ddp

Node.js module to connect to servers using DDP protocol.

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.

One can authenticate using plain-text logins as follows:

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

You can also use vsivsi/ddp-login.

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
});
 
/*
 * Connect to the Meteor Server
 */
ddpclient.connect(function(errorwasReconnect) {
  // 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 (errresult) {   // 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 (errresult) {   // 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(idoldFieldsclearedFieldsnewFields) {
    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(idoldValue) {
    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(codemessage) {
  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)