pg2(3erl)						     Erlang Module Definition							 pg2(3erl)

NAME

       pg2 - Distributed Named Process Groups

DESCRIPTION

       This module implements process groups. The groups in this module differ from the groups in the module pg in several ways. In pg , each mes-
       sage is sent to all members in the group. In this module, each message may be sent to one, some, or all members.

       A group of processes can be accessed by a common name. For example, if there is a group named foobar , there can  be  a	set  of  processes
       (which  can be located on different nodes) which are all members of the group foobar . There are no special functions for sending a message
       to the group. Instead, client functions should be written with the functions get_members/1 and get_local_members/1 to find out  which  pro-
       cesses are members of the group. Then the message can be sent to one or more members of the group.

       If a member terminates, it is automatically removed from the group.

   Warning:
       This module is used by the disk_log module for managing distributed disk logs. The disk log names are used as group names, which means that
       some action may need to be taken to avoid name clashes.

EXPORTS

       create(Name) -> void()

	      Types  Name = term()

	      Creates a new, empty process group. The group is globally visible on all nodes. If the group exists, nothing happens.

       delete(Name) -> void()

	      Types  Name = term()

	      Deletes a process group.

       get_closest_pid(Name) -> Pid | {error, Reason}

	      Types  Name = term()
		     Pid = pid()
		     Reason = {no_process, Name} | {no_such_group, Name}

	      This is a useful dispatch function which can be used from client functions. It returns a process	on  the  local	node,  if  such  a
	      process exist. Otherwise, it chooses one randomly.

       get_members(Name) -> [Pid] | {error, Reason}

	      Types  Name = term()
		     Pid = pid()
		     Reason = {no_such_group, Name}

	      Returns  all processes in the group Name . This function should be used from within a client function that accesses the group. It is
	      therefore optimized for speed.

       get_local_members(Name) -> [Pid] | {error, Reason}

	      Types  Name = term()
		     Pid = pid()
		     Reason = {no_such_group, Name}

	      Returns all processes running on the local node in the group Name . This function should to be used from within  a  client  function
	      that accesses the group. It is therefore optimized for speed.

       join(Name, Pid) -> ok | {error, Reason}

	      Types  Name = term()
		     Pid = pid()
		     Reason = {no_such_group, Name}

	      Joins  the process Pid to the group Name . A process can join a group several times; it must then leave the group the same number of
	      times.

       leave(Name, Pid) -> ok | {error, Reason}

	      Types  Name = term()
		     Pid = pid()
		     Reason = {no_such_group, Name}

	      Makes the process Pid leave the group Name . If the process is not a member of the group, ok is returned.

       which_groups() -> [Name]

	      Types  Name = term()

	      Returns a list of all known groups.

       start()
       start_link() -> {ok, Pid} | {error, Reason}

	      Types  Pid = pid()
		     Reason = term()

	      Starts the pg2 server. Normally, the server does not need to be started explicitly, as it is started dynamically if  it  is  needed.
	      This  is useful during development, but in a target system the server should be started explicitly. Use configuration parameters for
	      kernel for this.

SEE ALSO

       kernel(7) , pg(3erl)

Ericsson AB							   kernel 2.14.3							 pg2(3erl)