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Provider configuration example

Enables or disables HA Provider and binds strategy and provider together. Alias contains list of Hadoop services (name-nodes in our case: active and standby) grouped into one entity.

<topology>
  <gateway>
    ...
    <provider>
    <role>ha</role>
    <name>HAProvider</name>
    <param>
        <name>webhdfs.ha</name>
        <value>failover_strategy=BaseStrategy;retryCount=3;timeoutInterval=5000;enabled=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>

• failover_strategy – indicates how to define active service and contains some configuration parameters. Default value is BaseStrategy. BaseStrategy for failover has following parameters:
• retryCount – indicates how many times knox will ping name-node before  knox decides that namenode is down.
• timeoutInterval – interval for connection timeout. 
• enabled – indicates whether  HAProvider  is active or not for service.

Example UML

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participant "Deployment\nFactory\n(df)" as df

Example Code Block

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Please look at the WebHDFS HA section http://knox.apache.org/books/knox-0-5-0/knox-0-5-0.html#WebHDFS