I would like haproxy to use its own 503 document page when back server (backend) sends HTTP 503 code. Is it possible?
Have seen something like "monitor fail" conditions but don't know how to add it to the frontend.
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You can use the
errorfile directive and then a custom
.http text file. So for example:
errorfile 503 /etc/haproxy/errors/503-mycustom.http
Content of the file would then be something like:
HTTP/1.0 503 Service Unavailable Cache-Control: no-cache Connection: close Content-Type: text/html <html> <head> <title>RARRR!!!!!</title> </head> <body style="font-family:Arial,Helvetica,sans-serif;"> <div style="margin: 0 auto; width: 960px;"> <h2 >RAWR RAWR RAWR</h2> </div> </body> </html>
errorfile directive can be specific to a backend as well.
The "errorfile" setting cannot be used to change a response sent by HAProxy if nodes are online. This setting only affects HAProxy when all nodes are offline.
It is important to understand that this keyword is not meant to rewrite errors returned by the server, but errors detected and returned by HAProxy. This is why the list of supported errors is limited to a small set.
There is something dirty you can do. You can block responses 503, which will result in returning the custom 502 error for which you can build an error page. However, keep in mind that any reason haproxy would have to return a 502 (invalid response) will return the same thing.
Basically it's as simple as "rspdeny ^HTTP/1.1 503" combined with "errorfile 502".