[jira] [Commented] (BOOKKEEPER-215) Deadlock occurs under high load

["Flavio Junqueira (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/BOOKKEEPER-215?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13268952#comment-13268952 ] 

Flavio Junqueira commented on BOOKKEEPER-215:
---------------------------------------------

It really feels like we have three issues here: the hedwig deadlock, the changes to recovery, deadlock detection. In this jira, it sounds like we only need to solve the first. The other two we should address in different jiras.

On the changes to recovery to not acquire/release permits, I don't really like the conditional acquire/permit, and I was thinking if we could remove it by just acquiring and releasing in different places. For adds, we could acquire the permits before doAsyncAddEntry, while for the release part, we may need a different callback in PendingAddOp. What do you think, Sijie? 
                
> Deadlock occurs under high load
> -------------------------------
>
>                 Key: BOOKKEEPER-215
>                 URL: https://issues.apache.org/jira/browse/BOOKKEEPER-215
>             Project: Bookkeeper
>          Issue Type: Bug
>          Components: hedwig-server
>    Affects Versions: 4.1.0
>            Reporter: Aniruddha
>            Assignee: Sijie Guo
>            Priority: Critical
>             Fix For: 4.1.0
>
>         Attachments: BK-215-check-deadlock.patch, BK-215.patch, BK-215.patch_v2, BK-215.patch_v3, DeadlockCheckOrderedSafeExecutor.java, hedwig_ts.log
>
>
> LedgerHandle uses a Semaphore(opCounterSem) with a default value of 5000 permits to implement throttling for outstanding requests. This is causing a deadlock under high load. What I've observed is the following - There are a fixed number of threads created by OrderedSafeExecutor(mainWorkerPool in BookKeeper) and this is used to execute operations by PerChannelBookieClient. Under high load, the bookies are not able to satisfy requests at the rate at which they are being generated. This exhausts all permits in the Semaphore and any further operations block on lh.opCounterSem.acquire(). In this scenario, if the connection to the bookies is shut down, channelDisconnected in PerChannelBookieClient tries to error out all outstanding entries. The errorOutReadKey and errorOutAddKey functions enqueue these operations in the same mainWorkerPool, all threads in which are blocked on acquire. So, handleBookieFailure is never executed and the server stops responding. 
> Blocking operations in a fixed size thread pool doesn't sound quite right. Temporarily, I fixed this by having another ExecutorService for every PerChannelBookieClient and queuing the operations from the errorOut* functions in it, but this is just a quick fix. I feel that the server shouldn't rely on LedgerHandle to throttle connections, but do this itself. Any other ideas on how to fix this? I'd be happy to contribute a patch. 

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira