pg2(3)



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

NAME
       pg2 - Distributed named process groups.

DESCRIPTION
   Warning:
       The  pg2 module is deprecated as of OTP 23 and scheduled for removal in
       OTP 24. You are advised to replace the usage of pg2 with pg. pg  has  a
       similar  API, but with an implementation that is more scalable. See the
       documentation of pg for more information about differences.

       This module implements process groups. Each message can be sent to one,
       some, or all group 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) that are all members of the group
       foobar. There are no special functions for sending  a  message  to  the
       group.  Instead,  client functions are to be written with the functions
       get_members/1 and get_local_members/1 to determine which processes  are
       members of the group. Then the message can be sent to one or more group
       members.

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

   Warning:
       This module is used by module disk_log for  managing  distributed  disk
       logs. The disk log names are used as group names, which means that some
       action can be needed 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  visi-
              ble 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}

              A  useful  dispatch  function that can be used from client func-
              tions. It returns a process on the local node, if such a process
              exists. Otherwise, it selects one randomly.

       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 is to be used from within a client  function
              that accesses the group. It is therefore optimized for speed.

       get_members(Name) -> [pid()] | {error, {no_such_group, Name}}

              Types:

                 Name = name()

              Returns  all processes in the group Name. This function is 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 many times and 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.

       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  sys-
              tem  the  server is to be started explicitly. Use the configura-
              tion parameters for kernel(7) for this.

       which_groups() -> [Name :: name()]

              Returns a list of all known groups.

SEE ALSO
       kernel(7)

Ericsson AB                       kernel 7.0                         pg2(3erl)

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