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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-4348) Implement slot allocation protocol with TaskExecutor
Date Thu, 06 Oct 2016 13:22:20 GMT

    [ https://issues.apache.org/jira/browse/FLINK-4348?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15551911#comment-15551911

ASF GitHub Bot commented on FLINK-4348:

Github user mxm commented on the issue:

    Rebased to latest `flip-6`.

> Implement slot allocation protocol with TaskExecutor
> ----------------------------------------------------
>                 Key: FLINK-4348
>                 URL: https://issues.apache.org/jira/browse/FLINK-4348
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Cluster Management
>            Reporter: Kurt Young
>            Assignee: Maximilian Michels
> When slotManager finds a proper slot in the free pool for a slot request,  slotManager
marks the slot as occupied, then tells the taskExecutor to give the slot to the specified
> when a slot request is sent to taskExecutor, it should contain following parameters:
AllocationID, JobID,  slotID, resourceManagerLeaderSessionID. 
> There exists 3 following possibilities of the response from taskExecutor, we will discuss
when each possibility happens and how to handle.
> 1. Ack request which means the taskExecutor gives the slot to the specified jobMaster
as expected.   
> 2. Decline request if the slot is already occupied by other AllocationID.  
> 3. Timeout which could caused by lost of request message or response message or slow
network transfer. 
> On the first occasion, ResourceManager need to do nothing. However, under the second
and third occasion, ResourceManager need to notify slotManager, slotManager will verify and
clear all the previous allocate information for this slot request firstly, then try to find
a proper slot for the slot request again. This may cause some duplicate allocation, e.g. the
slot request to TaskManager is successful but the response is lost somehow, so we may request
a slot in another TaskManager, this causes two slots assigned to one request, but it can be
taken care of by rejecting registration at JobMaster.
> There are still some question need to discuss in a step further.
> 1. Who send slotRequest to taskExecutor, SlotManager or ResourceManager? I think it's
better that SlotManager delegates the rpc call to ResourceManager when SlotManager need to
communicate with outside world.  ResourceManager know which taskExecutor to send the request
based on ResourceID. Besides this RPC call which used to request slot to taskExecutor should
not be a RpcMethod,  because we hope only SlotManager has permission to call the method, but
the other component, for example JobMaster and TaskExecutor, cannot call this method directly.
> 2. If JobMaster reject the slot offer from a TaskExecutor, the TaskExecutor should notify
the free slot to ResourceManager immediately, or wait for next heartbeat sync. The advantage
of first way is the resourceManager’s view could be updated faster. The advantage of second
way is save a RPC method in ResourceManager.
> 3. There are two communication type. First, the slot request could be sent as an ask
operation where the response is returned as a future. Second, resourceManager send the slot
request in fire and forget way, the response could be returned by an RPC call. I prefer the
first one because it is more simple and could save a RPC method in ResourceManager (for callback
in the second way).

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