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Design details and discussion for KNOX-88 

 

Definition

 

Knox HA is a set of routines for transparent work with Hadoop service that stands in HA mode.

 

Purpose of Knox HA service

 

  1. Automatic failover. (Example: switch request from not responding name-node to active name-node.)
  2. Pluggable support of failover strategies.
  3. Daemon-service for regular ping of Hadoop service state (Performance optimization to keeping actual state of service).

 

 

Code Block
languagexml
titleTopology
linenumberstrue
<topology>
  <gateway>
    ...
    <provider>
      <role>ha</role>
      <name>HAProvider</name>
      <enabled>true</enabled>
      <param>
        <name>webhdfs.ha</name>
        <value>failover_strategy=BaseStrategy;retryCount=3;timeoutInterval=5000;enabled=5000<true</value>
      </param>
    </provider>    
    ...
  <gateway>
  ...
  <service>
    <role>WEBHDFS</role>
    <url>machine1.example.com:50070</url>
    <url>machine2.example.com:50070</url>
  </service>
  ...
<service>
    <role>NAMENODE</role>
    <url>machine1.example.com:50070</url>
    <url>machine2.example.com:50070</url>
</service>
...
</topology>

Example UML

...