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I'm receiving some sporadic high server load on a Drupal application (really high. 8 cores, load average of 50). The load is normally sitting between 5-10.

The Drupal application sits behind a separate Varnish server, which keeps things looking peachy for most anonymous users.

The Drupal application itself is quite heavy (working on this, but we have more immediate requirements). When we've had big issues with this in the past, it's when anonymous users have been bypassing Varnih.

I can see that the number of requests to Nginx (bypassing Varnish) is increasing during these times, but I'm not sure what to do about it. I'm also sure that the number of authenticated users isn't significantly increasing in these periods.

How do I approach troubleshooting this problem?

HopelessN00b
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rca86
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  • Pretty much any web log analysis program will do this. So will Google Analytics or Piwik. – EEAA Jan 27 '15 at 13:23

1 Answers1

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The command varnishtop -b will allow you to see what's bypassing Varnish and hitting the backend. Looking at those requests, if any of them should not be, you have a good starting point for modifying your VCL to fix it. Otherwise, it'll at least tell you the most common hits that are reaching your backend. Based on that, you can then start to make smart choices on which page(s) to profile further (e.g. with XHProf or a tool like NewRelic or AppNeta).

BMDan
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