[jira] [Created] (FLINK-1489) Failing JobManager due to blocking calls in Execution.scheduleOrUpdateConsumers

["Till Rohrmann (JIRA)" <ji...@apache.org>]

Till Rohrmann created FLINK-1489:
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             Summary: Failing JobManager due to blocking calls in Execution.scheduleOrUpdateConsumers
                 Key: FLINK-1489
                 URL: https://issues.apache.org/jira/browse/FLINK-1489
             Project: Flink
          Issue Type: Bug
            Reporter: Till Rohrmann
            Assignee: Till Rohrmann


[~Zentol] reported that the JobManager failed to execute his python job. The reason is that the the JobManager executes blocking calls in the actor thread in the method {{Execution.sendUpdateTaskRpcCall}} as a result to receiving a {{ScheduleOrUpdateConsumers}} message. 

Every TaskManager possibly sends a {{ScheduleOrUpdateConsumers}} to the JobManager to notify the consumers about available data. The JobManager then sends to each TaskManager the respective update call {{Execution.sendUpdateTaskRpcCall}}. By blocking the actor thread, we effectively execute the update calls sequentially. Due to the ever accumulating delay, some of the initial timeouts on the TaskManager side in {{IntermediateResultParititon.scheduleOrUpdateConsumers}} fail. As a result the execution of the respective Tasks fails.

A solution would be to make the call non-blocking.

A general caveat for actor programming is: We should never block the actor thread, otherwise we seriously jeopardize the scalability of the system. Or even worse, the system simply fails.



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