thintalk

Thintalk is a thin RPC layer over different transport layers.

RPC is an acronyms for Remote procedure call, meaning that the protocol is a simple function request with function arguments, and the response will be arguments parsed to an callback. The result is you can call code on the server without transferee the entire function source code.

The benefits of thintalk compared to nowJS or dnode is that this is very thin resulting in minimal overhead. However the cost is that this module is not meant to be used in combination with none-node clients like browsers.

Features

• Simple RPC layer with minimal overhead.
• Same API independent of the transport layer.
• Extendable abstraction layer.

Installation

npm install thintalk

API documentation

The modules is required by using the following code:

var thintalk = require('thintalk');

The variable thintalk now contain a function, depending on how it is called a Listener or a Requester object is returned.

The listener

A Lisenter is return if the thintalk function was called with a object. The given object should contain all procedures there can be called by the requester. Note that you are not allowed to add or remove procedures later.

var listener = thintalk({
  add: function (a, b) {
    this.callback(a + b);
  }
});

Lisenter.listen

The lisenter object must listen on something. this is done by calling the .listen method. The first argument in the .listen method specify the layer the other arguments are send to the layer handler.

Note that you can call listen as many times as you want.

lisenter.listen('TCP', 4001);
lisenter.listen('TCP', 4002);
 
var child = require('child_process').fork('./child.js');
lisenter.listen('IPC', child);

Lisenter.close

To close the lisenter simply call .close, note that all layers will be closed.

Events

Any errors there might occurre should be emitted though the error event, if not then it is properly a bug.

lisenter.on('error', function (err) {
  throw err;
});

The listening is emitted when a new lisenter layer is assigned and it is ready to rescive requests.

lisenter.on('listening', function () {
  console.log('layer ready');
});

When a requester is connected to the lisenter object a connection event is emitted:

lisenter.on('connection', function () {
  console.log('requester connected');
});

When closeing the lisenter a close event is emitted when all layers are closed.

lisenter.on('close', function () {
  console.log('lisenter closed');
});

When a requester make a procedure request a request event is emitted when a result is found or an errors accoured.

lisenter.on('request', function (error, name, args, result) {
  console.log('The function ' + name + ' was called with the arguments ' + args.join(', '));
 
  if (error !== null) {
    console.log('But the function called failed:');
    console.error(error.stack);
  } else {
    console.log('the result was ' + result);
  }
});

The Requester

The thintalk function will return a Requester object when a function or no arguments is given.

As with the Lisenter there is no API diffrence between the diffrence layers you might use. However a Requester can only connect to one remote.

If a function was given it is called with a remote object as its only arguments. The remote object contain the procedures defined in the lisenter, however they are only wrappers there call the remote procedure. The last argument in the wrapper are a callback containing a result argument.

var requester = thintalk(function (remote) {
  remote.add(2, 4, function (result) {
    console.log(result); // 6
  });
});

You connect to the remote by using the .connect method. The API is the same with .listen the first argument specify the layer and the other arguments are send to the layer handler.

To connect to a port using the the TCP layer:

requester.connect('TCP', 4000);

To connect to a process using the IPC layer.

requester.connect('IPC', process);

Requester.close

To close the requester simply call .close.

requester.close();

Events

Any errors there might occurre should be emitted though the error event, if not then it is properly a bug.

requester.on('error', function (err) {
  throw err;
});

When calling .close from the requester or the attached lisenter a close event is emitted when the requester is closed.

requester.on('close', function () {
  console.log('requester closed');
});

After calling .connect a connect event is emitted when every this is setup. The event handler is called with the remote object there also was given in function when calling the thintalk method.

requester.on('connect', function (remote) {
  remote.add(2, 4, function (result) {
    console.log(result); // 6
  });
});

Writeing a layer interface

There are two buildin layers IPC and TCP, they work very diffrent but use the same API abstaction to create an RPC interface. You can find the layers in /lib/layers, they are highly documented and should be easy to follow.

The general pattern is that there are three exported constructor functions, there inherts from a abstraction object. You will find that there is a little diffrence between the buildin layer and user layers. The buildin layers require an internal core.js module however you should just require the thinktalk module. This module will exports ListenerAbstract, CommunicationAbstract and RequesterAbstract just as the core.js module.

You will also need to use the setLayer function, this takes 2 arguments the first is the layer name the second is export from the required user layer.

var layer = require('layer');
var thintalk = require('thintalk');
thintalk.setLayer('layer', layer);

You can the use lisenter.listen('layer', options ...) and requester.connect('layer', options ...) just as with the TCP and IPC layer.

License

The software is license under "MIT"

Copyright (c) 2012 Andreas Madsen

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.