Add a rate limiter, use it to rate limit docker pulls.

pkg/util/throttle_test.go

@@ -0,0 +1,62 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package util
+
+import (
+	"testing"
+	"time"
+)
+
+func TestBasicThrottle(t *testing.T) {
+	ticker := make(chan time.Time, 1)
+	r := newTokenBucketRateLimiterFromTicker(ticker, 3)
+	for i := 0; i < 3; i++ {
+		if !r.CanAccept() {
+			t.Error("unexpected false accept")
+		}
+	}
+	if r.CanAccept() {
+		t.Error("unexpected true accept")
+	}
+}
+
+func TestIncrementThrottle(t *testing.T) {
+	ticker := make(chan time.Time, 1)
+	r := newTokenBucketRateLimiterFromTicker(ticker, 1)
+	if !r.CanAccept() {
+		t.Error("unexpected false accept")
+	}
+	if r.CanAccept() {
+		t.Error("unexpected true accept")
+	}
+	ticker <- time.Now()
+	r.step()
+
+	if !r.CanAccept() {
+		t.Error("unexpected false accept")
+	}
+}
+
+func TestOverBurst(t *testing.T) {
+	ticker := make(chan time.Time, 1)
+	r := newTokenBucketRateLimiterFromTicker(ticker, 3)
+
+	for i := 0; i < 4; i++ {
+		ticker <- time.Now()
+		r.step()
+	}
+}