diff --git a/sinks/cortex/cortex.go b/sinks/cortex/cortex.go
index 7a97ca2f2..ffddae882 100644
--- a/sinks/cortex/cortex.go
+++ b/sinks/cortex/cortex.go
@@ -59,6 +59,7 @@ type CortexMetricSink struct {
 }
 
 var _ sinks.MetricSink = (*CortexMetricSink)(nil)
+var DoIfNotDoneError = errors.New("context finished before completing metrics flush")
 
 type BasicAuthType struct {
 	Username util.StringSecret `yaml:"username"`
@@ -222,7 +223,7 @@ func (s *CortexMetricSink) Flush(ctx context.Context, metrics []samplers.InterMe
 	doIfNotDone := func(fn func() error) error {
 		select {
 		case <-ctx.Done():
-			return errors.New("context finished before completing metrics flush")
+			return DoIfNotDoneError
 		default:
 			return fn()
 		}
@@ -235,19 +236,24 @@ func (s *CortexMetricSink) Flush(ctx context.Context, metrics []samplers.InterMe
 			if len(batch)%s.batchWriteSize == 0 {
 				err := s.writeMetrics(ctx, batch)
 				if err != nil {
-					return err
+					s.logger.Error(err)
+					droppedMetrics += len(batch)
+				} else {
+					flushedMetrics += len(batch)
 				}
 
-				flushedMetrics += len(batch)
 				batch = []samplers.InterMetric{}
+				return err
 			}
 
 			return nil
 		})
 
-		if err != nil {
-			s.logger.Error(err)
-			droppedMetrics += len(metrics) - flushedMetrics
+		// Any other type of error will happen inside of doIfNotDone
+		// so we only need ot handle context cancellations
+		if err == DoIfNotDoneError {
+			// Don't bother with the rest of the loop, we're done.
+			droppedMetrics = len(metrics) - flushedMetrics
 			return sinks.MetricFlushResult{MetricsFlushed: flushedMetrics, MetricsDropped: droppedMetrics}, err
 		}
 	}
diff --git a/sinks/cortex/cortex_test.go b/sinks/cortex/cortex_test.go
index 09e8369cb..1ae484f2a 100644
--- a/sinks/cortex/cortex_test.go
+++ b/sinks/cortex/cortex_test.go
@@ -360,7 +360,7 @@ func TestChunkedWritesRespectContextCancellation(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	requestCount := 0
 
-	server.onRequest(func() {
+	server.onRequest(func(w http.ResponseWriter, r *http.Request) {
 		requestCount++
 		if requestCount == 2 {
 			cancel()
@@ -418,6 +418,45 @@ func TestMetricsGetEmittedWithHostTag(t *testing.T) {
 	}
 }
 
+func TestAllBatchesAreAttemptedEvenIfSomeFail(t *testing.T) {
+	// Listen for prometheus writes
+	server := NewTestServer(t)
+	defer server.Close()
+
+	// Set up a sink
+	sink, err := NewCortexMetricSink(server.URL, 30*time.Second, "", logrus.NewEntry(logrus.New()), "test", map[string]string{}, nil, 3, false, "")
+	assert.NoError(t, err)
+	assert.NoError(t, sink.Start(trace.DefaultClient))
+
+	// chunked_input.json contains 12 timeseries samples in InterMetrics format
+	jsInput, err := ioutil.ReadFile("testdata/chunked_input.json")
+	assert.NoError(t, err)
+	var metrics []samplers.InterMetric
+	assert.NoError(t, json.Unmarshal(jsInput, &metrics))
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	requestCount := 0
+
+	server.onRequest(func(w http.ResponseWriter, r *http.Request) {
+		requestCount++
+		if requestCount == 2 {
+			w.WriteHeader(http.StatusInternalServerError)
+			w.Write([]byte("an error!"))
+		}
+	})
+
+	// Perform the flush to the test server
+	flushResult, err := sink.Flush(ctx, metrics)
+	assert.NoError(t, err)
+	assert.Equal(t, sinks.MetricFlushResult{MetricsFlushed: 9, MetricsDropped: 3, MetricsSkipped: 0}, flushResult)
+
+	// ensure we see all chunks written
+	assert.Equal(t, 4, len(server.History()))
+	assert.Equal(t, 3, len(server.History()[0].data.GetTimeseries()))
+	assert.Equal(t, 3, len(server.History()[1].data.GetTimeseries()))
+}
+
 func TestCustomHeaders(t *testing.T) {
 	// Listen for prometheus writes
 	server := NewTestServer(t)
@@ -667,7 +706,7 @@ type TestServer struct {
 	data      *prompb.WriteRequest
 	server    *httptest.Server
 	history   []*RequestHistory
-	requestFn func()
+	requestFn func(w http.ResponseWriter, r *http.Request)
 }
 
 // Close closes the internal test server
@@ -687,7 +726,7 @@ func (t *TestServer) History() []*RequestHistory {
 	return t.history
 }
 
-func (t *TestServer) onRequest(fn func()) {
+func (t *TestServer) onRequest(fn func(w http.ResponseWriter, r *http.Request)) {
 	t.requestFn = fn
 }
 
@@ -721,7 +760,7 @@ func NewTestServer(t *testing.T) *TestServer {
 		})
 
 		if result.requestFn != nil {
-			result.requestFn()
+			result.requestFn(w, r)
 		}
 	})