[GitHub] curator pull request: CURATOR-157 Avoid stack traces on close

[madrob <gi...@git.apache.org>]

Github user madrob commented on the pull request:

    https://github.com/apache/curator/pull/51#issuecomment-73259604
  
    Looks like I neglected to respond to this for a while. Here is why I think the logic is faulty.
    
    T2: `processResult()` method entry
    T2: `synchronized (backgroundTaskMonitor)` acquire lock
    T2: `if (state.get().equals(State.CLOSED)) { }` evaluates false
    T1: `close()` method entry
    T1: `if ( state.compareAndSet(State.STARTED, State.CLOSED) )` evaluates true
    T1: `listeners.clear()`
    T1:  `client.getConnectionStateListenable().removeListener(connectionStateListener)`
    T1 suspends waiting for the lock
    T2: `processBackgroundResult(event)` gets called on a closed connection
    
    I think the solution is to put all of the `close()` method into the `synchronized` block, but that is not a super appealing answer. Maybe it will be fine though.
    
    The other concern is that now we can only process a single background event at a time, which seems like it could be a pretty high price to pay.


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