Extended process dictionary.
Authors: Ulf Wiger ([email protected]
), Joseph Wayne Norton ([email protected]
).
Extended process dictionary
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
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.
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 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.
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).
gproc |
gproc_app |
gproc_dist |
gproc_init |
gproc_lib |
gproc_sup |