haproxy doesn't aggregate relation data from multiple units

[Andreas Hasenack]

Setting the services via relation data is broken when you have more than one unit.

For example, I created a simple fake webapp charm and related it to haproxy:
juju deploy haproxy
juju deploy andreas-webapp
juju add-relation haproxy:reverseproxy andreas-webapp:website

This is the website-relation-changed hook on andreas-webapp:
"""
#!/bin/sh
host=$(unit-get private-address)
port=80
relation-set "services=
- { service_name: message,
    service_options: [mode http, balance leastconn, option httpchk GET / HTTP/1.0],
    servers: [[message, $host, $port, check inter 5000 rise 2 fall 5 maxconn 4],
              [message, $host, $(($port+1)), check inter 5000 rise 2 fall 5 maxconn 4]]
  }
"
"""

After the first unit was related, this is the haproxy backend entry:
"""
backend message
    mode http
    balance leastconn
    option httpchk GET / HTTP/1.0
    server message 10.55.32.119:80 check inter 5000 rise 2 fall 5 maxconn 4
    server message 10.55.32.119:81 check inter 5000 rise 2 fall 5 maxconn 4
"""

Now I add another unit of my webapp:
juju add-unit andreas-webapp

Here is a diff of the haproxy.cfg file after the second unit established the relation:
--- /etc/haproxy/haproxy.cfg.before 2014-01-20 21:25:40.653634221 +0000
+++ /etc/haproxy/haproxy.cfg 2014-01-20 21:28:25.933632737 +0000
@@ -26,8 +26,8 @@
     mode http
     balance leastconn
     option httpchk GET / HTTP/1.0
- server message 10.55.32.119:80 check inter 5000 rise 2 fall 5 maxconn 4
- server message 10.55.32.119:81 check inter 5000 rise 2 fall 5 maxconn 4
+ server message 10.55.32.174:80 check inter 5000 rise 2 fall 5 maxconn 4
+ server message 10.55.32.174:81 check inter 5000 rise 2 fall 5 maxconn 4

 frontend haproxy-0-80
     bind 0.0.0.0:80

The haproxy charm just replaced the data, instead of adding/aggregating it.

[Andreas Hasenack (ahasenack)]

Sample webapp charm descibed in the ticket that can be used to reproduce the problem.