While starting haproxy with command #systemctl restart/start haproxy in centos…haproxy-systemd-wrapper spawns haproxy twice. Why it is so? Does it for multiprocessor programming?
The systemd-wrapper spawns the master process which then spawns an actual child process. So yes, when haproxy is running in “single” process mode, there are actually 3 processes.
Note that in 1.8 we got rid of the systemd-wrapper, and we only have master -> child process left.
So what is use of another haproxy child process. Does this work same things, as another is doing.
The child process does the actual forwarding of traffic, the master process just manages the processes.
When you are not using multiprocess mode (nbproc), there is just 1 child process.
If you have nbproc 4 for example, you have 4 child processes.