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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (THRIFT-3891) TNonblockingServer configured with more than one IO threads does not always return from serve() upon stop()
Date Sun, 19 Feb 2017 04:20:44 GMT

    [ https://issues.apache.org/jira/browse/THRIFT-3891?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15873463#comment-15873463
] 

ASF GitHub Bot commented on THRIFT-3891:
----------------------------------------

Github user jeking3 commented on a diff in the pull request:

    https://github.com/apache/thrift/pull/1196#discussion_r101908414
  
    --- Diff: lib/cpp/src/thrift/server/TNonblockingServer.cpp ---
    @@ -820,9 +821,11 @@ void TNonblockingServer::TConnection::setFlags(short eventFlags)
{
      * Closes a connection
      */
     void TNonblockingServer::TConnection::close() {
    -  // Delete the registered libevent
    -  if (event_del(&event_) == -1) {
    -    GlobalOutput.perror("TConnection::close() event_del", THRIFT_GET_SOCKET_ERROR);
    +  if (eventFlags_) {
    +    if (event_del(&event_) == -1) {
    +      GlobalOutput("TConnection::close event_del");
    --- End diff --
    
    Sorry I copied this from another location and it must have been using GlobalOutput.  I
will fix this.


> TNonblockingServer configured with more than one IO threads does not always return from
serve() upon stop()
> -----------------------------------------------------------------------------------------------------------
>
>                 Key: THRIFT-3891
>                 URL: https://issues.apache.org/jira/browse/THRIFT-3891
>             Project: Thrift
>          Issue Type: Bug
>          Components: C++ - Library
>    Affects Versions: 0.9.3
>            Reporter: Buğra Gedik
>            Assignee: James E. King, III
>            Priority: Minor
>         Attachments: patch.diff
>
>
> Using {{TNonblockingServer}}, when the number of IO threads is > 1, there is race
condition in which {{stop()}} does not properly unblock {{serve()}}. 
> The problem manifests itself when {{stop()}} is called (obviously from a different thread)
soon after {{serve()}}. 
> The core issue is that, {{event_base_loopbreak()}} is called within the {{stop()}} sequence
without checking whether the IO thread has actually entered its event loop. The documentation
of {{event_base_loopbreak()}} says (http://www.wangafu.net/~nickm/libevent-book/Ref3_eventloop.html)
> {quote}
> Note also that event_base_loopexit(base,NULL) and event_base_loopbreak(base) act differently
when no event loop is running: loopexit schedules the next instance of the event loop to stop
right after the next round of callbacks are run (as if it had been invoked with EVLOOP_ONCE)
whereas loopbreak only stops a currently running loop, and has no effect if the event loop
isn’t running.
> {quote}
> Attached is a patch (against the released 0.9.3 version of the codebase).



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