Openshift + HAproxy 503 custom page

Question

I'm using 503 HTTP Status and a coming soon page for maintenance mode.

Is there any way to get HAproxy serving server-side generated 503 page instead of the default blank/unavailable page?

I'm using Openshift + HAproxy + Cloudflare + PHP.

Thanks in advance.

Haproxy config (some comments removed):

#--------------------------------------------------------------------- # Global settings #--------------------------------------------------------------------- global log 127.0.0.1 local2 chroot /var/lib/haproxy pidfile /var/run/haproxy.pid maxconn 4000 user haproxy group haproxy daemon # turn on stats unix socket stats socket /var/lib/haproxy/stats #--------------------------------------------------------------------- # common defaults that all the 'listen' and 'backend' sections will # use if not designated in their block #--------------------------------------------------------------------- defaults mode http log global option httplog option dontlognull option http-server-close option forwardfor except 127.0.0.0/8 option redispatch retries 3 timeout http-request 10s timeout queue 1m timeout connect 10s timeout client 1m timeout server 1m timeout http-keep-alive 10s timeout check 10s maxconn 3000 #--------------------------------------------------------------------- # main frontend which proxys to the backends #--------------------------------------------------------------------- frontend main *:5000 acl url_static path_beg -i /static /images /javascript /stylesheets acl url_static path_end -i .jpg .gif .png .css .js use_backend static if url_static default_backend app #--------------------------------------------------------------------- # static backend for serving up images, stylesheets and such #--------------------------------------------------------------------- backend static balance roundrobin server static 127.0.0.1:4331 check #--------------------------------------------------------------------- # round robin balancing between the various backends #--------------------------------------------------------------------- backend app balance roundrobin server app1 127.0.0.1:5001 check server app2 127.0.0.1:5002 check server app3 127.0.0.1:5003 check server app4 127.0.0.1:5004 check 

Answer 1

Is there any way to get HAproxy serving server-side generated 503 page instead of the default blank/unavailable page?

This isn't the actual question you should be asking. HAProxy always uses the server's response. The error file is only used for errors generated internally by HAProxy.

If you check your web server logs, you'll find that these specific requests are not actually being sent to the web server.

This is happening because HAProxy thinks your server is down... because it's getting 503 from the server in response to the health check.

If the server were returning 502 or 400 or any error code on the health checks, you'd still receive the 503 from HAProxg because the server is, officially, down.

WARNING] 201/142518 (192371) : Server express/local-gear is DOWN, reason: Layer7 wrong status, code: 503, info: "HTTP status check returned code <3C>503<3E>", check duration: 87ms. 0 active and 0 backup servers left. 0 sessions active, 0 requeued, 0 remaining in queue 

You have apparently redacted the line option httpchk from the configuration you posted, but it has to be there, or HAProxy would only do a layer 4 check, and this wouldn't be happening.

The simplest solution is to remove that line from the backend or default config.

Answer 2

Yes. Use the errorfile directive, for example via:

errorfile 503 /etc/haproxy/errors/503.http 

The syntax is as follows:

errorfile <code> <file> 

Quoting the docs:

<code> is the HTTP status code. Currently, HAProxy is capable of generating codes 200, 400, 403, 405, 408, 429, 500, 502, 503, and 504. <file> designates a file containing the full HTTP response. It is recommended to follow the common practice of appending ".http" to the filename so that people do not confuse the response with HTML error pages, and to use absolute paths, since files are read before any chroot is performed. 

For example, the content of the file could be:

HTTP/1.1 503 Service Unavailable\r\n Cache-Control: no-cache\r\n Connection: close\r\n Content-Type: text/html\r\n <html> <head> <title>Service unavailable</title> </head> <body> <h1>Service unavailable</h1> </body>