Merge pull request #21 from goodeggs/flush-callback

Accept a callback for ::flush

src/librato.coffee

@@ -27,17 +27,19 @@ librato.measure = librato.timing # alias
 librato.start = ->
   worker.start()
 
-librato.stop = ->
+librato.stop = (cb) ->
   worker.stop()
-  librato.flush()
-    
-librato.flush = ->
+  librato.flush(cb)
+
+librato.flush = (cb = ->) ->
   gauges = []
   collector.flushTo gauges
   measurement.source = config.source for measurement in gauges
-  if gauges.length
-    client.send {gauges}, (err) ->
-      librato.emit 'error', err if err?
+  return process.nextTick cb unless gauges.length
+
+  client.send {gauges}, (err) ->
+    librato.emit 'error', err if err?
+    cb(err)
 
 librato.middleware = middleware(librato)
 

test/librato.coffee

@@ -52,13 +52,13 @@ describe 'librato', ->
       args = Client::send.getCall(0).args
       names = _(args[0].gauges).pluck('name').value()
       expect(names).to.contain 'this_is_:a_test_2'
-    
+
   describe '::flush', ->
     beforeEach ->
       librato.increment('foo')
       librato.timing('bar')
       librato.flush()
-      
+
     it 'sends data to Librato', ->
       expect(Client::send.calledOnce).to.be true
       args = Client::send.getCall(0).args
@@ -71,3 +71,13 @@ describe 'librato', ->
       librato.flush()
       expect(Client::send.calledOnce).to.be true
 
+    it 'call callback immediately when queue is empty', (done) ->
+      librato.flush (err) ->
+        expect(Client::send.callCount).to.be 1
+        done(err)
+
+    it 'accepts a callback', (done) ->
+      librato.increment('messages')
+      librato.flush (err) ->
+        expect(Client::send.callCount).to.be 2
+        done(err)