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)