Occasional asset 404's - how to debug?

[Chris W]

Hi there,

We're a regular user of mod_pagespeed; 7 servers, 500+ sites for 5 years or more. By and large, it's just worked. It's been great.

At the moment we have a new site & server with issues, but I'm unsure how to debug it. Can anyone point me to a good resource? Or how to collect info that would help those who are kind enough with their time here?

In summary:

• We have 10 sites on a new server; Centos 7, PHP7, WordPress
• WP is fairly normal, no supercache, totalcache or anything
  
• 2 of the sites use SSL on all requests - these sites have an issue only - not the non-secure ones
  
• The issue is that, maybe once or twice a week, we spot a page where requests to some of the the optimised assets throw a 404

Here are some of the request paths:

1. https://www.some-site.co.uk/wp-content,_plugins,_contact-form-7,_includes,_js,_scripts.js,qver==4.5+js,_jquery.matchHeight.js,qver==4.6+js,_back-to-top.js,qver==4.6.pagespeed.jc.xi4xrUjGEx.js
2. https://www.some-site.co.uk/js,_phone-menu.js,qver==1+wp-includes,_js,_jquery,_ui,_core.min.js,qver==1.11.4+wp-includes,_js,_jquery,_ui,_datepicker.min.js,qver==1.11.4.pagespeed.jc.zYbEK42-oi.js
3. https://www.some-site.co.uk/wp-content/plugins/duracelltomi-google-tag-manager/js/gtm4wp-contact-form-7-tracker.js,qver==1.3.2+gtm4wp-form-move-tracker.js,qver==1.3.2.pagespeed.jc.2QN08ptA7t.js
4. https://www.some-site.co.uk/wp-content/uploads/2016/07/x197-my-image-1411x350.jpg.pagespeed.ic.rjXpem5Lav.webp
   

It might be a red herring, but paths 1 & 2 seem to be missing slashes?

Clearing the mod_pagespeed cache fixes the page. Browsing on a different user agent or switching to a logged in/out session seems to find a copy in the mod_pagespeed cache that works fine.

How would I begin to debug this?

Being a live site, I've had to turn mod_pagespeed off. Happening so infrequently means it's hard to find examples!

Many thanks,
Chris

[Chris W]

Hi,

I just wanted to bump this one up to see if anyone can point me in the right direction.

Are there any how-to's on ways to debug mod_pagespeed issues?

As this only affects sites on HTTPS, are there any pitfalls I should be aware of compared to configuring non-SSL sites?

Many thanks,
Chris

[Otto van der Schaaf]

Do you see lines mentioning "Serf status 113" in the logs around the time the problem shows up?

There have been other similar reports, see https://github.com/pagespeed/ngx_pagespeed/issues/1267

and https://groups.google.com/forum/#!topic/ngx-pagespeed-discuss/lNtYJyPL9mI

It would be helpful to check the error and access logs for messages that could be related.

Otto