NAME

       pg2 - Distributed Named Process Groups

DESCRIPTION

       This  module  implements  process  groups.  Each  message may be sent to one, some, or all members of the
       group.

       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
       processes 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.

DATA TYPES

       name() = any()

              The name of a process group.

EXPORTS

       create(Name :: name()) -> ok

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

       delete(Name :: name()) -> ok

              Deletes a process group.

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

              Types:

                 Name = name()
                 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, {no_such_group, Name}}

              Types:

                 Name = 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, {no_such_group, Name}}

              Types:

                 Name = 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 :: pid()) -> ok | {error, {no_such_group, Name}}

              Types:

                 Name = 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 :: pid()) -> ok | {error, {no_such_group, Name}}

              Types:

                 Name = 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 :: name()]

              Returns a list of all known groups.

       start() -> {ok, pid()} | {error, any()}

       start_link() -> {ok, pid()} | {error, any()}

              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)