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enter image description hereI'm having problem in our extjs php application. We have two server and there is a load balancing (NLB) in there working in a round robin way . While using the system the user is having some problems like data is not loading from the database and also the http requests are being aborted. I don't know actually from where we will start our troubleshooting.

On any particular page in the website, when you opened a page, a number of the assets (user info, dropdown, the whole page also etc) failed to load. If you refreshed, the page may work fine, the same set of assets may fail to load or different assets may fail to load.

There was nothing in any of the apache logs about the requests that failed, however since it seemed to point to an apache issue, we restarted apache. The first time we tried, it made no difference but about 10 minutes later, in the absence of a better solution we tried again. Bizarrely, the problem disappeared immediately. And again come after 1-2 days.

I have also made the process php to multiple, so that different request get different php file but looks like the issue is not there.

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1 Answer 1

The problem description was very general but there are a few things you can try to zero in on the cause of the issue:

  • Check the HTTP return codes for all apps using Chrome (F12), FireBug in FireFox or something similar. This type of error you are getting and on which resources should point you in the right direction.
  • Set the error reporting in PHP to E_ALL while testing and recheck the Apache logs.
  • Check all logs for relevant errors and warning (system, database, security, etc...).
  • Bypass the load balancer and access the servers directly.
  • Add manual logging output in your application to narrow down where things work and don't work.

If the issue is intermittent you'll need to find a way to duplicate the issue. Try load testing with ApacheBench or a similar program. Once you can regularly duplicate it then it is just a matter of zeroing in on where it is occurring and why.

EDIT:

My guess from your pictures is that app crashed, likely in a manner that prevented an error message from being output (assuming there still isn't one). If it is always that one application that is crashing you can limit your investigation to that one app. Is it specific input that causes it to crash, is it load based, is it seemingly random, etc...? You can also temporarily add manual error_log() messages to the app to narrow down where it is crashing.

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I have also updated the post with picture. The network part is not in my hand and I have less knowledge in NLB. –  Farhan Dec 21 '12 at 6:14
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