Re: [Sqlrelay-discussion] One more fault tolerance patch

[David M. <dav...@fi...>]

Actually, now that I look at it, the only other semaphore that could be 
a problem is 8, and I already did the same thing in the scaler to reset 
that one.  Yay!

On 06/29/2011 01:14 PM, David Muse wrote:
> Yeah, this is definitely an issue.  I wonder if the same issue exists 
> with other semaphores, depending on exactly where sqlr-connection exits.
>
> I think it would be ok just to reset the semaphore to 0 though, no 
> need to check its value first.
>
> On 06/29/2011 10:17 AM, Renat Sabitov wrote:
>> Hi David,
>>
>> I am continue testing and generating ideas :)
>>
>> If sqlr-connection is killed between signalListenerToRead() and 
>> waitForListenerToFinishReading(), sem(3) starts growing above one. 
>> This consequently breaks listener-connection communication and leads 
>> to hanging listener processes under high load.
>>
>> The patch changes wait points for sem(3) and sem(2) so the values of 
>> this semaphores is set to 0 after wait() completed. Since we can not 
>> use "WithUndo" on inter-process communication semaphores, I suppose 
>> it is a good idea in general to check the state and revert it to normal.
>>
>>
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