cmd/mediaapi-integration-tests: Test downloading same file 100 times

Spawns a GET request for the same file in 100 parallel go routines and
prints the body (which is some error JSON) in case of not 200 OK. Also
prints the number of successful requests.

This of course should take command line arguments for the URL and number
of requests but that can be done as soon as needed.

src/github.com/matrix-org/dendrite/cmd/mediaapi-integration-tests/main.go

@@ -0,0 +1,68 @@
+// Copyright 2017 Vector Creations Ltd
+//
+// 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 main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"sync"
+)
+
+const origin = "matrix.org"
+const mediaID = "rZOBfBHnuOoyqBKUIHAaSbcM"
+
+const requestCount = 100
+
+func main() {
+	httpURL := "http://localhost:7777/api/_matrix/media/v1/download/" + origin + "/" + mediaID
+	jsonResponses := make(chan string)
+
+	var wg sync.WaitGroup
+
+	wg.Add(requestCount)
+
+	for i := 0; i < requestCount; i++ {
+		go func() {
+			defer wg.Done()
+			res, err := http.Get(httpURL)
+			if err != nil {
+				log.Fatal(err)
+			} else {
+				defer res.Body.Close()
+				body, err := ioutil.ReadAll(res.Body)
+				if err != nil {
+					log.Fatal(err)
+				} else {
+					if res.StatusCode != 200 {
+						jsonResponses <- string(body)
+					}
+				}
+			}
+		}()
+	}
+
+	errorCount := 0
+	go func() {
+		for response := range jsonResponses {
+			errorCount++
+			fmt.Println(response)
+		}
+	}()
+
+	wg.Wait()
+	fmt.Printf("%v/%v requests were successful\n", requestCount-errorCount, requestCount)
+}