bigquery: implement Job as an event emitter (#1294)

stephenplusplus · callmehiphop · commit e4d991a8d84c · 2016-05-11T23:43:40.000-04:00
* bigquery: implement Job as an event emitter

* add tests
diff --git a/lib/bigquery/index.js b/lib/bigquery/index.js
@@ -468,7 +468,7 @@ BigQuery.prototype.job = function(id) {
  *   });
  */
 BigQuery.prototype.query = function(options, callback) {
-  var that = this;
+  var self = this;
 
   if (is.string(options)) {
     options = {
@@ -485,13 +485,13 @@ BigQuery.prototype.query = function(options, callback) {
 
   if (job) {
     // Get results of the query.
-    that.request({
+    self.request({
       uri: '/queries/' + job.id,
       qs: requestQuery
     }, responseHandler);
   } else {
     // Create a job.
-    that.request({
+    self.request({
       method: 'POST',
       uri: '/queries',
       json: options
@@ -521,7 +521,7 @@ BigQuery.prototype.query = function(options, callback) {
     }
     if (nextQuery && !nextQuery.job && resp.jobReference.jobId) {
       // Create a prepared Job to continue the query.
-      nextQuery.job = that.job(resp.jobReference.jobId);
+      nextQuery.job = self.job(resp.jobReference.jobId);
     }
 
     callback(null, rows, nextQuery, resp);
diff --git a/lib/bigquery/job.js b/lib/bigquery/job.js
@@ -20,8 +20,9 @@
 
 'use strict';
 
+var events = require('events');
 var is = require('is');
-var nodeutil = require('util');
+var modelo = require('modelo');
 
 /**
  * @type {module:common/service-object}
@@ -72,6 +73,30 @@ var util = require('../common/util.js');
  * var bigquery = gcloud.bigquery();
  *
  * var job = bigquery.job('job-id');
+ *
+ * //-
+ * // All jobs are event emitters. The status of each job is polled
+ * // continuously, starting only after you register a "complete" listener.
+ * //-
+ * job.on('complete', function(metadata) {
+ *   // The job is complete.
+ * });
+ *
+ * //-
+ * // Be sure to register an error handler as well to catch any issues which
+ * // impeded the job.
+ * //-
+ * job.on('error', function(err) {
+ *   // An error occurred during the job.
+ * });
+ *
+ * //-
+ * // To force the Job object to stop polling for updates, simply remove any
+ * // "complete" listeners you've registered.
+ * //
+ * // The easiest way to do this is with `removeAllListeners()`.
+ * //-
+ * job.removeAllListeners();
  */
 function Job(bigQuery, id) {
   var methods = {
@@ -126,6 +151,8 @@ function Job(bigQuery, id) {
     methods: methods
   });
 
+  events.EventEmitter.call(this);
+
   this.bigQuery = bigQuery;
 
   // The API endpoint for cancel is:    .../bigquery/v2/project/projectId/...
@@ -139,9 +166,14 @@ function Job(bigQuery, id) {
       return reqOpts;
     }
   });
+
+  this.completeListeners = 0;
+  this.hasActiveListeners = false;
+
+  this.listenForEvents_();
 }
 
-nodeutil.inherits(Job, ServiceObject);
+modelo.inherits(Job, ServiceObject, events.EventEmitter);
 
 /**
  * Cancel a job. Use {module:bigquery/job#getMetadata} to see if the cancel
@@ -156,35 +188,9 @@ nodeutil.inherits(Job, ServiceObject);
  * @example
  * job.cancel(function(err, apiResponse) {
  *   // Check to see if the job completes successfully.
- *   onJobComplete(function(err) {
- *     if (!err) {
- *       // Job cancelled successfully.
- *     }
- *   });
+ *   job.on('error', function(err) {});
+ *   job.on('complete', function(metadata) {});
  * });
- *
- * function onJobComplete(callback) {
- *   // Start a loop to check the status of the operation.
- *   checkJobStatus();
- *
- *   function checkJobStatus() {
- *     job.getMetadata(function(err, apiResponse) {
- *       if (err) {
- *         callback(err);
- *         return;
- *       }
- *
- *       if (apiResponse.status.state !== 'DONE') {
- *         // Job has not completed yet. Check again in 3 seconds.
- *         setTimeout(checkJobStatus, 3000);
- *         return;
- *       }
- *
- *       // Job completed sucessfully.
- *       callback();
- *     });
- *   }
- * }
  */
 Job.prototype.cancel = function(callback) {
   callback = callback || util.noop;
@@ -279,4 +285,70 @@ Job.prototype.getQueryResults = function(options, callback) {
   return this.bigQuery.query(options, callback);
 };
 
+/**
+ * Begin listening for events on the job. This method keeps track of how many
+ * "complete" listeners are registered and removed, making sure polling is
+ * handled automatically.
+ *
+ * As long as there is one active "complete" listener, the connection is open.
+ * When there are no more listeners, the polling stops.
+ *
+ * @private
+ */
+Job.prototype.listenForEvents_ = function() {
+  var self = this;
+
+  this.on('newListener', function(event) {
+    if (event === 'complete') {
+      self.completeListeners++;
+
+      if (!self.hasActiveListeners) {
+        self.hasActiveListeners = true;
+        self.startPolling_();
+      }
+    }
+  });
+
+  this.on('removeListener', function(event) {
+    if (event === 'complete' && --self.completeListeners === 0) {
+      self.hasActiveListeners = false;
+    }
+  });
+};
+
+/**
+ * Poll `getMetadata` to check the operation's status. This runs a loop to ping
+ * the API on an interval.
+ *
+ * Note: This method is automatically called once a "complete" event handler is
+ * registered on the operation.
+ *
+ * @private
+ */
+Job.prototype.startPolling_ = function() {
+  var self = this;
+
+  if (!this.hasActiveListeners) {
+    return;
+  }
+
+  this.getMetadata(function(err, metadata, apiResponse) {
+    if (apiResponse.status && apiResponse.status.errors) {
+      err = util.ApiError(apiResponse.status);
+    }
+
+    if (err) {
+      self.emit('error', err);
+      return;
+    }
+
+    if (metadata.status.state !== 'DONE') {
+      setTimeout(self.startPolling_.bind(self), 500);
+      return;
+    }
+
+    self.emit('complete', metadata);
+  });
+};
+
 module.exports = Job;
diff --git a/lib/bigquery/table.js b/lib/bigquery/table.js
@@ -276,7 +276,10 @@ Table.mergeSchemaWithRows_ = function(schema, rows) {
  *
  * @example
  * var yourTable = dataset.table('your-table');
- * table.copy(yourTable, function(err, job, apiResponse) {});
+ * table.copy(yourTable, function(err, job, apiResponse) {
+ *   // `job` is a Job object that can be used to check the status of the
+ *   // request.
+ * });
  *
  * //-
  * // See the [`configuration.copy`](http://goo.gl/dKWIyS) object for all
@@ -387,11 +390,8 @@ Table.prototype.createReadStream = function() {
  * request.get(csvUrl)
  *   .pipe(table.createWriteStream(metadata))
  *   .on('complete', function(job) {
- *     // job is a Job object, which you can use to check the status of the load
- *     // operation.
- *     job.getMetadata(function(err, metadata) {
- *       // metadata.status
- *     });
+ *     // `job` is a Job object that can be used to check the status of the
+ *     // request.
  *   });
  *
  * //-
@@ -499,7 +499,10 @@ Table.prototype.createWriteStream = function(metadata) {
  * // If you wish to override this, or provide an array of destination files,
  * // you must provide an `options` object.
  * //-
- * table.export(exportedFile, function(err, job, apiResponse) {});
+ * table.export(exportedFile, function(err, job, apiResponse) {
+ *   // `job` is a Job object that can be used to check the status of the
+ *   // request.
+ * });
  *
  * //-
  * // If you need more customization, pass an `options` object.
@@ -737,7 +740,10 @@ Table.prototype.getRows = function(options, callback) {
  * //-
  * // Load data from a local file.
  * //-
- * table.import('./institutions.csv', function(err, job, apiResponse) {});
+ * table.import('./institutions.csv', function(err, job, apiResponse) {
+ *   // `job` is a Job object that can be used to check the status of the
+ *   // request.
+ * });
  *
  * //-
  * // You may also pass in metadata in the format of a Jobs resource. See
diff --git a/system-test/bigquery.js b/system-test/bigquery.js
@@ -203,38 +203,20 @@ describe('BigQuery', function() {
   });
 
   it('should cancel a job', function(done) {
-    var query = 'SELECT * FROM [publicdata:samples.github_nested]';
+    var query = 'SELECT url FROM [publicdata:samples.github_nested] LIMIT 10';
 
     bigquery.startQuery(query, function(err, job) {
       assert.ifError(err);
 
       job.cancel(function(err) {
         assert.ifError(err);
-        onJobComplete(done);
-      });
-
-      function onJobComplete(callback) {
-        // Start a loop to check the status of the operation.
-        checkJobStatus();
-
-        function checkJobStatus() {
-          job.getMetadata(function(err, apiResponse) {
-            if (err) {
-              callback(err);
-              return;
-            }
-
-            if (apiResponse.status.state !== 'DONE') {
-              // Job has not completed yet. Check again in 3 seconds.
-              setTimeout(checkJobStatus, 3000);
-              return;
-            }
 
-            // Job completed sucessfully.
-            callback();
+        job
+          .on('error', done)
+          .on('complete', function() {
+            done();
           });
-        }
-      }
+      });
     });
   });
 
@@ -346,8 +328,12 @@ describe('BigQuery', function() {
       it('should import data from a file in your bucket', function(done) {
         table.import(file, function(err, job) {
           assert.ifError(err);
-          assert(job instanceof Job);
-          done();
+
+          job
+            .on('error', done)
+            .on('complete', function() {
+              done();
+            });
         });
       });
 
@@ -395,7 +381,17 @@ describe('BigQuery', function() {
       });
 
       it('should export data to a file in your bucket', function(done) {
-        table.export(bucket.file('kitten-test-data-backup.json'), done);
+        var file = bucket.file('kitten-test-data-backup.json');
+
+        table.export(file, function(err, job) {
+          assert.ifError(err);
+
+          job
+            .on('error', done)
+            .on('complete', function() {
+              done();
+            });
+        });
       });
     });
   });
diff --git a/test/bigquery/job.js b/test/bigquery/job.js
