Develop services as single processes, deploy them as multiple.
Develop services as single processes, deploy them as multiple - from a single code base.
Each service is a
role and exports a stream, as every good networker does.
Then cluster / distributed roles as you wish.
Network partitions / reconnects are handled transparently.
Let's write a CLI app that uppercases
stdin. Because in production we'll want
to use multiple processes and especially split up uppercasing from the
frontend, we use a role for each:
var role = require'role';var through = require'through';role'uppercaser'return throughthisqueuechunktoStringtoUpperCase;;;role'main'rolesubscribe'uppercaser'processstdinpipethrough thisqueuectoStringpipeupperpipeprocessstdout;;;
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/uppercaser.jshiHIwhat's upWHAT'S UP
To start as two seperate processes, one being the uppercaser (read: doing something cpu intensive), the other being being the frontend:
$ HUB=7888 ROLE=main node example/uppercaser.js$ CLIENT=7888 ROLE=uppercaser node example/uppercaser.js
To start as three seperate processes:
$ HUB=7888 ROLE=main node example/uppercaser.js$ CLIENT=7888 ROLE=uppercaser node example/uppercaser.js$ CLIENT=7888 ROLE=uppercaser node example/uppercaser.js$ # you can kill any client without causing downtime
When using distributed / production mode just make sure that there's always at least one hub running.
When you only need a stream once,
role.get(name) returns a stream that you can use immediately and buffers if necessary:
var role = require'..';var through = require'through';role'uppercaser'return throughthisqueuechunktoStringtoUpperCase;;;role'main'processstdinsetEncoding'utf8';processstdinpiperoleget'uppercaser'pipeprocessstdout;;
fn to be role
fn should return a Stream or a Function
that returns a Stream.
Return a Stream that can be used immediately and if necessary buffers until the connection is made.
fn with a stream for role
name. When the connection is lost and a new
one is made or already available, call
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
DEBUG=role to see what's going on:
With npm do
$ npm install role
Copyright (c) 2013 Julian Gruber <firstname.lastname@example.org>
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