Wordpress on nginx + php-fpm partially slow

Question

I'm hosting wordpress on a debian machine with nginx and php-fpm. Sometimes, especially on the first request, the performance is not amazing: It tooks up to 2,7 seconds only for generating the html source! But when I refresh the page it will go down to about 700ms sometimes. For me it seems an issue with the theme or a plugin, because on the same server I have a second wordpress installation which is using the same server-side configuration, but load always quite fast (~400s for html generation!).

My suspicion is that the theme or a plugin is doing some slow remote requests, because there are also widgets included who are eg loading the amout of likes from a facebook-page, which will even slow down more the generation time. I would like to look for a way to debug the causes of this problem. I'm thinking of a possibility for example to catch all remote requests to functions like file_get_contents, curl and so on.

I sure can disable every single plugin and install another theme to isolate the problem. But as a single plugin can be build on thousands lines of code, it would be cost much time to find the issue. Is there any kind of debugging here which can help to find the problem more quickly? XDebug seems to offer something like this but I never worked with it and currently I don't have really time to get familar with it.

Answer 1

Any external api calls on initial page load will indeed slow rendering time. For social websites, you can use ajax after page load, or even better, query those social websites once a day then store the results in a simple db table, for example wp_social_data, and cache it or index it or store the results a Json file or any other solution that works for you, then render on page load the data you stored instead of making an external http/s call. This will solve the external api calls part.

For nginx and php-fpm, in general : compression should be enabled, caching for static assets or pages, and some realistic values for other settings should be in place, depending on the your application. You can find Wordpress recommendation for nginx server block on here