Comment 2 for bug 1774765

Thanks for filing this bug in Ubuntu.

This is the error log:
Setting up haproxy (1.8.8-1ubuntu0.1) ...
Job for haproxy.service failed because the control process exited with error code.
See "systemctl status haproxy.service" and "journalctl -xe" for details.
invoke-rc.d: initscript haproxy, action "start" failed.
● haproxy.service - HAProxy Load Balancer
   Loaded: loaded (/lib/systemd/system/haproxy.service; enabled; vendor preset: enabled)
   Active: activating (auto-restart) (Result: exit-code) since Sat 2018-06-02 12:55:58 IST; 5ms ago
     Docs: man:haproxy(1)
           file:/usr/share/doc/haproxy/configuration.txt.gz
  Process: 6482 ExecStart=/usr/sbin/haproxy -Ws -f $CONFIG -p $PIDFILE $EXTRAOPTS (code=exited, status=1/FAILURE)
  Process: 6481 ExecStartPre=/usr/sbin/haproxy -f $CONFIG -c -q $EXTRAOPTS (code=exited, status=0/SUCCESS)
 Main PID: 6482 (code=exited, status=1/FAILURE)

Jun 02 12:55:59 Dell haproxy[6495]: [ALERT] 152/125559 (6495) : Starting proxy mysql: cannot bind socket [127.0.0.1:3306]
Jun 02 12:55:59 Dell systemd[1]: haproxy.service: Main process exited, code=exited, status=1/FAILURE
Jun 02 12:55:59 Dell systemd[1]: haproxy.service: Failed with result 'exit-code'.
Jun 02 12:55:59 Dell systemd[1]: Failed to start HAProxy Load Balancer.
Jun 02 12:55:59 Dell systemd[1]: haproxy.service: Service hold-off time over, scheduling restart.
Jun 02 12:55:59 Dell systemd[1]: haproxy.service: Scheduled restart job, restart counter is at 5.
Jun 02 12:55:59 Dell systemd[1]: Stopped HAProxy Load Balancer.
Jun 02 12:55:59 Dell systemd[1]: haproxy.service: Start request repeated too quickly.
Jun 02 12:55:59 Dell systemd[1]: haproxy.service: Failed with result 'exit-code'.
Jun 02 12:55:59 Dell systemd[1]: [0;

It looks like you have another service already listening on port 3306. Perhaps it's mysql itself?

Please attach these files:
/etc/default/haproxy
/etc/haproxy/haproxy.cfg

And show the output of this command:
sudo netstat -anp

Thanks!