haproxy.conf

#
# This config file is a combination of ideas from:
#   http://www.37signals.com/svn/posts/1073-nuts-bolts-haproxy
#   http://www.igvita.com/2008/05/13/load-balancing-qos-with-haproxy/
#   http://wiki.railsmachine.com/HAProxy
#   http://elwoodicious.com/2008/07/15/nginx-haproxy-thin-fastcgi-php5-load-balanced-rails-with-php-support/
#   http://upstream-berlin.com/2008/01/09/using-haproxy-with-multiple-backends-aka-content-switching/
#   http://wiki.railsmachine.com/HAProxy
#   http://gist.github.com/raw/25482/d39fb332edf977602c183194a1cf5e9a0b5264f9
#

global
  # maximum number of simultaneous active connections
  maxconn 50000

  # run in the background (duh)
  daemon
  user  haproxy
  group haproxy

  # for restarts
  pidfile /var/run/haproxy.pid

  # Logging to syslog facility local0
  log   127.0.0.1       local0
  stats socket /var/run/haproxy.stat mode 777

  # Distribute the health checks with a bit of randomness
  spread-checks 5

  # Uncomment the statement below to turn on verbose logging
  #debug

# Settings in the defaults section apply to all services (unless you change it,
# this configuration defines one service, called rails).
defaults

  # apply log settings from the global section above to services
  log global

  # Proxy incoming traffic as HTTP requests
  mode http

  # Unfortunately, per the haproxy docs, connection-based load balancing is
  # not a good strategy for HTTP
  balance roundrobin

  # Maximum number of simultaneous active connections from an upstream web server
  # per service
  maxconn 25000

  # Log details about HTTP requests
  option httplog

  # Abort request if client closes its output channel while waiting for the 
  # request. HAProxy documentation has a long explanation for this option.
  option abortonclose

  # Check if a "Connection: close" header is already set in each direction,
  # and will add one if missing. Also add X-Forwarded-For header
  option httpclose
  option forwardfor 

  # If sending a request to one server fails, try to send it to another, 3 times
  # before aborting the request
  retries 3

  # Do not enforce session affinity (i.e., an HTTP session can be served by 
  # any Mongrel, not just the one that started the session
  option redispatch

  # Keep timeouts at web speed, since this balancer sits in front of everything
  # Backends will force timeout faster if needed.
  timeout client  30s
  timeout connect 30s
  timeout server  30s

  # For the frontend balancer, check the health of haproxy monitor URL.
  # This avoids a double-check; haproxy will say 503 if backends are 503
  option httpchk HEAD /haproxy?monitor HTTP/1.0

  # Amount of time after which a health check is considered to have timed out
  timeout check 5s

  # Enable the statistics page
  stats enable
  stats uri     /haproxy?stats
  stats realm   Haproxy\ Statistics
  stats auth    admin:yourpasswordhere
  stats refresh 5s

# this is where you define your backend web clusters. 
# you need one of these blocks for each cluster
# and each one needs its own name to refer to it later.
# Note: The "cluster:serviceport" is just a *name*, the port is not used
listen http-webservices 0.0.0.0:80

  # Create a monitorable URI which returns a 200 if at least 1 server is up.
  # This could be used by Traverse/Nagios to detect if a whole server set is down.
  acl servers_down nbsrv(servers) lt 1
  monitor-uri /haproxy?monitor
  monitor fail if

  # add a line for each EC2 web server
  # this is typically generated via script 
  server 10.0.0.x:80 10.0.0.x:80 maxconn 25 check inter 5s rise 3 fall 2


listen https-webservices 0.0.0.0:443
  # set mode from http to tcp because haproxy can't use SSL on it's own
  mode tcp
  # use haproxy's built in ssl check
  option ssl-hello-chk

  # again, one line per server
  server 10.0.0.x:443 10.0.0.x:443 maxconn 25 check inter 5s rise 18 fall 2