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502 Bad Gateway

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Could somebody please explain why I get this

 

post-10632-1159605985.png

 

error with some theads? TIA!

 

/al

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Could somebody please explain why I get this

 

post-10632-1159605985.png

 

error with some theads? TIA!

 

/al

Hi, al.

 

A server (not necessarily a Web server) is acting as a gateway or proxy to fulfil the request by the client (e.g. a Web browser or a CheckUpDown robot) to access the requested URL. This server received an invalid response from an upstream server it accessed to fulfil the request.

 

This usually does not mean that the upstream server is down (no response to the gateway/proxy), but rather that the upstream server and the gateway/proxy do not agree on the protocol for exchanging data. Given that Internet protocols are quite clear, it often means that one or both machines have been incorrectly or incompletely programmed.

 

502 errors in the HTTP cycle

 

Any client (e.g. your Web browser or our CheckUpDown robot) goes through the following cycle when it communicates with a Web server:

 

* Obtain an IP address from the IP name of a certain site (the site's URL without the leading 'http://'). This lookup (conversion of IP name to IP address) is provided by domain name servers (DNSs).

* Open an IP socket connection to that IP address.

* Write an HTTP data stream through that socket.

* Receive an HTTP data stream back from the Web server in response. This data stream contains status codes whose values are determined by the HTTP protocol.

 

This error occurs in the final step above when the client receives an HTTP status code that it recognises as '502'.

 

This problem is entirely due to poor IP communication between back-end computers, possibly including the Web server. Only the people who set up the network at the site which hosts the Web server can fix this problem.

 

Use of proxies and caching is increasing on the Web. A CheckUpDown robot will always try to 'drill through' to the real computer that actually hosts the Web site, but the provider does not have complete control over where our HTTP request actually ends up. If only one link in the chain of computers dealing with our HTTP request is broken, then an error such as 502 can easily occur.

 

Whenever you encounter 502 errors - there is nothing YOU can do to sort them out...

 

Hope this helps a bit...

 

Paul Wynant

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Paul, thank you very much for pointing things out. ;)

 

The question was meant a little different: these errors don't occur purely random. They occur sometimes; only on showtopic URLs; and topics that are broken stay broken on reload; and if I use the same URL with a different browser (a different session), it works.

 

So this is something the one that provides this service for KL has to fix... and should know of... ;)

 

/al

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