Add automatic exponential backoff retry on quota and temporary errors (…

…fix #2)

lib/c2dm.js

@@ -2,6 +2,7 @@ var util = require('util');
 var https = require('https');
 var querystring = require('querystring');
 var emitter = require('events').EventEmitter;
+var retry = require('retry');
 
 function C2DM(config) {
     if (config) {
@@ -76,33 +77,73 @@ C2DM.prototype.send = function(packet, cb) {
     var self = this;
     if (cb) this.once('sent', cb);
 
-    var postData = querystring.stringify(packet);
-    var headers = {
-        //'Connection': 'keep-alive',
-        'Host': 'android.apis.google.com',
-        'Authorization': 'GoogleLogin ' + this.token,
-        'Content-Type': 'application/x-www-form-urlencoded',
-        'Content-length': postData.length
-    };
-    this.c2dmOptions.headers = headers;
-    if (this.keepAlive)
-        headers.Connection = 'keep-alive';
+    var operation = retry.operation();
 
-    var request = https.request(this.c2dmOptions, function(res) {
-        var data = '';
-        function respond() {
-            var idx = data.indexOf('id=');
-            if (idx < 0) {
-                self.emit('sent', data, null);
-            } else {
-                self.emit('sent', null, data.substring(idx));
+    operation.attempt(function(currentAttempt) {
+        var postData = querystring.stringify(packet);
+        var headers = {
+            //'Connection': 'keep-alive',
+            'Host': 'android.apis.google.com',
+            'Authorization': 'GoogleLogin ' + self.token,
+            'Content-Type': 'application/x-www-form-urlencoded',
+            'Content-length': postData.length
+        };
+        self.c2dmOptions.headers = headers;
+        if (self.keepAlive)
+            headers.Connection = 'keep-alive';
+
+        var request = https.request(self.c2dmOptions, function(res) {
+            var data = '';
+
+            if (res.statusCode == 503) {
+                // If the server is temporary unavailable, the C2DM spec requires that we implement exponential backoff
+                // and respect any Retry-After header
+                if (res.headers['retry-after']) {
+                    var retrySeconds = res.headers['retry-after'] * 1; // force number
+                    if (isNaN(retrySeconds)) {
+                        // The Retry-After header is a HTTP-date, try to parse it
+                        retrySeconds = new Date(res.headers['retry-after']).getTime() - new Date().getTime();
+                    }
+                    if (!isNaN(retrySeconds) && retrySeconds > 0) {
+                        operation._timeouts['minTimeout'] = retrySeconds;
+                    }
+                }
+                if (!operation.retry('TemporaryUnavailable')) {
+                    self.emit('sent', operation.mainError(), null);
+                }
+                // Ignore all subsequent events for this request
+                return;
             }
-        }
-        res.on('data', function(chunk) {
+
+            function respond() {
+                var error = null, id = null;
+
+                if (data.indexOf('Error=') === 0) {
+                    error = data.substring(6).trim();
+                }
+                else if (data.indexOf('id=') === 0) {
+                    id = data.substring(3).trim();
+                }
+                else {
+                    // No id nor error?
+                    error = 'InvalidServerResponse';
+                }
+
+                // Only retry if error is QuotaExceeded or DeviceQuotaExceeded
+                if (operation.retry(['QuotaExceeded', 'DeviceQuotaExceeded', 'InvalidServerResponse'].indexOf(error) >= 0 ? error : null)) {
+                    return;
+                }
+
+                // Success, return message id (without id=)
+                self.emit('sent', error, id);
+            }
+
+            res.on('data', function(chunk) {
                 data += chunk;
+            });
+            res.on('end', respond);
+            res.on('close', respond);
         });
-        res.on('end', respond);
-        res.on('close', respond);
+        request.end(postData);
     });
-    request.end(postData);
 };

package.json

@@ -13,5 +13,8 @@
     "url": "http://github.com/SpeCT/node-c2dm.git",
     "web" : "http://github.com/SpeCT/node-c2dm"
   },
-  "engines": { "node": ">= 0.2.0" }
+  "engines": { "node": ">= 0.2.0" },
+  "dependencies": {
+    "retry": ">=0.6.0"
+  }
 }