Add unit test for rate-limit-handler (#2661) (#2784)

cmd/rate-limit-handler.go

@@ -35,32 +35,33 @@ type rateLimit struct {
 // channel this is in-turn used to rate limit incoming connections in
 // ServeHTTP() http.Handler method.
 func (c *rateLimit) acquire() error {
-	//attempt to enter the waitQueue. If no slot is immediately
-	//available return error.
+	// attempt to enter the waitQueue. If no slot is immediately
+	// available return error.
 	select {
 	case c.waitQueue <- struct{}{}:
-		//entered wait queue
+		// entered wait queue
 		break
 	default:
-		//no slot available for waiting
+		// no slot available for waiting
 		return errTooManyRequests
 	}
 
-	//block attempting to enter the workQueue. If the workQueue is
-	//full, there can be at most cap(waitQueue) == 4*globalMaxConn
-	//goroutines waiting here because of the select above.
+	// block attempting to enter the workQueue. If the workQueue
+	// is full, there can be at most cap(waitQueue) ==
+	// 4*globalMaxConn goroutines waiting here because of the
+	// select above.
 	select {
 	case c.workQueue <- struct{}{}:
-		//entered workQueue - so remove one waiter. This step
-		//does not block as the waitQueue cannot be empty.
+		// entered workQueue - so remove one waiter. This step
+		// does not block as the waitQueue cannot be empty.
 		<-c.waitQueue
 	}
 
 	return nil
 }
 
-// Release one element from workQueue to serve a new client
-// in the waiting list
+// Release one element from workQueue to serve a new client in the
+// waiting list
 func (c *rateLimit) release() {
 	<-c.workQueue
 }
@@ -82,13 +83,15 @@ func (c *rateLimit) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	c.release()
 }
 
-// setRateLimitHandler limits the number of concurrent http requests based on MINIO_MAXCONN.
+// setRateLimitHandler limits the number of concurrent http requests
+// based on MINIO_MAXCONN.
 func setRateLimitHandler(handler http.Handler) http.Handler {
 	if globalMaxConn == 0 {
 		return handler
 	} // else proceed to rate limiting.
 
-	// For max connection limit of > '0' we initialize rate limit handler.
+	// For max connection limit of > '0' we initialize rate limit
+	// handler.
 	return &rateLimit{
 		handler:   handler,
 		workQueue: make(chan struct{}, globalMaxConn),

cmd/rate-limit-handler_test.go

@@ -0,0 +1,83 @@
+/*
+ * Minio Cloud Storage, (C) 2016 Minio, Inc.
+ *
+ * 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 cmd
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+)
+
+// This test sets globalMaxConn to 1 and starts 6 connections in
+// parallel on a server with the rate limit handler configured. This
+// should allow one request to execute at a time, and at most 4 to
+// wait to execute and the 6th request should get a 429 status code
+// error.
+func TestRateLimitHandler(t *testing.T) {
+	// save the global Max connections
+	saveGlobalMaxConn := globalMaxConn
+
+	globalMaxConn = 1
+	testHandler := func(w http.ResponseWriter, r *http.Request) {
+		time.Sleep(100 * time.Millisecond)
+		fmt.Fprintln(w, "Hello client!")
+	}
+	rlh := setRateLimitHandler(http.HandlerFunc(testHandler))
+	ts := httptest.NewServer(rlh)
+	respCh := make(chan int)
+	startTime := time.Now()
+	for i := 0; i < 6; i++ {
+		go func(ch chan<- int) {
+			resp, err := http.Get(ts.URL)
+			if err != nil {
+				t.Errorf(
+					"Got error requesting test server - %v\n",
+					err,
+				)
+			}
+			respCh <- resp.StatusCode
+		}(respCh)
+	}
+
+	tooManyReqErrCount := 0
+	for i := 0; i < 6; i++ {
+		code := <-respCh
+		if code == 429 {
+			tooManyReqErrCount++
+		} else if code != 200 {
+			t.Errorf("Got non-200 resp code - %d\n", code)
+		}
+	}
+	duration := time.Since(startTime)
+	if duration < time.Duration(500*time.Millisecond) {
+		// as globalMaxConn is 1, only 1 request will execute
+		// at a time, and the five allowed requested will take
+		// at least 500 ms.
+		t.Errorf("Expected all requests to take at least 500ms, but it was done in %v\n",
+			duration)
+	}
+	if tooManyReqErrCount != 1 {
+		t.Errorf("Expected to get 1 error, but got %d",
+			tooManyReqErrCount)
+	}
+	ts.Close()
+
+	// restore the global Max connections
+	globalMaxConn = saveGlobalMaxConn
+}