Error 503 Backend fetch failed

Question

Sometimes I get this error when I am developing some application in wordpress, someone knows tell me the reason???

Answer 1

Let’s get started, the Varnish is a "accelerator", it’s a page caching system, it’s a reverse proxy, that is the requests go through it and the copies are stored in memory.

Generally this error occurs when it exceeds the storage limit in memory, you can edit the file the file varnish (or varnish.params) and adjust parameter http_resp_hdr_len so that the server can support higher consumption (it also depends on how much memory your server has available for the service, if it is Shared is likely to be very limited).

Configuration files in different distros:

• Centos 6: /etc/sysconfig/varnish
• Centos 7: /etc/varnish/varnish.params
• Ubuntu: /etc/default/varnish

However if you don’t have access to the settings just by contacting the hosting.

Let me make one thing clear, I am not advocating the lodgings most have small problems even that often cause inconvenience, but this problem most of the time it is the fault of web-developers and site administrators (in case you probably), who inject numerous javascript, css, plugins and add-ons needlessly and with this they are making the site increasingly heavy and slow, even with incredible caching systems and etc the server has no way of coping.

In other words, it’s not really a configuration problem, but rather a problem of misuse of resources, so you can try to have a general review, analyze if everything is necessary or even think about changing Wordpress for a more efficient platform, apart from this there is not much to do.