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)