Long delay in processing .pagespeed resources

[Glenn Slaven]

We're seeing intermittent very slow responses for .pagespeed resources, I've attached a debug log (running with a debug build of nginx).

There's around 8 seconds between

2018/02/12 06:58:32 [debug] 187717#0: *13682 http request count:2 blk:0

and 

2018/02/12 06:58:40 [debug] 187717#0: *13682 ps fetch handler: /template-resources/stylesheet/A.shopping-cart.css,qv=2017-01-18.pagespeed.cf.SBneiq5NEO.css

I've been looking through the source code for both pagespeed and nginx, I can see where these two log messages are writtem 

http request count: https://github.com/nginx/nginx/blob/release-1.11.10/src/http/ngx_http_request.c#L3395

ps fetch handler: https://github.com/apache/incubator-pagespeed-ngx/blob/v1.12.34.2-beta/src/ngx_pagespeed.cc#L270

but I'm not sure where the delay is coming from. 

Any help on where to look or how to get more debug information out would be appreciated.

Also, immediately following the ps fetch handler log message it logs HTTP/1.1 200 OK, is that the response from the background fetch to get the resource?  

We are running pagespeed 1.12.34.2 with nginx 1.11.10 on a site with varnish in front and using a shared memcache with the pagespeed MemcachedServers directive.  Pagespeed RewriteLevel is set to PassThrough with the following filters enabled

add_head,convert_meta_tags,extend_cache,inline_import_to_link,inline_javascript,lazyload_images,rewrite_images,rewrite_javascript,rewrite_style_attributes_with_url,fallback_rewrite_css_urls,flatten_css_imports,inline_css,rewrite_css

Thanks

Glenn

[Otto van der Schaaf]

Maybe the histograms on the admin pages [1] can show where time is spent.

https://www.modpagespeed.com/doc/admin

Otto

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