Dynamic HAProxy configuration

haproxyload balancing

I try to figure out a way to dynamically manage the loadbalancer configuration.

I want to add and remove "service nodes" depending on the overall system load.

My research so far revealed "Thalassa" https://github.com/PearsonEducation/thalassa/blob/master/README.md which uses Node.JS + Seaport to manage clients and then updates the HA-Proxy configuration

Still I am not convinced if Thalassa is stable enough to be used in productive systems. Are there usable alternatives out there which offer the same features ?

Best Answer

If you authorize your stats socket, you can send commands to it.

From the 1.4 documentation

disable server <backend>/<server>

Mark the server DOWN for maintenance. In this mode, no more checks will be performed on the server until it leaves maintenance. If the server is tracked by other servers, those servers will be set to DOWN during the maintenance.

In the statistics page, a server DOWN for maintenance will appear with a "MAINT" status, its tracking servers with the "MAINT(via)" one.

Both the backend and the server may be specified either by their name or by their numeric ID, prefixed with a sharp ('#').

This command is restricted and can only be issued on sockets configured for level "admin".

You can use this to effectively add and remove servers from active service.

Barring that, you can use option httpchk and block the check requests on the appserver side when a server should leave or join the balancing group. This requires some means to centrally manage that, of course.

Related Solutions

How to set up stats for HAProxy

That is not correct. There would be a stats page on http://yoursite.com:1935/haproxy?stats

To overcome this add another listener-

listen stats :1936
    mode http
    stats enable
    stats hide-version
    stats realm Haproxy\ Statistics
    stats uri /
    stats auth Username:Password

Then go to http://yoursite.com:1936/ and login.

Make sure your firewall isn't blocking this request.

HAProxy – How to Remove a Balanced Node via Command Line

Update (28 Aug 2012): I now tend to use haproxyctl nowadays, which utilizes the methods described below.

I've fixed it after a little more research, for anyone else with the same issue:-

You can add a unix socket in your config, then interact with that (here are the possible commands).

To set up:

sudo nano /etc/haproxy/haproxy.cfg

In your 'global' section add in:

stats socket /etc/haproxy/haproxysock level admin

Restart your haproxy daemon (e.g. sudo service haproxy restart)

Now you need socat (if you don't have it, just apt-get install socat on Ubuntu).

Now all you need to do is fire off this command to take down a node:

echo "disable server yourbackendname/yourservername" | socat stdio /etc/haproxy/haproxysock

To bring it back up replace disable with enable in the command above.

Best Answer

Related Solutions

How to set up stats for HAProxy

HAProxy – How to Remove a Balanced Node via Command Line

Related Topic