pubsub: default autoCreate:true

Author: stephenplusplus

README.md

@@ -214,13 +214,11 @@ var pubsub = gcloud.pubsub({
   keyFilename: '/path/to/keyfile.json'
 });
 
-// Create a new topic.
-pubsub.createTopic('my-new-topic', function(err, topic) {});
-
-// Reference an existing topic.
-var topic = pubsub.topic('my-existing-topic');
+// Reference a topic.
+var topic = pubsub.topic('my-topic');
 
 // Publish a message to the topic.
+// The topic will be created if it doesn't exist.
 topic.publish({
   data: 'New message!'
 }, function(err) {});

lib/pubsub/index.js

@@ -160,8 +160,16 @@ PubSub.prototype.getTopics = function(query, callback) {
  *
  * @example
  * pubsub.createTopic('my-new-topic', function(err, topic, apiResponse) {
- *   topic.publish('New message!', function(err) {});
+ *   topic.publish({
+ *     data: 'New message!'
+ *   }, function(err) {});
  * });
+ *
+ * //-
+ * // <strong>Note:</strong> For cases like the one above, it is simpler to use
+ * // {module:pubsub#topic}, which will create the topic for you at the time you
+ * // publish a message.
+ * //-
  */
 PubSub.prototype.createTopic = function(name, callback) {
   callback = callback || util.noop;
@@ -315,14 +323,40 @@ PubSub.prototype.subscription = function(name, options) {
  *
  * @param {string} name - The name of the topic.
  * @param {object=} options - Configuration object.
- * @param {boolean=} options.autoCreate - Automatically create topic if it
+ * @param {boolean} options.autoCreate - Automatically create topic if it
  *     doesn't exist. Note that messages published to a topic with no
- *     subscribers will not be delivered.
+ *     subscribers will not be delivered. Default: true.
  * @return {module:pubsub/topic}
  *
  * @example
- * var topic = pubsub.topic('my-existing-topic');
- * var topic = pubsub.topic('topic-that-maybe-exists', { autoCreate: true });
+ * //-
+ * // By default, it isn't required to specify a topic that already exists. The
+ * // first time you publish a message, the topic will be created for you.
+ * //
+ * // This will only cost one additional API request at the time of publishing.
+ * // If the topic doesn't need to be created, there is no performance penalty.
+ * //-
+ * var topic = pubsub.topic('my-topic');
+ *
+ * topic.publish({
+ *   data: 'New message!'
+ * }, function(err) {});
+ *
+ * //-
+ * // If you prefer an error when trying to publish to a topic that doesn't
+ * // exist, set `autoCreate` to `false`.
+ * //-
+ * var nonExistentTopic = pubsub.topic('my-non-existent-topic', {
+ *   autoCreate: false
+ * });
+ *
+ * nonExistentTopic.publish({
+ *   data: 'New message!'
+ * }, function(err) {
+ *   if (err) {
+ *     // API error from trying to publish a message to a non-existent topic.
+ *   }
+ * });
  */
 PubSub.prototype.topic = function(name, options) {
   if (!name) {

lib/pubsub/subscription.js

@@ -76,23 +76,23 @@ var util = require('../common/util.js');
  * //-
  * // From {@linkcode module:pubsub/topic#getSubscriptions}:
  * //-
- * var topic = pubsub.topic('my-existing-topic');
+ * var topic = pubsub.topic('my-topic');
  * topic.getSubscriptions(function(err, subscriptions) {
  *   // `subscriptions` is an array of Subscription objects.
  * });
  *
  * //-
  * // From {@linkcode module:pubsub/topic#subscribe}:
  * //-
- * var topic = pubsub.topic('my-existing-topic');
+ * var topic = pubsub.topic('my-topic');
  * topic.subscribe('new-subscription', function(err, subscription) {
  *   // `subscription` is a Subscription object.
  * });
  *
  * //-
  * // From {@linkcode module:pubsub/topic#subscription}:
  * //-
- * var topic = pubsub.topic('my-existing-topic');
+ * var topic = pubsub.topic('my-topic');
  * var subscription = topic.subscription('my-existing-subscription');
  * // `subscription` is a Subscription object.
  *

lib/pubsub/topic.js

@@ -30,12 +30,13 @@ var util = require('../common/util.js');
  *
  * @param {module:pubsub} pubsub - PubSub object.
  * @param {object} options - Configuration object.
+ * @param {boolean=} options.autoCreate - Automatically create topic if it
+ *     doesn't exist. Note that messages published to a topic with no
+ *     subscribers will not be delivered. Default: true.
  * @param {string} options.name - Name of the topic.
  */
 /**
- * A Topic object allows you to interact with a Google Cloud Pub/Sub topic. To
- * get this object, you will use the methods on the `pubsub` object,
- * {@linkcode module:pubsub#topic} and {@linkcode module:pubsub#createTopic}.
+ * A Topic object allows you to interact with a Google Cloud Pub/Sub topic.
  *
  * @constructor
  * @alias module:pubsub/topic
@@ -45,25 +46,15 @@ var util = require('../common/util.js');
  *   projectId: 'grape-spaceship-123'
  * });
  *
- * // From pubsub.topic:
- * var topic = pubsub.topic('my-existing-topic');
- *
- * // From pubsub.createTopic:
- * pubsub.createTopic('my-new-topic', function(err, topic) {
- *   // `topic` is a Topic object.
- * });
+ * var topic = pubsub.topic('my-topic');
  */
 function Topic(pubsub, options) {
-  this.makeReq_ = pubsub.makeReq_.bind(pubsub);
+  this.autoCreate = options.autoCreate !== false;
   this.name = Topic.formatName_(pubsub.projectId, options.name);
+
   this.projectId = pubsub.projectId;
   this.pubsub = pubsub;
   this.unformattedName = options.name;
-
-  if (options.autoCreate) {
-    this.origMakeReq_ = this.makeReq_;
-    this.makeReq_ = this.autoCreateWrapper_;
-  }
 }
 
 /**
@@ -99,34 +90,6 @@ Topic.formatName_ = function(projectId, name) {
   return 'projects/' + projectId + '/topics/' + name;
 };
 
-/**
- * Wrapper for makeReq_ that automatically attempts to create a topic if it does
- * not yet exist.
- *
- * @private
- */
-Topic.prototype.autoCreateWrapper_ = function(method, path, q, body, callback) {
-  var self = this;
-
-  function createAndRetry() {
-    self.pubsub.createTopic(self.unformattedName, function(err) {
-      if (err) {
-        callback(err);
-        return;
-      }
-      self.origMakeReq_(method, path, q, body, callback);
-    });
-  }
-
-  this.origMakeReq_(method, path, q, body, function(err, res) {
-    if (err && err.code === 404 && method !== 'DELETE') {
-      createAndRetry();
-    } else {
-      callback(err, res);
-    }
-  });
-};
-
 /**
  * Publish the provided message or array of messages. On success, an array of
  * messageIds is returned in the response.
@@ -144,7 +107,7 @@ Topic.prototype.autoCreateWrapper_ = function(method, path, q, body, callback) {
  * topic.publish({
  *   data: 'Hello, world!'
  * }, function(err, messageIds, apiResponse) {});
- * 
+ *
  * //-
  * // The data property can be a JSON object as well.
  * //-
@@ -159,7 +122,7 @@ Topic.prototype.autoCreateWrapper_ = function(method, path, q, body, callback) {
  *     hello: 'world'
  *   }
  * };
- * 
+ *
  * topic.publish(registerMessage, function(err, messageIds, apiResponse) {});
  *
  * //-
@@ -321,4 +284,40 @@ Topic.prototype.subscription = function(name, options) {
   return this.pubsub.subscription(name, options);
 };
 
+/**
+ * Make an API request using the parent PubSub object's `makeReq_`. If the Topic
+ * instance has `autoCreate: true` set, this method will first try to create the
+ * Topic in the event of a 404.
+ *
+ * @private
+ *
+ * @param {string} method - Action.
+ * @param {string} path - Request path.
+ * @param {*} query - Request query object.
+ * @param {*} body - Request body contents.
+ * @param {function} callback - The callback function.
+ */
+Topic.prototype.makeReq_ = function(method, path, query, body, callback) {
+  var self = this;
+
+  function createTopicThenRetryRequest() {
+    self.pubsub.createTopic(self.unformattedName, function(err, topic, res) {
+      if (err) {
+        callback(err, null, res);
+        return;
+      }
+
+      self.pubsub.makeReq_(method, path, query, body, callback);
+    });
+  }
+
+  this.pubsub.makeReq_(method, path, query, body, function(err, res) {
+    if (self.autoCreate && err && err.code === 404 && method !== 'DELETE') {
+      createTopicThenRetryRequest();
+    } else {
+      callback(err, res);
+    }
+  });
+};
+
 module.exports = Topic;

system-test/pubsub.js

@@ -63,7 +63,6 @@ describe('pubsub', function() {
   });
 
   describe('Topic', function() {
-
     it('should be listed', function(done) {
       pubsub.getTopics(function(err, topics) {
         assert.ifError(err);
@@ -98,6 +97,25 @@ describe('pubsub', function() {
       });
     });
 
+    it('should lazily create by default', function(done) {
+      var newTopicName = generateTopicName();
+      var newTopic = pubsub.topic(newTopicName);
+
+      newTopic.publish({ data: 'message from me' }, function(err) {
+        assert.ifError(err);
+
+        pubsub.getTopics(function(err, topics) {
+          assert.ifError(err);
+
+          assert(topics.some(function(topic) {
+            return topic.name.indexOf(newTopicName) > -1;
+          }));
+
+          newTopic.delete(done);
+        });
+      });
+    });
+
     it('should publish a message', function(done) {
       var topic = pubsub.topic(TOPIC_NAMES[0]);
       topic.publish({ data: 'message from me' }, function(err, messageIds) {