[AMBARI-2819] Extending Stack definition to remove duplication in stack metadata info.

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Component/s: ambari-server
• Assignee: Siddharth Wagle
• Reporter: Siddharth Wagle
• Created: 06/Aug/13 17:13
• Updated: 20/Jan/14 19:53
• Resolved: 23/Sep/13 18:47

Description

The idea is to allow extending a stack definition and overriding some of its values.

Current stack definition structure of files and directories:

|_ stacks
   |_ <dist_name>
      |_ <version_number>
         metainfo.xml
         |_ repos
             repoinfo.xml
         |_ services
            |_ <service_name>
               metainfo.xml
               |_ configuration
                  configuration files

We introduce extends element at the top level (stack version level) that links to the parent stack definition for this stack version.

Rules of extension:
1. All of the parent stack services are automatically a part of the child stack unless explicitly excluded.
2. Only one parent stack can be extended by the child stack.
3. <stacks>.<dist_name>.<repos>.repoinfo.xml, will not be overridden
4. All service configurations unless explicitly excluded are a part of the child service definition.

1. Extending stack definition

File: <stacks>.<dist_name>.<version_number>.metainfo.xml
E.g.: /stacks/HDP/1.3.1/metainfo.xml

<metainfo>
    <versions>
        <upgrade>1.2.0</upgrade>
    </versions>
    <active>true</active>
    <extends>1.3.0</extends>
</metainfo>

2. Extending service definition

<stacks>.<dist_name>.<version_number>.<service_name>.metainfo.xml
E.g.: /stacks/HDP/1.2.1/services/HDFS/metainfo.xml

<metainfo>
    <user>root</user>
    <comment>Apache Hadoop Distributed File System</comment>
    <version>1.1.2</version>
    <deleted>false<deleted>
</metainfo>

2.1 Extending component definition

Components can be added or deleted from the stack.

<component>
    <name>YARN_CLIENT</name>
    <category>CLIENT</category>
    <deleted>true</deleted>
</component>

3. Extending service configurations

File: <stacks>.<dist_name>.<version_number>.<service_name>.<configuration>.configuration_file
E.g.: /stacks/HDP/1.3.1/services/HDFS/configuration/hdfs-site.xml

<configuration>
  <property>
      <name>dfs.name.dir</name>
      <deleted>true</deleted>
  </property>
</configuration>

Notes:
The same property can disappear and reappear in an extension graph.

1.3.0 ----------------> 1.3.1 ----------------> 1.3.2 ----------------> 1.3.5
a = b                   a = c                                           a = c

Issue Links

• is related to: AMBARI-2714 Ability to dynamically add services to a stack.
• is related to: AMBARI-4358 Add stack extension support for pluggable services