Hello all,
Long time moodle user, but first time poster here.
Just wondering if I might be able to get people's thoughts on this issue we are experiencing here and hopefully how to resolve it. First, the information about our config:
Moodle info:
Using php accelerator APC.
Moodle usage stats: around 500 registered users, maximum around 30 concurrent users
Server info:
Dual Quad core Xeon, 12GB ram, 7200rpm enterprise sata disks, gigabit ethernet. Running Opensuse 12.1 x64. Server is located on site, but is accessed across the internet via our 20Mbit link.
- Everything runs great both locally and externally. With debugging on in moodle, I can see that page load times are typically around 0.5 seconds, even for courses with lots of content.
- As a non-editing user (such as a student) everything works fine in whatever browser is used (Internet Explorer, Firefox, Chrome).
- I've used tools such as the mysqltuner perl script to ensure the database is properly configured
- Have checked for missing database indexes (there are none).
- Summary- this is a brand new server especially purchased for our moodle instance, and everything runs great other than the issue I describe below.
The Problem:
- As an editing user (such as a teacher), if you enter a course where you have editing rights and click 'turn editing on' the problem starts:
- In Chrome or Firefox, there is a noticeable delay while the course reloads with editing on. During this time the browser appears unresponsive (and in some cases the computer will actually report the browser program as being 'non-responsive' Typically this situation lasts around 15 seconds, and then the course finishes loading successfully
- In Internet Explorer (8 or 9) the problem is much worse. In around 90% of my testing, when I try to edit a course in Internet Explorer the browser becomes unresponsive and never recovers. Once or twice the browser reports that a 'script is taking to long to load' and gives me the option to stop the script, but this doesn't appear to do anything.
- In summary- turning editing on inside a course causes (at best) a 15 second page load time or (at worst) a non-responsive/crashed browser, depending on what browser is being used.
What I've tried so far / observations:
- I have the performance/debugging information being printed on the footer of each moodle page, however it doesn't seem to reflect the 'real world' page load time. For example, for a course in editing mode in will typically list a load time of around 2 seconds, when in actual fact it took around 15 seconds for the page to become responsive after turning on editing.
- I've noticed that when editing a course it does appear to be causing higher than expected CPU usage on the client. For example, on a test machine (Pentium D 3ghz, 1gb ram, Win7, FIrefox 13) the Firefox process uses about 50% CPU during the period when the browser appears 'frozen'. Even after the browser has become responsive again, CPU usage remains at around 30-40% for the Firefox process even when I'm just sitting on the page doing nothing.
- I've tried to use the Firebug addon for Firefox and the internal element inspecting tools of Chrome to narrow down what is causing the freezing/slowness, but I don't have much experience with this. If anyone can suggest what I should be looking for I'd greatly appreciate it.
For the moment, I'm just asking teaching staff to use Firefox if they are editing courses. The problem doesn't impact our students since they aren't editing anything.
Apologies for the long post. Just wanted to make sure I included as much information as possible. If there is additional information I can provide that would be helpful please let me know.
So, if anyone has tips or suggestions about how I can resolve this issue I would really appreciate your input. As mentioned using a browser other that IE is a workaround that will suffice for the short term, but I'd like to get to the bottom of it.
Thanks in advance for your replies.
