gproc/doc/overview.edoc

@author Ulf Wiger <ulf.wiger@erlang-solutions.com>
@author Joseph Wayne Norton <norton@geminimobile.com>

@doc 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:

<ul>
<li>Use any term as a process alias</li>
<li>Register a process under several aliases</li>
<li>Non-unique properties can be registered simultaneously by many processes</li>
<li>QLC and match specification interface for efficient queries on the 
  dictionary</li>
<li>Await registration, let's you wait until a process registers itself</li>
<li>Atomically give away registered names and properties to another process</li>
<li>Counters, and aggregated counters, which automatically maintain the 
  total of all counters with a given name</li>
<li>Global registry, with all the above functions applied to a network of nodes</li>
</ul>

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

<pre>
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}).
</pre>

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 (<a href="erlang07-wiger.pdf">Paper available here</a>).

@end