Asyngular server

Minimal server module for Asyngular.

This is a stand-alone server module for Asyngular (SocketCluster with full async/await support). Asyngular's protocol is backwards compatible with the SocketCluster protocol.

Setting up

You will need to install both asyngular-server and asyngular-client (https://github.com/SocketCluster/asyngular-client).

To install this module:

npm install asyngular-server

Usage

You need to attach it to an existing Node.js http or https server (example):

const http = require('http');
const asyngularServer = require('asyngular-server');
 
let httpServer = http.createServer();
let agServer = asyngularServer.attach(httpServer);
 
(async () => {
  // Handle new inbound sockets.
  for await (let {socket} of agServer.listener('connection')) {
 
    (async () => {
      // Set up a loop to handle and respond to RPCs for a procedure.
      for await (let req of socket.procedure('customProc')) {
        if (req.data.bad) {
          let error = new Error('Server failed to execute the procedure');
          error.name = 'BadCustomError';
          req.error(error);
        } else {
          req.end('Success');
        }
      }
    })();
 
    (async () => {
      // Set up a loop to handle remote transmitted events.
      for await (let data of socket.receiver('customRemoteEvent')) {
        // ...
      }
    })();
 
  }
})();
 
httpServer.listen(8000);

For more detailed examples of how to use Asyngular, see test/integration.js. Also, see tests from the asyngular-client module.

Asyngular can work without the for-await-of loop; a while loop with await statements can be used instead. See https://github.com/SocketCluster/stream-demux#usage

Compatibility mode

For compatibility with existing SocketCluster clients, set the protocolVersion to 1 and make sure that the path matches your old client path:

let agServer = asyngularServer.attach(httpServer, {
  protocolVersion: 1,
  path: '/socketcluster/'
});

Running the tests

Clone this repo: git clone git@github.com:SocketCluster/asyngular-server.git
Navigate to project directory: cd asyngular-server
Install all dependencies: npm install
Run the tests: npm test

Benefits of async `Iterable` over `EventEmitter`

More readable: Code is written sequentially from top to bottom. It avoids event handler callback hell. It's also much easier to write and read complex integration test scenarios.
More succinct: Event streams can be easily chained, filtered and combined using a declarative syntax (e.g. using async generators).
More manageable: No need to remember to unbind listeners with removeListener(...); just break out of the for-await-of loop to stop consuming. This also encourages a more declarative style of coding which reduces the likelihood of memory leaks and unintended side effects.
Less error-prone: Each event/RPC/message can be processed sequentially in the same order that they were sent without missing any data; even if asynchronous calls are made inside middleware or listeners. On the other hand, with EventEmitter, the listener function for the same event cannot be prevented from running multiple times in parallel; also, asynchronous calls within middleware and listeners can affect the final order of actions; all this can cause unintended side effects.

License

(The MIT License)

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.