Develop services as single processes, deploy them as multiple.
Develop services as single processes and deploy them as multiple.
Let's write a webserver that stores and receives data from a leveldb, and operates on querystrings. Since we want to be able to split up the http server and the leveldb later, we give each a role:
var role = require'role';var level = require'level';var multilevel = require'multilevel';var http = require'http';var qs = require'querystring';// we define the `db` roleroleset'db'var db = level__dirname + '/db';returnreturn multilevelserverdb;;// we define the `main` roleroleset'main'var db = multilevelclient;// we request the `db` roleroleget'db'spipedbcreateRpcStreampipes;;httpcreateServervar query = qsparserequrlsplit'?'slice1join'';if querygetdbgetquerygetif err resend'not found';else resendval;;else if queryputdbputqueryput queryvalueif err resendStringerr;else resend'ok';;elseresend'try\n\n/?put=foo&value=bar\n\n/?get=foo';listen8000console.log'~> localhost:8000';;;
main is a special role which will always be executed immediately. All the
other rules will be executed when requested via
Now, to start as a single process:
$ node example/simple.js$ open
To start as two seperate processes:
$ HUB=7888 ROLE=main node example/simple.js$ CLIENT=7888 ROLE=db node example/simple.js
To start as three seperate processes (mind synchronisation):
$ HUB=7888 ROLE=main node example/simple.js$ CLIENT=7888 ROLE=db node example/simple.js$ CLIENT=7888 ROLE=db node example/simple.js$ # Now you can just kill and recreate one database at a time and the sitewill stay up.
When using distributed/production mode you just have to make sure that there's always have at least one hub running.
fn with a stream for role
name. When the connection is lost and a new
one is made or already available, call
fn to be role
fn should return a Stream or a Function
that returns a Stream.
Pass none for local mode. Pass
HUB: Be a hub and listen on that port.
CLIENT: Be a client and listen on that port.
ROLE: The role to serve. Multiple roles are activated when you pass a comma-seperated list, like
With npm do
$ npm install role
Copyright (c) 2013 Julian Gruber <firstname.lastname@example.org>
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