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From tillrohrmann <...@git.apache.org>
Subject [GitHub] flink pull request: [FLINK-2354] Add job graph and checkpoint reco...
Date Mon, 05 Oct 2015 14:35:20 GMT
Github user tillrohrmann commented on a diff in the pull request:

    https://github.com/apache/flink/pull/1153#discussion_r41150514
  
    --- Diff: flink-runtime/src/main/java/org/apache/flink/runtime/leaderelection/LeaderElectionService.java
---
    @@ -67,4 +67,20 @@
     	 * @return true if the associated {@link LeaderContender} is the leader, otherwise false
     	 */
     	boolean hasLeadership();
    +
    +	/**
    +	 * [EXPERIMENTAL] Returns <code>true</code> if the {@link LeaderContender}
is leader. A call
    +	 * to this method might block.
    +	 *
    +	 * <p>This forces a synchronous check at the respective state backend. It is possible
    +	 * that is does not reflect the current state at the {@link LeaderContender}, which
is notified
    +	 * asynchronously. Therefore it is possible that {@link #hasLeadership()} and {@link
    +	 * #syncHasLeadership()} have different return values.
    +	 *
    +	 * @TODO @tillrohrmann Is it OK to collapse this with {@link #hasLeadership()}?
    +	 *
    +	 * @return true if the associated {@link LeaderContender} is the leader, otherwise false
    +	 */
    +	boolean syncHasLeadership();
    --- End diff --
    
    Hmm, but the Javadoc suggests a wrong guarantee which does not always hold true. The thing
is that we don't really know what are the chances to observe a wrong leadership and to what
extent this method decreases them. 


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