Node DDP Client

A callback style DDP (Meteor's Distributed Data Protocol) node client, originally based alansikora's node-js_ddp-client and Meteor's python client. Uses a more callback style approach.

The client implements version 1 of DDP, as well as fallbacks to pre1 and pre2.

Installation

  npm install ddp

Authentication

Built-in authentication support was removed in ddp 0.7.0 due to changes in Meteor version 0.8.2.

DDP Authentication is now implemented by vsivsi/ddp-login.

A quick and dirty (but insecure) alternative is to use plain-text logins via a method call:

// logging in with e-mail
ddpclient.call("login", [
  { user : { email : "user@domain.com" }, password : "password" }
], function (err, result) { ... });

// logging in with username
ddpclient.call("login", [
  { user : { username : "username" }, password : "password" }
], function (err, result) { ... });

Example

Please see the example in examples/example.js. Or here for reference:

var DDPClient = require("ddp");

var ddpclient = new DDPClient({
  // All properties optional, defaults shown
  host : "localhost",
  port : 3000,
  ssl  : false,
  autoReconnect : true,
  autoReconnectTimer : 500,
  maintainCollections : true,
  ddpVersion : '1',  // ['1', 'pre2', 'pre1'] available
  // uses the SockJs protocol to create the connection
  // this still uses websockets, but allows to get the benefits
  // from projects like meteorhacks:cluster
  // (for load balancing and service discovery)
  // do not use `path` option when you are using useSockJs
  useSockJs: true,
  // Use a full url instead of a set of `host`, `port` and `ssl`
  // do not set `useSockJs` option if `url` is used
  url: 'wss://example.com/websocket'
});

/*
 * Connect to the Meteor Server
 */
ddpclient.connect(function(error, wasReconnect) {
  // If autoReconnect is true, this callback will be invoked each time
  // a server connection is re-established
  if (error) {
    console.log('DDP connection error!');
    return;
  }

  if (wasReconnect) {
    console.log('Reestablishment of a connection.');
  }

  console.log('connected!');

  setTimeout(function () {
    /*
     * Call a Meteor Method
     */
    ddpclient.call(
      'deletePosts',             // name of Meteor Method being called
      ['foo', 'bar'],            // parameters to send to Meteor Method
      function (err, result) {   // callback which returns the method call results
        console.log('called function, result: ' + result);
      },
      function () {              // callback which fires when server has finished
        console.log('updated');  // sending any updated documents as a result of
        console.log(ddpclient.collections.posts);  // calling this method
      }
    );
  }, 3000);

  /*
   * Call a Meteor Method while passing in a random seed.
   * Added in DDP pre2, the random seed will be used on the server to generate
   * repeatable IDs. This allows the same id to be generated on the client and server
   */
  var Random = require("ddp-random"),
      random = Random.createWithSeeds("randomSeed");  // seed an id generator

  ddpclient.callWithRandomSeed(
    'createPost',              // name of Meteor Method being called
    [{ _id : random.id(),      // generate the id on the client
      body : "asdf" }],
    "randomSeed",              // pass the same seed to the server
    function (err, result) {   // callback which returns the method call results
      console.log('called function, result: ' + result);
    },
    function () {              // callback which fires when server has finished
      console.log('updated');  // sending any updated documents as a result of
      console.log(ddpclient.collections.posts);  // calling this method
    }
  );

  /*
   * Subscribe to a Meteor Collection
   */
  ddpclient.subscribe(
    'posts',                  // name of Meteor Publish function to subscribe to
    [],                       // any parameters used by the Publish function
    function () {             // callback when the subscription is complete
      console.log('posts complete:');
      console.log(ddpclient.collections.posts);
    }
  );

  /*
   * Observe a collection.
   */
  var observer = ddpclient.observe("posts");
  observer.added = function(id) {
    console.log("[ADDED] to " + observer.name + ":  " + id);
  };
  observer.changed = function(id, oldFields, clearedFields, newFields) {
    console.log("[CHANGED] in " + observer.name + ":  " + id);
    console.log("[CHANGED] old field values: ", oldFields);
    console.log("[CHANGED] cleared fields: ", clearedFields);
    console.log("[CHANGED] new fields: ", newFields);
  };
  observer.removed = function(id, oldValue) {
    console.log("[REMOVED] in " + observer.name + ":  " + id);
    console.log("[REMOVED] previous value: ", oldValue);
  };
  setTimeout(function() { observer.stop() }, 6000);
});

/*
 * Useful for debugging and learning the ddp protocol
 */
ddpclient.on('message', function (msg) {
  console.log("ddp message: " + msg);
});

/*
 * Close the ddp connection. This will close the socket, removing it
 * from the event-loop, allowing your application to terminate gracefully
 */
ddpclient.close();

/*
 * If you need to do something specific on close or errors.
 * You can also disable autoReconnect and
 * call ddpclient.connect() when you are ready to re-connect.
*/
ddpclient.on('socket-close', function(code, message) {
  console.log("Close: %s %s", code, message);
});

ddpclient.on('socket-error', function(error) {
  console.log("Error: %j", error);
});

/*
 * You can access the EJSON object used by ddp.
 */
var oid = new ddpclient.EJSON.ObjectID();

SockJS Mode

By using the useSockJs option like below, DDP connection will use SockJs protocol to establish the WebSocket connection.

var ddpClient = new DDPClient({ useSockJs: true });

Meteor server uses SockJs to implement it's DDP server. With this mode, we can get the benefits provided by meteorhacks:cluster. Some of those are load balancing and service discovery.

• For load balancing you don't need to anything.
• For service discovery, just use the path option to identify the service you are referring to.

With this mode, path option has a special meaning. So, thing twice before using path option when you are using this option.

Unimplemented Features

The node DDP client does not implement ordered collections, something that while in the DDP spec has not been implemented in Meteor yet.

Thanks

Many thanks to Alan Sikora for the ddp-client which formed the inspiration for this code.

Contributions:

• Tom Coleman (@tmeasday)
• Thomas Sarlandie (@sarfata)
• Mason Gravitt (@emgee3)
• Mike Bannister (@possiblities)
• Chris Mather (@eventedmind)
• James Gill (@jagill)
• Vaughn Iverson (@vsivsi)