distributed File System
timelineAppid	This will be the component name under which the metrics from this component will be collected.	`<check out HDFS metainfo>`
dependencies	the list of components that this component depends on	`<check out HDFS metainfo>`
customCommands	a set of custom commands associated with the component in addition to standard commands.	RESTART_LLAP (Check out HIVE metainfo)

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

Feild	What is it used for	Sample Values
osFamily	the os family for which the package is applicable	any => all amazon2015,redhat6,debian7,ubuntu12,ubuntu14,ubuntu16
packages	list of packages that are needed to deploy the service	`<check out HDFS metainfo>`
package/name	name of the package (will be used by the yum/zypper/apt commands)	Eg hadoop-lzo.

service/commandScript - the script that implements service check

Feild	What is it used for
script	the relative path to the script
scriptType	the type of the script, currently only supported type is PYTHON
timeout	custom timeout for the command - this supersedes ambari default

sample values:

<commandScript>
  <script>scripts/service_check.py</script>
  <scriptType>PYTHON</scriptType>
  <timeout>300</timeout>
</commandScript>

service/component/dependencies/dependency

Feild	What is it used for
name	name of the component it depends on
scope	cluster / host. specifies whether the dependent component should be present in the same cluster or the same host.
auto-deploy	custom timeout for the command - this supersedes ambari default
conditions	Conditions in which this dependency exists. For example, the presence of a property in a config.

sample values:

<dependency>
  <name>HDFS/ZKFC</name>
  <scope>cluster</scope>
  <auto-deploy>
    <enabled>false</enabled>
  </auto-deploy>
  <conditions>
    <condition xsi:type="propertyExists">
      <configType>hdfs-site</configType>
      <property>dfs.nameservices</property>
    </condition>
  </conditions>
</dependency>

service/component/commandScript - the script that implements components specific default commands (Similar to service/commandScript )

service/component/logs - provides log search integration.

Feild	What is it used for
logId	logid of the component
primary	primary log id or not.

sample values:

<log>
  <logId>hdfs_namenode</logId>
  <primary>true</primary>
</log>

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>