Added user-agent setting code, and a test for it

src/node/src/client.js

@@ -47,6 +47,7 @@ var Readable = stream.Readable;
 var Writable = stream.Writable;
 var Duplex = stream.Duplex;
 var util = require('util');
+var version = require('../package.json').version;
 
 util.inherits(ClientWritableStream, Writable);
 
@@ -517,7 +518,10 @@ function makeClientConstructor(methods, serviceName) {
         callback(null, metadata);
       };
     }
-
+    if (!options) {
+      options = {};
+    }
+    options.GRPC_ARG_PRIMARY_USER_AGENT_STRING = 'grpc-node/' + version;
     this.server_address = address.replace(/\/$/, '');
     this.channel = new grpc.Channel(address, options);
     this.auth_uri = this.server_address + '/' + serviceName;

src/node/test/surface_test.js

@@ -258,6 +258,16 @@ describe('Echo metadata', function() {
     });
     call.end();
   });
+  it('shows the correct user-agent string', function(done) {
+    var version = require('../package.json').version;
+    var call = client.unary({}, function(err, data) {
+      assert.ifError(err);
+    }, {key: ['value']});
+    call.on('metadata', function(metadata) {
+      assert(_.startsWith(metadata['user-agent'], 'grpc-node/' + version));
+      done();
+    });
+  });
 });
 describe('Other conditions', function() {
   var client;