Pogostick Http

This is the implementation of the Pogostick protocol for http.

Introductory Example

// Use whichever promise library you want, as long as it follows Promises/A+ 
// spec.
var Promise = require('bluebird');
var pogo = require('pogostick-http');
var mkServer = pogo.server({
	host: 'localhost'	
});

var server = mkServer({
	add: function(a, b) {
		return 1 + 2;
	},
	// You can also return promises and it will return only the result contained
	// within it. If the promise is rejected, it will also be rejected on the 
	// client.
	delayedGreet: function(name) {
		return new Promise(function(resolve) {
			setTimeout(function() { 
				resolve('hello world!');
			}, 5000);
		});
});

// you need to pass to the client constructor a function which generates
// promise instances.
var promiseFactory = function(resolver) { return new Promise(resolver); };
var mkClient = pogo.client(promiseFactory, { host: 'localhost' });

server.listen(3000, function() {
	mkClient({ port: 3000 }, function(err, remote) {
		Promise.all([
			remote.add(1, 2),
			remote.delayedGreet()
		]).spread(function(sum, greet) {
			console.log(sum, greet);
		});
	});
});

Features

Deep Objects

Pogostick supports using objects as namespaces. It also supports arrays of functions.

// Server
var server = mkServer({
	foo: {
		bar: function() {
			return "foobar";
		},
		baz: function() {
			return "foobaz";
		}
	}
});
// etc...

// Client
mkClient({ port: 3000 }, function(err, remote) {
	remote.foo.bar().then(function(res) {
		console.log('server says: ', res); // -> server says: foobar
	});
});

Pick-Your-Own Promises

As long as the library you choose follows the Promises/A+ specification, you can use your favourite promises library. You just need to specify the factory function so that pogostick can instantiate the promises for you.

var Bluebird = require('bluebird');
var bluebirdMkClient = pogo.client(function(resolver) {
	return new Bluebird(resolver);
});

var Q = require('q');
var qMkClient = pogo.client(Q.Promise);

var when = require('when');
var whenMkClient = pogo.client(when.promise);

Implicit Parameters

Implicit parameters in Pogostick are inspired by Scala implicit parameters. These were implemented to make it possible to pass authentication tokens and such into remote procedures without having to specify them every time. So, here's an example:

Server:

...
mkServer({
	greet: function() {
		// You access the implicit values sent by the client through the "this"
		// keyword.
		return "hello " + this.name + "!";
	}
});
...

Client:

mkClient({ port: 3000 }, function(err, remote) {
	if(err) return console.log('there was an error loading the remote');
	var withName = remote.$implicitly('name', 'AGhost-7');
	// Using withName, you will automatically send "AGhost-7" to the server.
	withName
		.greet()
		.then(console.log.bind(console));
});

The client in this case will print to the console Hello AGhost-7.

Module Types

promiseFactory is a function which accepts a resolver function and returns a promise. It is bundled in most promise libaries and can usually be easily created when it is not.

var fs = require('fs');
var Q = require('q');
var p = Q.promise(function(resolve, reject) {
	fs.readFile('/etc/dkms', function(err, buf) {
		err ? reject(err) : resolve(buf.toString());
	});
});
p.then(console.log.bind(console));

The Remote Object

The remote object contains all procedures that the server has listed, allowing you to call the functions from the network. There are two additional methods which are added to the remote object.

$end()

Prevents the procedures on the remote from sending any more requests to the server. This is called internally in some cases.

// returns a resolved promise if there was no error
remote.foo(); 
// Close the remote
remote.$end();
// skips fetching to the server and will just return a rejected promise
remote.foo();

$implicitly([dynamnic])

Returns a new remote instance which will send the data to the server each time you call the procedures on it.

Use it like a map containing automatically sent pieces of data.

var withName = remote.$implicitly('name', 'AGhost-7');
withName.greet(); // -> name is "AGhost-7"

You can create a new remote with the value at the specified key of removed.

var noName = withName.$implicitly('name');
noName.greet(); // -> name is undefined

Transfer properties on objects to the implicit context.

var withContext = noName.$implicitly({
	name: 'foobar',
	gameScore: 5000
});
withContext.greet(); // -> name is "foobar", and gameScore is 5000.

Transfer specific properties from an object to the implicit context.

var withContext = noName.$implicitly({
	name: 'foobar',
	gameScore: 5000,
	level: 5,
	experience: 34908725
}, 'name', 'level');
// -> sends only send the name and level property from the implicit context.
withContext.greet();

$implicitlyMut(key[, value])

Modifies the implicit context on the remote, mutating it. Delete the value from the context by not specifying the value argument.

Client Events

error

The error event is triggered whenever the client receives and err message back from the server. Essentially, whenever the remote object returns a rejected promise.

This can be useful if you want to catch certain connection errors. For example, you may want to give GUI feedback if you can't connect to the server because there is no connection.

exit

This is a response that the server can send to the client to terminate any more requests. This will cause the remote to stop sending requests, and simply return rejected promises every time.

end

Called at any time the remote is no longer capable of sending requests. For the http implementations, this is only the case when the server sends a exit response. For persistent connections such as TCP, the end event is triggered whenever the connection is lost as well.

Module Functions

client(promiseFactory)

Returns a client generating function that you can pass an options object and a complete handler to.

The options are passed to the underlying native nodeJS http module, giving the options such as port and host.

You also have access to the on option, which alows you to specify event handlers.

https.client(promiseFactory)

Returns a client generating function similar to client(promiseFactory). Just like client(promiseFactory), the options are passed to the underlying native nodeJs module, this time https. There is also the on option, which list events you can listen to.

var mkClient = pogo.client(promise);
var options = {
	host: 'localhost',
	port: 3000,
	on: {
		end: function() {
			console.log('Connection was ended');
		},
		error: function(err) {
			if(err.code === 'ECONNREFUSED') {
				console.log('could not connect to server!');
			}
		}
	}
};

mkClient(options, function(err, remote) {
	...
});

server(options)

Accepts the default options and returns a server instantiation function. Each server instance will inherit the inital options specified in the function.

The options are the following:

• headers specifies which headers to send out in each request.

server.fn(options, procs)

Function accepts an options object just like server(options) and a object containing the functions that the client will be able to call.

It will return a request handling function which accepts a http.IncomingMessage and a http.ServerResponse.

https.server(options)

Similar to server(options with two additional options.

• cert, the ssl certificate.
• key, which is the encryption key.

https.server.fn(options, procs)

Identical to server.fn(options, procs) with the only difference being this is for the stock https module.

exit([message])

This tells the client that the server is no longer available. The client implementation will stop its connection and the remotes will no longer send requests, only returning rejected promises. Triggers the end and exit event.

var pogo = require('pogostick-http');
...
mkServer({
	divide: function(a, b) {
		if(b === 0) {
			// The `message` argument is optional.
			return pogo.exit();
		} else {
			return a / b;
		}
	}
});
...

Example Uses

Express.js

var pogo = require('pogostick-http');
var express = require('express');
var app = express();

var procedures = {
	add: function(a, b){ 
		return a + b;
	}
};

var handler = pogo.server.fn({}, procedures);

// Add a middleware to serve up rpc calls.
app.use('/rpc', function(req, res, next) {
	hander(req, res);
});

app.use(express.static('/public'));

...