Google page speed service is the most effective method to improve page loading time. Google Page speed servers will request data from real(origin) servers and optimize it to improve client side performance. Google is added new non-stranded error codes Like HTTP 520 to represent when it have problems to receive data from origin servers. The HTTP 520 Error indicate possible Request timeout error. The HTTP 52X error indicate problems with origin server and do not indicate any internal problems with PSS service itself.
Following are the some possible causes of the problem.
TIMEOUT – Origin servers accepted the connection but fails complete the request.Please check you have any server side problems to load the page.
CLOSED – Origin server closed the connection to PSS servers
DISCONNECTED – Please make sure that you are using X-Forwarded-For header to identify user IP. The web servers may treat many requests coming from same IP and may block the IP address
CONNECTION_ERROR: Google Page Speed servers have some connection problem to connect to origin server.
TROUBLESHOOTING HTTP 520 ERROR
To troubleshot HTTP 520 Error you first need to disable PSS rewrites in control panel. If HTTP 520 Error reappear you need to check whether the same page is loaded using origin server URL. The Web server will that it is receiving requests from same IP address(Address of PSS service) and bleck the IP address number of request per second reached it throttle value. The servers must use X-Forwarded-For header other than requested IP address to identify the user.