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.TH pg2 3 "kernel 2.12.3" "Ericsson AB" "ERLANG MODULE DEFINITION"
.SH MODULE
pg2 \- Distributed Named Process Groups
.SH DESCRIPTION
.LP
This module implements process groups\&. The groups in this module differ from the groups in the module \fIpg\fR in several ways\&. In \fIpg\fR, each message is sent to all members in the group\&. In this module, each message may be sent to one, some, or all members\&.
.LP
A group of processes can be accessed by a common name\&. For example, if there is a group named \fIfoobar\fR, there can be a set of processes (which can be located on different nodes) which are all members of the group \fIfoobar\fR\&. There is no special functions for sending a message to the group\&. Instead, client functions should be written with the functions \fIget_members/1\fR and \fIget_local_members/1\fR to find out which processes are members of the group\&. Then the message can be sent to one or more members of the group\&.
.LP
If a member terminates, it is automatically removed from the group\&.
.SS Warning:
.LP
This module is used by the \fIdisk_log\fR 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\&.
.SH EXPORTS
.LP
.B
create(Name) -> void()
.br
.RS
.TP
Types
Name = term()
.br
.RE
.RS
.LP
Creates a new, empty process group\&. The group is globally visible on all nodes\&. If the group exists, nothing happens\&.
.RE
.LP
.B
delete(Name) -> void()
.br
.RS
.TP
Types
Name = term()
.br
.RE
.RS
.LP
Deletes a process group\&.
.RE
.LP
.B
get_closest_pid(Name) -> Pid | {error, Reason}
.br
.RS
.TP
Types
Name = term()
.br
Pid = pid()
.br
Reason = {no_process, Name} | {no_such_group, Name}
.br
.RE
.RS
.LP
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\&.
.RE
.LP
.B
get_members(Name) -> [Pid] | {error, Reason}
.br
.RS
.TP
Types
Name = term()
.br
Pid = pid()
.br
Reason = {no_such_group, Name}
.br
.RE
.RS
.LP
Returns all processes in the group \fIName\fR\&. This function should be used from within a client function that accesses the group\&. It is therefore optimized for speed\&.
.RE
.LP
.B
get_local_members(Name) -> [Pid] | {error, Reason}
.br
.RS
.TP
Types
Name = term()
.br
Pid = pid()
.br
Reason = {no_such_group, Name}
.br
.RE
.RS
.LP
Returns all processes running on the local node in the group \fIName\fR\&. This function should to be used from within a client function that accesses the group\&. It is therefore optimized for speed\&.
.RE
.LP
.B
join(Name, Pid) -> ok | {error, Reason}
.br
.RS
.TP
Types
Name = term()
.br
Pid = pid()
.br
Reason = {no_such_group, Name}
.br
.RE
.RS
.LP
Joins the process \fIPid\fR to the group \fIName\fR\&. A process can join a group several times; it must then leave the group the same number of times\&.
.RE
.LP
.B
leave(Name, Pid) -> ok | {error, Reason}
.br
.RS
.TP
Types
Name = term()
.br
Pid = pid()
.br
Reason = {no_such_group, Name}
.br
.RE
.RS
.LP
Makes the process \fIPid\fR leave the group \fIName\fR\&. If the process is not a member of the group, \fIok\fR is returned\&.
.RE
.LP
.B
which_groups() -> [Name]
.br
.RS
.TP
Types
Name = term()
.br
.RE
.RS
.LP
Returns a list of all known groups\&.
.RE
.LP
.B
start()
.br
.B
start_link() -> {ok, Pid} | {error, Reason}
.br
.RS
.TP
Types
Pid = pid()
.br
Reason = term()
.br
.RE
.RS
.LP
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 \fIkernel\fR for this\&.
.RE
.SH SEE ALSO
.LP
kernel(6), pg(3)
|
