The gproc application

The gproc application

Extended process dictionary.

Authors: Ulf Wiger (ulf.wiger@erlang-solutions.com), Joseph Wayne Norton (norton@geminimobile.com).

Extended process dictionary

Introduction

Gproc is a process dictionary for Erlang, which provides a number of useful features beyond what the built-in dictionary has:

• Use any term as a process alias

• Register a process under several aliases

• Non-unique properties can be registered simultaneously by many processes

• QLC and match specification interface for efficient queries on the dictionary

• Await registration, let's you wait until a process registers itself

• Atomically give away registered names and properties to another process

• Counters, and aggregated counters, which automatically maintain the total of all counters with a given name

• Global registry, with all the above functions applied to a network of nodes

An interesting application of gproc is building publish/subscribe patterns. Example:

subscribe(EventType) ->
    %% Gproc notation: {p, l, Name} means {(p)roperty, (l)ocal, Name}
    gproc:reg({p, l, {?MODULE, EventType}}).

notify(EventType, Msg) ->
    Key = {?MODULE, EventType},
    gproc:send({p, l, Key}, {self(), Key, Msg}).

Gproc has a QuickCheck test suite, covering a fairly large part of the local gproc functionality, although none of the global registry. It requires a commercial EQC license, but rebar is smart enough to detect whether EQC is available, and if it isn't, the code in gproc_eqc.erl will be "defined away".

There is also an eunit suite, covering the basic operations for local and global gproc.

Building Edoc

By default, ./rebar doc generates Github-flavored Markdown files.If you want to change this, remove the edoc_opts line from rebar.config.

Gproc was first introduced at the ACM SIGPLAN Erlang Workshop in Freiburg 2007 (Paper available here).

Modules

gproc

gproc_app

gproc_dist

gproc_init

gproc_lib

gproc_sup