pg2(3erl)

NAME

   pg2 - Distributed named process groups.

DESCRIPTION

   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
          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}

          A  useful  dispatch  function  that  can  be  used  from  client
          functions.  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
          system  the  server  is  to  be  started  explicitly.  Use   the
          configuration parameters for kernel(7) for this.

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

          Returns a list of all known groups.

SEE ALSO

   kernel(7)

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