Re: objectsWithFetchSpecification freezes during a slow call

On 8 Aug 2013, at 19:21, Chuck Hill <[email protected]> wrote:

> Hi Mark,
> 
> It freezes for a while (10+ seconds) or it freezes forever?  

Forever.  No errors. It just doesn't progress past the fetch command. 

> Have you tried a "sudo jstack -F <process id> to see where it is frozen?  

Will do, but not right now.
(Waiting for my main course to arrive.)

> It does sound like a timeout thing, perhaps at the JDBC level.  

I think so too, but not sure how to fix/increase it. 

> Does CREATED_DATE have an index?  

No, and we will add one.
But the point is, it should not freeze if MySql takes a few second too long too respond. 

> CREATED_DATE, QUEUE_ITEM_PK would be the fastest.
> 
> Chuck
> 
> 
> On 2013-08-08, at 10:22 AM, Mark Gowdy wrote:
> 
>> Hi, 
>> 
>> Have been trying to track down the cause of a very strange problem we have been having.
>> 
>> Using the MySQLPlugIn in Wonder, if we do a fetch (or anything SQL related), and it takes a while for MySQL to respond, the instance freezes (it does not get past the objectsWithFetchSpecification line).
>> We originally thought it was something to do with the memory & tables becoming large, but now we are thinking it is a response time-out thing.
>> 
>> We can reproduce the problem quite easily now by specifying a sort ordering, we will give MySQL a bit of work to do (and slow down the response).
>> 
>> So, if we run the generated SQL directly in Sequel Pro:
>> 
>> (1) Including the slow field (CREATED_DATE)- Takes about 10 seconds for MySQL to return some values.
>> SELECT RTRIM(t0.CONFIG), t0.CREATED_DATE, t0.IDENTIFIER_1, t0.IDENTIFIER_2, t0.IDENTIFIER_3, t0.IDENTIFIER_4, t0.ITEM_DATE, t0.MODIFIED_DATE, t0.QUEUE_DETAILS_FK, t0.QUEUE_ITEM_PK, t0.QUEUE_TAG, t0.STATUS FROM queue_item t0 WHERE (t0.QUEUE_TAG = 'mb:nui:RENDER_MEDIA' AND (t0.ITEM_DATE < '2013-08-08 16:46:17 Etc/GMT' OR t0.ITEM_DATE is NULL)) ORDER BY t0.CREATED_DATE ASC, t0.QUEUE_ITEM_PK ASC LIMIT 50
>> 
>> (2) Remove the slow sort field - Takes about 72ms for MySQL to return some values.
>> SELECT RTRIM(t0.CONFIG), t0.CREATED_DATE, t0.IDENTIFIER_1, t0.IDENTIFIER_2, t0.IDENTIFIER_3, t0.IDENTIFIER_4, t0.ITEM_DATE, t0.MODIFIED_DATE, t0.QUEUE_DETAILS_FK, t0.QUEUE_ITEM_PK, t0.QUEUE_TAG, t0.STATUS FROM queue_item t0 WHERE (t0.QUEUE_TAG = 'mb:nui:RENDER_MEDIA' AND (t0.ITEM_DATE < '2013-08-08 16:46:17 Etc/GMT' OR t0.ITEM_DATE is NULL)) ORDER BY t0.QUEUE_ITEM_PK ASC LIMIT 50
>> 
>> Now, in our app, during the objectsWithFetchSpecification(..)
>> (1) freezes the app totally.. no error messages, just frozen.
>> (2) works fine.
>> 
>> Any thoughts?
>> 
>> Thanks, 
>> 
>> Mark
>> 
>> 
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> -- 
> Chuck Hill             
> Executive Managing Partner, VP Development and Technical Services
> 
> Practical WebObjects - for developers who want to increase their overall knowledge of WebObjects or who are trying to solve specific problems.    
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