How to show an empty error page on HAProxy for a single URL

503-errorhaproxy

Question

I have a single URL say:

http://foo-backend.com/display_blank_when_errored

On a site behind an HAProxy load balancer let's say the front-end site is:

When an error happens 99% of the time I want to show the error pages configured with errorfile but only on this single page I want it to return a blank response. How would I go about doing this?

Background

This is using HAProxy 1.5.

I have a page that is being used around the internet in an IFrame and in the rare case that the server is down, rather than displaying an error page, I want it to display nothing so that the user experience is not affected.

Best Answer

You may use different backend section for specified URL. For example:

frontend webserver
   use_backend srv_noerrors if { url_beg /display_blank_when_errored }
   default_backend srv_werrors

backend srv_noerrors
   errorfile 503 /etc/haproxy/errors/503err_blank.http

backend srv_werrors
   errorfile 503 /etc/haproxy/errors/503err_info.http

Related Solutions

Iis – Measuring page response time for different servers in web farm (HAProxy?)

HAProxy provides very detailed statistics about all HTTP requests. Way more than you see on the stats page.

You need to setup a syslog server listening to UDP syslog messages (e.g. on localhost). That syslog server needs to be configured to write the log messages received by HAProxy to a file (or wherever you like it). An example HAproxy configuration could look like this:

defaults
  # send the logs to localhost:514 via UDP, using the local0 facility
  log 127.0.0.1 local0 debug
  option httplog

  mode http
  balance roundrobin

listen farm
  bind 10.0.0.1:80

  server iis1 10.0.1.1:80
  server iis2 10.0.1.2:80

See section 8 of the configuration manual for detailed information about the log format and how to set it up.

Nginx – Should Nginx be at the front of HAProxy or opposite

If you plan to have every web server available over HTTPS, then you'll need to install Nginx in front of HAProxy. With that configuration, your Nginx will handle all the SSL work and send the decrypted HTTP traffic directly to the HAProxy frontend, which will then load-balance requests to your web servers based on the rules you specify.

The idea of using LVS, as mentioned by womble is that it's somewhat less intrusive since it doesn't hold a connection between your web server and the client accessing the site. On the other hand, LVS will only provide you with simple load-balancing and won't allow you to forward requests based on file extension, requested URL, headers, etc. That's why HAProxy is used in many situations.

If you only need SSL on one server (non load-balanced) then you're safe to use HAProxy for everything without using Nginx. On the other hand you'll have one issue with being unable to see the client's source IP address in the web server's HTTPS logs (because HAProxy rewrites that address). The IP will be in HAProxy logs if you enable it though ;)

Best Answer

Related Solutions

Iis – Measuring page response time for different servers in web farm (HAProxy?)

Nginx – Should Nginx be at the front of HAProxy or opposite

Related Topic