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isNaN1247
Asked: 2011-03-20 07:44:44 +0800 CST

How can I remove balanced node from haproxy via command line?

  • 772

I have haproxy running as my load-balancer and from the stats web interface that comes with haproxy, I can put a web server into maintenance mode (and bring it back out again) - which is great!

However, I also want to be able to perform that same action from the command line (for use in some automated deployment workflows). Is this possible, and if so how?

Many thanks

load-balancing haproxy

7 Answers

  1. Best Answer

    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.

    • 64

  2. In addition to beardwizzle's echo method, you can also do this interactively:

    root@ny-lb01:/etc/haproxy# sudo socat readline /var/run/haproxy.stat 

prompt
> set timeout cli 1d
> disable server foo/web01
> help
Unknown command. Please enter one of the following commands only :
  clear counters : clear max statistics counters (add 'all' for all counters)
  clear table    : remove an entry from a table
  help           : this message
  prompt         : toggle interactive mode with prompt
  quit           : disconnect
  show info      : report information about the running process
  show stat      : report counters for each proxy and server
  show errors    : report last request and response errors for each proxy
  show sess [id] : report the list of current sessions or dump this session
  show table [id]: report table usage stats or dump this table's contents
  get weight     : report a server's current weight
  set weight     : change a server's weight
  set timeout    : change a timeout setting
  disable server : set a server in maintenance mode
  enable server  : re-enable a server that was previously in maintenance mode
    • 21

  3. On the off chance that you only have access to netcat (nc) you can use it to interact with HAProxy's socket file in a similar fashion to socat.

    $ echo "show info" | nc -U /var/lib/haproxy/stats | head -10
Name: HAProxy
Version: 1.5.2
Release_date: 2014/07/12
Nbproc: 1
Process_num: 1
Pid: 29745
Uptime: 0d 0h14m35s
Uptime_sec: 875
Memmax_MB: 0
Ulimit-n: 8034

    To disable a server:

    $ echo "enable server bk_dservers/ds02" | nc -U /var/lib/haproxy/stats

    Take care to make sure that the socket file has the appropriate level of access to perform the above. Mainly something like this:

    stats       socket /var/lib/haproxy/stats level admin

    Otherwise you'll get permission denied errors:

    $ echo "disable server bk_dservers/ds02" | nc -U /var/lib/haproxy/stats
Permission denied

$

    References

    • 9

  4. The easy way is:

    1 - Configure your web server to return 503 code if a file named maintenance.html (for example) exists. With apache you can do it as follows:

    <IfModule mod_rewrite.c>
  RewriteEngine On
  RewriteCond %{ENV:REDIRECT_STATUS} !=503
  RewriteCond "/var/www/maintenance.html" -f
  RewriteRule ^(.*)$ /$1 [R=503,L]
</IfModule>

    2 - Configure your haproxy backend to check an URL instead of only checking a port as follows:

    backend site
    balance roundrobin
    option httpchk GET /index.html
    server myserver1.example.com 192.0.2.1:80 cookie S1 check inter 2000 fall 3
    server myserver2.example.com 192.0.2.2:80 cookie S2 check inter 2000 fall 3

    3 - Restart your webserver and load balancer.

    4 - Put your web server in maintenance mode.

    touch /var/www/maintenance.html

    5 - Remove your web server from maintenance mode.

    rm -f /var/www/maintenance.html
    • 7

  5. You can also temporarily "remove" the health check page from one server, to get the endpoint down and then publish your application.

    • 2

  6. In HAProxy 1.8 you can also use set server state:


    put the server in maintenance (or drain) mode:

    echo "set server backend_name/sever_name state maint" | socat stdio /path_to_admin_socket_file
echo "set server backend_name/sever_name state drain" | socat stdio /path_to_admin_socket_file

    put the server back to ready mode:

    echo "set server backend_name/sever_name state ready" | socat stdio /path_to_admin_socket_file
    • 1

  7. If you have debian, readline does not work, netcat is a better option for interactive:

    user@server:/etc/haproxy$ sudo nc -U /etc/haproxy/haproxysock
prompt
> show info
Name: HAProxy
Version: 1.7.11-1ppa1~xenial
Release_date: 2018/04/30
Nbproc: 1
Process_num: 1
Pid: 12307
Uptime: 0d 10h33m22s
...

    Non Interactive:

    echo "show info;show stat" | sudo nc -U /etc/haproxy/haproxysock
    • 0