grpc: listen for metadata event instead of status (#1444)

grpc: listen for metadata event instead of status

lib/common/grpc-service.js

@@ -325,10 +325,16 @@ GrpcService.prototype.requestStream = function(protoOpts, reqOpts) {
 
     request: function() {
       return service[protoOpts.method](reqOpts, grpcOpts)
-        .on('status', function(status) {
-          var grcpStatus = GrpcService.decorateStatus_(status);
-
-          this.emit('response', grcpStatus || status);
+        .on('metadata', function() {
+          // retry-request requires a server response before it starts emitting
+          // data. The closest mechanism grpc provides is a metadata event, but
+          // this does not provide any kind of response status. So we're faking
+          // it here with code `0` which translates to HTTP 200.
+          //
+          // https://github.com/GoogleCloudPlatform/gcloud-node/pull/1444#discussion_r71812636
+          var grcpStatus = GrpcService.decorateStatus_({ code: 0 });
+
+          this.emit('response', grcpStatus);
         });
     }
   };

test/common/grpc-service.js

@@ -1062,8 +1062,7 @@ describe('GrpcService', function() {
         );
       });
 
-      it('should emit the status as a response event', function(done) {
-        var grpcError500 = { code: 2 };
+      it('should emit the metadata event as a response event', function(done) {
         var fakeStream = through.obj();
 
         ProtoService.prototype.method = function() {
@@ -1075,13 +1074,14 @@ describe('GrpcService', function() {
         };
 
         fakeStream
+          .on('error', done)
           .on('response', function(resp) {
-            assert.deepEqual(resp, GrpcService.GRPC_ERROR_CODE_TO_HTTP[2]);
+            assert.deepEqual(resp, GrpcService.GRPC_ERROR_CODE_TO_HTTP[0]);
             done();
           });
 
         grpcService.requestStream(PROTO_OPTS, REQ_OPTS);
-        fakeStream.emit('status', grpcError500);
+        fakeStream.emit('metadata');
       });
 
       it('should emit the response error', function(done) {