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Posted to common-issues@hadoop.apache.org by "CR Hota (JIRA)" <ji...@apache.org> on 2019/08/16 20:12:00 UTC
[jira] [Commented] (HADOOP-16268) Allow custom wrapped exception to
be thrown by server if RPC call queue is filled up
[ https://issues.apache.org/jira/browse/HADOOP-16268?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16909366#comment-16909366 ]
CR Hota commented on HADOOP-16268:
----------------------------------
[~xkrogen] Thanks for the review. Below is a little explanation of the change.
The idea here is to back off even if {{FairCallQueue}} is not configured (FairCallQueue in the context of router doesn't help much, as fairness in routers has a separate context as mentioned in HDFS-14090). So irrespective of actual queue implementation, if a queue is full call manager should throw {{StandbyException}} instead {{RetriableException}}. In case {{FairCallQueue}} is not enabled, the default {{LinkedBlockingQueue}} is used, which will throw an {{IllegalStateException}} when full and this exception also gets handled by {{throwBackoff}} logic. Let me know your thoughts.
[~jojochuang] [~elgoiri] [~brahmareddy] FYI ..
> Allow custom wrapped exception to be thrown by server if RPC call queue is filled up
> ------------------------------------------------------------------------------------
>
> Key: HADOOP-16268
> URL: https://issues.apache.org/jira/browse/HADOOP-16268
> Project: Hadoop Common
> Issue Type: Improvement
> Reporter: CR Hota
> Assignee: CR Hota
> Priority: Major
> Attachments: HADOOP-16268.001.patch
>
>
> In the current implementation of callqueue manager, "CallQueueOverflowException" exceptions are always wrapping "RetriableException". Through configs servers should be allowed to throw custom exceptions based on new use cases.
> In CallQueueManager.java for backoff the below is done
> {code:java}
> // ideally this behavior should be controllable too.
> private void throwBackoff() throws IllegalStateException {
> throw CallQueueOverflowException.DISCONNECT;
> }
> {code}
> Since CallQueueOverflowException only wraps RetriableException clients would end up hitting the same server for retries. In use cases that router supports these overflowed requests could be handled by another router that shares the same state thus distributing load across a cluster of routers better. In the absence of any custom exception, current behavior should be supported.
> In CallQueueOverflowException class a new Standby exception wrap should be created. Something like the below
> {code:java}
> static final CallQueueOverflowException KEEPALIVE =
> new CallQueueOverflowException(
> new RetriableException(TOO_BUSY),
> RpcStatusProto.ERROR);
> static final CallQueueOverflowException DISCONNECT =
> new CallQueueOverflowException(
> new RetriableException(TOO_BUSY + " - disconnecting"),
> RpcStatusProto.FATAL);
> static final CallQueueOverflowException DISCONNECT2 =
> new CallQueueOverflowException(
> new StandbyException(TOO_BUSY + " - disconnecting"),
> RpcStatusProto.FATAL);
> {code}
>
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