Re: objectsWithFetchSpecification freezes during a slow call

On 2013-08-08, at 12:21 PM, Mark Gowdy wrote:

> 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. 

The jstack may suggest where it is happening.

> 
>> 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. 

No, it should not.  I have several apps that have much longer running queries and it is not a problem for EOF.  I am pretty sure you will find the problem lies in MySQL.


Chuck


> 
>> 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.    
>> http://www.global-village.net/gvc/practical_webobjects
>> 
>> Global Village Consulting ranks 13th in 2012 in BIV's Top 100 Fastest Growing Companies in B.C! 
>> 
>> Global Village Consulting ranks 44th in 25th annual PROFIT 500 ranking of Canada’s Fastest-Growing Companies by PROFIT Magazine!
>> 
>> 
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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.    
http://www.global-village.net/gvc/practical_webobjects

Global Village Consulting ranks 13th in 2012 in BIV's Top 100 Fastest Growing Companies in B.C! 

Global Village Consulting ranks 44th in 25th annual PROFIT 500 ranking of Canada’s Fastest-Growing Companies by PROFIT Magazine!













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