gproc 0.6.1

Extended process registry for Erlang

Platform: Hex

Language: Erlang

License: EPL-1.0


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The gproc application

Authors: Ulf Wiger ([email protected]), Joseph Wayne Norton ([email protected]).

Extended process dictionary

Build Status Hex pm


Gproc has two dependencies: gen_leader and edown. Since most people don't actively use either, they are no longer fetched by default.

  • To enable fetching of gen_leader, export the OS environment variableGPROC_DIST=true (this can be done e.g. from a GNU Makefile)

  • edown is fetched on-demand whenever rebar get-deps doc is called (which happens when you call make doc)


You can get gproc from the Hex package manager

That means declaring dependency on {gproc, "0.5.0"} in your rebar3-based applications or {:gproc, "~> 0.5.0"} in your mix based applications.


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

Use case: System inspection

Gproc was designed to work as a central index for "process metadata", i.e. properties that describe the role and characteristics of each process. Having a single registry that is flexible enough to hold important types of property makes it easier to (a) find processes of a certain type, and (b) query and browse key data in a running system.

Use case: Pub/Sub patterns

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}).

Use case: Environment handling

Gproc provides a set of functions to read environment variables, possibly from alternative sources, and cache them for efficient lookup. Caching also provides a way to see which processes rely on certain configuration values, as well as which values they actually ended up using.

See gproc:get_env/4, gproc:get_set_env/4 and gproc:set_env/5 for details.


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).




  • 0.6.1 - September 03, 2016 23:11
  • 0.5.0 - September 15, 2015 11:20
  • 0.3.1 - August 12, 2014 17:04
  • 0.3.0 - August 11, 2014 18:06

Project Statistics

SourceRank 16
Dependencies 0
Dependent projects 22
Dependent repositories 75
Total releases 4
Latest release
First release
Stars 701
Forks 172
Watchers 65
Contributors 26
Repo Size: 2.04 MB

Top Contributors See all

Ulf Wiger Joseph Wayne Norton Stefan Grundmann Remigiusz Jackowski Bhasker Kode Daniel Luna Yuriy Bogdanov Martin Schürrer Klas Johansson Luca Favatella Dmitry Demeshchuk Matt Campbell Peter Lemenkov Sergey Loguntsov Tino Breddin Torben Hoffmann benbro Byaruhanga Franklin Michał Muskała Uģis Ozols

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