My customer's web application sometimes drops AJAX requests.
It's a LAMP site. Regular browser requests are uninhibited. The web app includes a slide show and that goes right on working.
However, logins involve an AJAX request (jQuery) and a couple times a day, the login requests will not work. The problem clears up in about 5 minutes.
When logins are failing, users logged in can do most operations but if they're doing other operations involving AJAX requests (certain add/edit operations), those also do not respond.
The Apache logs do not record the requests.
The problem is reported to always occur at the same time in the hour 40-45 minutes past the hour. I haven't proven this, but the customer is fairly sure.
Figuring out what happens at that time of the hour is one approach I'm working on. The obvious cron job fires every 15 minutes, not just as the 40-45 mark.
But WHAT kind of thing am I looking for? Both TOP and my VM stats indicate normal usage of CPU & RAM. The VM stats indicate normal network & disk usage.
I've upgraded to the latest jQuery and I've moved my static files off to a separate server running Lighttpd. The DB is on another VM on the same host. Its usage stats fail to show anything unusual at the problem times as well.
What else should I be looking at?
Thanks!
Copyright Notice：Content Author:「Daniel Wilson」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/35947837/server-sometimes-drops-ajax-requests