How to create multiple haproxy instance separate processes for different configuration listeners with systemd on single Linux server

Tuesday, 30th August 2022


In this aticle will be explained, howto configure multiple haproxy instances with separate haproxy binary wrappers and configs to run on the same Linux server host
by creating and using systemd additional .services.

Usually haproxy as installed and  ran standard on Linux swapns 2 listener processes which are configured to serve any proxy configuration setup inside /etc/haproxy/haproxy.cfg.

Here is example:

[root@haproxy2:~ ]# ps -ef|grep -i haproxy
root      128464       1  0 Aug11 ?        00:01:19 /usr/sbin/haproxy -Ws -f /etc/haproxy/haproxy.cfg -p /run/ -S /run/haproxy-master.sock
haproxy   128466  128464  0 Aug11 ?        00:49:24 /usr/sbin/haproxy -Ws -f /etc/haproxy/haproxy.cfg -p /run/ -S /run/haproxy-master.sock

However what if you need to have a multiple services to be proxied and you need to have multiple configuration files separated under various
/etc/haproxy/ stored files (.e.g /etc/haproxy/haproxy-customer1.cfg /etc/haproxy-customer2.cfg /etc/haproxy-custmXYZ.fg) etc. , what then how this can be done ?

Besides the many down sides of involving systemd into Linux, there is some good sides of it, as on any modern Linux there is a separate service to manage haproxy as of year 2022 on most modern Linuxes Debian / CentOS / Redhat the location where usually systemd service scripts are located is under directory /usr/lib/systemd/system/ the systemd managed service files are with extension .service

[root@haproxy2:/usr/lib/systemd/system ]# ls -al haproxy.service
-rw-r–r– 1 root root 1509 Sep  5  2021 haproxy.service

[root@haproxy2:/usr/lib/systemd/system ]# ls -al cron.service
-rw-r–r– 1 root root 316 Feb 23  2021 cron.service

[root@haproxy2:/usr/lib/systemd/system ]# ls -al networking.service
-rw-r–r– 1 root root 643 Sep 21  2020 networking.service

[root@haproxy2:/usr/lib/systemd/system ]# ls -al systemd-journald.service
-rw-r–r– 1 root root 1812 Jul 13  2021 systemd-journald.service

1. Create new haproxy-custom.service and /etc/haproxy.cfg file copies

Adding new services that will be managed by systemd is pretty simple hence, you just need to have the original service file in that case this is haproxy.service and modify it a bit, original haproxy.service file on Red Hat Enterprise Linux release 8.5 (Ootpa) would look like this

Make exact copy of haproxy.service to haproxy-your-custom.service

[root@haproxy2:/usr/lib/systemd/system ]#  cp -vprf haproxy.service haproxy-customname.service
'haproxy.service' -> 'haproxy-customname.service'

[root@haproxy2:/usr/lib/systemd/system]# cp -vrpf /etc/haproxy/haproxy.cfg /etc/haproxy/haproxy_customname_prod.cfg
'/etc/haproxy/haproxy.cfg' -> '/etc/haproxy/haproxy_customname_prod.cfg'

2. Modify the new haproxy-customname.service and haproxy-custoname.cfg

a) Create hardlink copy of /usr/sbin/haproxy binary

It is a good idea to separte the haproxy executable binary for the additional systemd haproxy instance. This can be done either by copying /usr/sbin/haproxy to something like /usr/sbin/haproxy-customname-wrapper or by creating a hard link. As i'm cautious to keep the haproxy-customname-wrapper binary up2date and updated together once the haproxy rpm package / deb package is updated either with yum or apt depending on the Linux distro, hard link  use is always better.
Just for reference hardlink does keep an own copy of the binary data and occupies additional Filesystem inodes, but at the same time the first inode of the binary does point to the original binary, meaning that a package update will make the hardlink be updated up to the latest version of the file and no extra management of the hard linked haproxy-customname-wrapper is necessery.

[root@haproxy2:/usr/sbin ]# ln haproxy haproxy-custname-wrapper

[root@haproxy2:/usr/sbin ]#  ls -al haproxy-custname-wrapper
-rwxr-xr-x 2 root root 2541848 Sep  5  2021 haproxy-custname-wrapper*
root@haproxy2:/usr/sbin# ls -al haproxy
-rwxr-xr-x 2 root root 2541848 Sep  5  2021 haproxy*

b) Modify haproxy-custoname.service systemd instance

The original service file will have content like

Description=HAProxy Load Balancer

Environment="CONFIG=/etc/haproxy/haproxy.cfg" "PIDFILE=/run/"
ExecStartPre=/usr/sbin/haproxy -f $CONFIG -c -q $OPTIONS
ExecStart=/usr/sbin/haproxy -Ws -f $CONFIG -p $PIDFILE $OPTIONS
ExecReload=/usr/sbin/haproxy -f $CONFIG -c -q $OPTIONS

ExecReload=/bin/kill -USR2 $MAINPID



The modified one for the customname.service should have content similar to:

Description=HAProxy Load Balancer

Environment="CONFIG=/etc/haproxy/haproxy_customname_prod.cfg" "PIDFILE=/run/"
ExecStartPre=/usr/sbin/haproxy_customname -f $CONFIG -c -q $OPTIONS
ExecStart=/usr/sbin/haproxy_customname -Ws -f $CONFIG -p $PIDFILE $OPTIONS
ExecReload=/usr/sbin/haproxy_customname -f $CONFIG -c -q $OPTIONS

ExecReload=/bin/kill -USR2 $MAINPID


c) modify haproxy_customname_prod.cfg

Do the required config and save the file, below is minimal config sample:

[root@haproxy2:/etc/haproxy ]#  vim /etc/haproxy/haproxy_customname_prod.cfg

# Global settings
    log local6 debug
    chroot       /var/lib/haproxy
    pidfile      /run/
    stats socket /var/lib/haproxy/haproxy.sock mode 0600 level admin
    maxconn      4000
    user         haproxy
    group        haproxy

# common defaults that all the 'listen' and 'backend' sections will
# use if not designated in their block
    mode        tcp
    log         global
#    option      dontlognull
#    option      httpclose
#    option      httplog
#    option      forwardfor
    option      redispatch
    option      log-health-checks
    timeout connect 10000 # default 10 second time out if a backend is not found
    timeout client 300000
    timeout server 300000
    maxconn     60000
    retries     3


# round robin balancing between the various backends

frontend Frotnend_customname1
        mode tcp
        option tcplog
        #log global
        log-format [%t] %ci:%cp %bi:%bp %b/%s:%sp %Tw/%Tc/%Tt %B %ts %ac/%fc/%bc/%sc/%rc %sq/%bq

       default_backend Frontend_customname1

backend Frontend_customname1
        balance roundrobin
        timeout client 350000
        timeout server 350000
        timeout connect 35000
        server backend-server1 weight 1 check port 15000
        server backend-server2 weight 2  check port 15000


3. Reload systemd to make haproxy-customname.service known to systemctl, restart the freshly created service
and check its status


a) Execute daemon-reload to refresh known .service files in systemd

[root@haproxy2:/etc/haproxy ]# systemctl daemon-reload
[root@haproxy2:/etc/haproxy ]#

b) Restart haproxy-customname

[root@haproxy2:/usr/lib/systemd/system ]# systemctl restart haproxy-customname
[root@haproxy2:/usr/lib/systemd/system ]#

c) Check status is active running and process is properly forked

[root@haproxy2:/usr/lib/systemd/system ]# systemctl status haproxy-customname
● haproxy-customname.service – HAProxy Load Balancer
     Loaded: loaded (/lib/systemd/system/haproxy-customname.service; disabled; vendor preset: enabled)
     Active: active (running) since Tue 2022-08-30 13:15:35 EEST; 16s ago
       Docs: man:haproxy(1)
    Process: 346635 ExecStartPre=/usr/sbin/haproxy-customname-wrapper -f $CONFIG -c -q $EXTRAOPTS (code=exited, status=0/SUCCES>
   Main PID: 346637 (haproxy-customn)
      Tasks: 3 (limit: 4654)
     Memory: 14.5M
        CPU: 68ms
     CGroup: /system.slice/haproxy-customname.service
             ├─346637 /usr/sbin/haproxy-customname-wrapper -Ws -f /etc/haproxy/haproxy_customname_prod.cfg -p /run/haproxy_cust>
             └─346639 /usr/sbin/haproxy-customname-wrapper -Ws -f /etc/haproxy/haproxy_customname_prod.cfg -p /run/haproxy_cust>

Aug 30 13:15:35 haproxy2 haproxy-customname-wrapper[346637]:    | timeouts are set to a non-zero value: 'client', 'connect', 's>
Aug 30 13:15:35 haproxy2 haproxy-customname-wrapper[346637]: [NOTICE] 241/131535 (346637) : New worker #1 (346639) forked
Aug 30 13:15:35 haproxy2 haproxy-customname-wrapper[346637]: Proxy webservers_http started.
Aug 30 13:15:35 haproxy2 haproxy-customname-wrapper[346637]: Proxy webservers_http started.
Aug 30 13:15:35 haproxy2 haproxy-customname-wrapper[346637]: Proxy https-in started.
Aug 30 13:15:35 haproxy2 haproxy-customname-wrapper[346637]: Proxy https-in started.
Aug 30 13:15:35 haproxy2 haproxy-customname-wrapper[346637]: Proxy webservers-https started.
Aug 30 13:15:35 haproxy2 haproxy-customname-wrapper[346637]: Proxy webservers-https started.
Aug 30 13:15:35 haproxy2 haproxy-customname-wrapper[346637]: Proxy stats started.
Aug 30 13:15:35 haproxy2 haproxy-customname-wrapper[346637]: Proxy stats started.

The new haproxy-customname.service processes will be visible in process list together with the normal haproxy.service spawned processes:

[root@haproxy2:/usr/lib/systemd/system ]# ps -ef|grep -i hapro|grep -v grep
root      128464       1  0 Aug11 ?        00:01:19 /usr/sbin/haproxy -Ws -f /etc/haproxy/haproxy.cfg -p /run/ -S /run/haproxy-master.sock
haproxy   128466  128464  0 Aug11 ?        00:49:29 /usr/sbin/haproxy -Ws -f /etc/haproxy/haproxy.cfg -p /run/ -S /run/haproxy-master.sock

root      346637       1  0 13:15 ?        00:00:00 /usr/sbin/haproxy-customname-wrapper -Ws -f /etc/haproxy/haproxy_customname_prod.cfg -p /run/ -S /run/haproxy-customname-master.sock
haproxy   346639  346637  0 13:15 ?        00:00:00 /usr/sbin/haproxy-customname-wrapper -Ws -f /etc/haproxy/haproxy_customname_prod.cfg -p /run/ -S /run/haproxy-customname-master.sock


Following the same steps you can create as many separate haproxy instances as you like, but you have to be cautious not to intermix the listener ports for frontends. There is always risk when you copy from the original /etc/haproxy/haproxy.cfg to /etc/haproxy/haproxy-whatever.cfg to forget to change the listen port addresses in new config. 
Also note, that you might have problems, if you exceeed the usual maximum number of ports  65535 by using a high port ranges in the listeneres and due to that your additional systemd instances might refuse to start.

If you need to create a multiple bunch of systemd separte instances and haproxy configurations you can write easily a small script in bash that does this steps automatically.
Hope this article helped someone. If so drop me a thanks email or do your appreatiation for my blog by supporting my patreon.

Cheers ! 🙂

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