trusty (3) pg2.3erl.gz

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 message 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
       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), pg(3erl)