Dualapi NPM | npm.io

DualAPI

A lightweight and extensible framework for distributed isomorphic javascript applications. DualAPI extends dual-protocol, adding convenience functions and default behaviors for common messaging patterns.

For a simple example distributed example, see the dual-engine.io example.

Constructing domains

The dualapi module is the constructor for dualapi domains.

  var d = require('dualapi')();

The most common use case for dualapi domains is to provide a listener function for processing dual-protocol messages. Hosts are attached to the domain by using the dual-protocol mount method:

  d.mount(['unresponsive'], function (body, ctxt) {
    // do some processing
  });

Request and Return

Often, a dualapi host will emit a response after processing input. dualapi provides a convienent extension to dual-protocol by providing the ctxt.return method.

  d.mount(['simpledb', 'get'], function (body, ctxt) {
    ctxt.return('the processed response');
  });

By default, return sets the returned options.statusCode to 200. Then, any method having access to a connected domain may request data from this address. The request method returns a spreadable promise which will be resolved when the source host replies:

  d.request(['simpledb', 'get'])
    .spread(function (body, options) {
       console.log(options.statusCode + ' ' + body);
    });

   // prints:
   // "200 the processed response"

A smarter database can override the response statusCode by providing explicit options.

  var db = {};
  d.mount(['smarterdb', 'set', ':key'], function (body, ctxt) {
    if (db.hasOwnProperty(ctxt.params.key)) {
       ctxt.return('Conflict', { statusCode: 409 });
    } else {
       db[ctxt.params.key] = body;
       ctxt.return('OK', { statusCode: 201 });
    }
  });

  d.mount(['smarterdb', 'get', ':key'], function (body, ctxt) {
    if (db.hasOwnProperty(ctxt.params.key)) {
       ctxt.return(db[ctxt.params.key]);
    } else {
       ctxt.return('Not Found', { statusCode: 404 });
    }
  });

A client can use the enhanced status codes to modify its own response:

  d.request(['smarterdb', 'get', 'bucket'])
      .spread(function (body, options) {
         if (options.statusCode == 200) {
            console.log('' + options.statusCode + ' Request returned: ' + body);
         } else {
            console.log('' + options.statusCode + ' Failed to retrieve from bucket.');
         }
      });
      
  d.request(['smarterdb', 'set', 'bucket'], 'an egg')
      .spread(function (body, options) {
         if (options.statusCode == 201) {
            console.log('' + options.statusCode + ' Wrote to bucket');
         } else {
            console.log('' + options.statusCode + ' Failed to write to bucket.');
         }
      });

  d.request(['smarterdb', 'get', 'bucket'])
      .spread(function (body, options) {
         if (options.statusCode == 200) {
            console.log('' + options.statusCode + ' Second request got: ' + body);
         } else {
            console.log('' + options.statusCode + ' Second request failed to retrieve bucket.');
         }
      });

  // Running this the first time would print:
  // 404 Failed to retrieve from bucket
  // 201 Wrote to bucket
  // 200 Second request got: an egg

  // Running a second time would print:
  // 200 Request returned: an egg
  // 409 Failed to write to bucket.
  // 200 Second request got: an egg

On the other hand, if no host is listening at the requested address, request will return with a status code of 503. The request may also provide a timeout option, in which case the status code will be 504.

d.request(['nowhere'])
    .spread(function (body, options) {
        console.log('"nowhere" request returned status code ' + options.statusCode);
    });

// would print
// "nowhere" request returned status code 503

d.request(['unresponsive'], null, { timeout: 1 })
    .spread(function (body, options) {
        console.log('"unresponsive" request returned status code ' + options.statusCode);
    });

// would print (after 1 second delay)
// "unresponsive" request returned status code 504