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From srdo <...@git.apache.org>
Subject [GitHub] curator issue #215: CURATOR-106: Ensure background operations happen in the ...
Date Sat, 22 Apr 2017 17:08:26 GMT
Github user srdo commented on the issue:

    https://github.com/apache/curator/pull/215
  
    Hi @Randgalt. Just to make sure, you're talking about calls to BackgroundCallback.processResult,
right?
    
    I don't follow how this change causes those to be invoked from a different thread than
usual. The changed code is only hit if processBackgroundOperation is called with a null event
(isInitialExecution is true). As far as I can tell, the invocations that happen from the Zookeeper
callbacks always seem to pass a non-null event, and so don't hit the changed code. 
    
    I took a look at the call sites for BackgroundCallback.processResult, and the only way
I can see that this change has changed the calling thread is if CuratorFrameworkImpl.processBackgroundOperation
is called with a null parameter, and CuratorFrameworkImpl.performBackgroundOperation then
hits a ConnectionLossException, through checkBackgroundRetry -> sendToBackgroundCallback
-> BackgroundCallback.processResult. https://github.com/apache/curator/blob/master/curator-framework/src/main/java/org/apache/curator/framework/imps/CuratorFrameworkImpl.java#L857.
The other invocations of sendToBackgroundCallback (the only call site for BackgroundCallback.processResult
except for the wrapper in Backgrounding) only happen through a call to processBackgroundOperation
with a non-null event.
    
    I did a quick spot check using the BackgroundCallback in CuratorFrameworkBackground.testBasic.
Printing the thread executing BackgroundCallback.processResult before the change:
    The executing thread Thread[main-EventThread,5,main]
    
    after the change:
    The executing thread Thread[main-EventThread,5,main]


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