.TH pg 3erl "stdlib 2.2" "Ericsson AB" "Erlang Module Definition"
.SH NAME
pg \- Distributed, Named Process Groups
.SH DESCRIPTION
.LP

.RS -4
.B
Warning:
.RE
This module is deprecated and will be removed in Erlang/OTP 18\&.

.LP
This (experimental) module implements process groups\&. A process group is a group of processes that can be accessed by a common name\&. For example, a group named \fIfoobar\fR\& can include a set of processes as members of this group and they can be located on different nodes\&.
.LP
When messages are sent to the named group, all members of the group receive the message\&. The messages are serialized\&. If the process \fIP1\fR\& sends the message \fIM1\fR\& to the group, and process \fIP2\fR\& simultaneously sends message \fIM2\fR\&, then all members of the group receive the two messages in the same order\&. If members of a group terminate, they are automatically removed from the group\&.
.LP
This module is not complete\&. The module is inspired by the ISIS system and the causal order protocol of the ISIS system should also be implemented\&. At the moment, all messages are serialized by sending them through a group master process\&.
.SH EXPORTS
.LP
.nf

.B
create(PgName) -> ok | {error, Reason}
.br
.fi
.br
.RS
.LP
Types:

.RS 3
PgName = term()
.br
Reason = already_created | term()
.br
.RE
.RE
.RS
.LP
Creates an empty group named \fIPgName\fR\& on the current node\&.
.RE

.LP
.nf

.B
create(PgName, Node) -> ok | {error, Reason}
.br
.fi
.br
.RS
.LP
Types:

.RS 3
PgName = term()
.br
Node = node()
.br
Reason = already_created | term()
.br
.RE
.RE
.RS
.LP
Creates an empty group named \fIPgName\fR\& on the node \fINode\fR\&\&.
.RE

.LP
.nf

.B
join(PgName, Pid) -> Members
.br
.fi
.br
.RS
.LP
Types:

.RS 3
PgName = term()
.br
Pid = pid()
.br
Members = [pid()]
.br
.RE
.RE
.RS
.LP
Joins the pid \fIPid\fR\& to the process group \fIPgName\fR\&\&. Returns a list of all old members of the group\&.
.RE

.LP
.nf

.B
send(PgName, Msg) -> ok
.br
.fi
.br
.RS
.LP
Types:

.RS 3
PgName = Msg = term()
.br
.RE
.RE
.RS
.LP
Sends the tuple \fI{pg_message, From, PgName, Msg}\fR\& to all members of the process group \fIPgName\fR\&\&.
.LP
Failure: \fI{badarg, {PgName, Msg}}\fR\& if \fIPgName\fR\& is not a process group (a globally registered name)\&.
.RE

.LP
.nf

.B
esend(PgName, Msg) -> ok
.br
.fi
.br
.RS
.LP
Types:

.RS 3
PgName = Msg = term()
.br
.RE
.RE
.RS
.LP
Sends the tuple \fI{pg_message, From, PgName, Msg}\fR\& to all members of the process group \fIPgName\fR\&, except ourselves\&.
.LP
Failure: \fI{badarg, {PgName, Msg}}\fR\& if \fIPgName\fR\& is not a process group (a globally registered name)\&.
.RE

.LP
.nf

.B
members(PgName) -> Members
.br
.fi
.br
.RS
.LP
Types:

.RS 3
PgName = term()
.br
Members = [pid()]
.br
.RE
.RE
.RS
.LP
Returns a list of all members of the process group \fIPgName\fR\&\&.
.RE