Github user mxm commented on the issue:
https://github.com/apache/flink/pull/2571
Thanks for the feedback, @beyond1920 and @KurtYoung.
You're right, the changes don't allow slots to be released by a
TaskExecutor. We can change that by explicitly reporting to the RM if a slot
becomes free. This may also decrease latency in case a tasks finishes and new
ones are waiting to be deployed.
>b. When we handleSlotRequestFailedAtTaskManager, we will make this slot
free again. If the slot is occupied by some other task now, we will
continuously failed for all allocation on this slot. ( this can be fixed by 3)
How can that happen? The slot will not appear free while it is allocated at
the TaskExecutor. When allocation fails, it is marked as free and then the
request is retried immediately. It must succeed eventually if the initial
decision to allocate the slot was correct. However, we need to explicitly check
if a TaskExecutor has deregistered, to make sure old TaskExecutors don't send
failures which triggers slot allocation of already removed slots (due to
TaskExecutor deregistration). That should be fix with this PR.
> 1. We can remove the update status part entirely, since it can only do
new slot registration now, we can just move it to the task executor first
registration.
Very good suggestion. Let's move the initial registration and
reconciliation of slots to the registration message.
To wrap up, let's change the following:
1. Move the slot registration and allocation report to the registration of
the TaskExecutor
2. Let the TaskExecutor immediately notify the ResourceManager once a slot
becomes free
3. Change the fencing in handleSlotRequestFailedAtTaskManager to protect
against TaskExecutors which are not registered anymore.
Let me know if that would work for you.
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