3.7. Programs

In master-worker mode, it is possible to launch external binaries with the
master, these processes are called programs. These programs are launched and
managed the same way as the workers.
 
During a reload of HAProxy, those processes are dealing with the same
sequence as a worker:
 
  - the master is re-executed
  - the master sends a SIGUSR1 signal to the program
  - if "option start-on-reload" is not disabled, the master launches a new
    instance of the program
 
During a stop, or restart, a SIGTERM is sent to the programs.

program

This is a new program section, this section will create an instance <name>
which is visible in "show proc" on the master CLI. (See "9.4. Master CLI" in
the management guide).

command [arguments*]

Define the command to start with optional arguments. The command is looked
up in the current PATH if it does not include an absolute path. This is a
mandatory option of the program section. Arguments containing spaces must
be enclosed in quotes or double quotes or be prefixed by a backslash.

option start-on-reload

no option start-on-reload

Start (or not) a new instance of the program upon a reload of the master.
The default is to start a new instance. This option may only be used in a
program section.