Verify not goroutine leaks in the log proxy

**What**
- Add test to verify that the log proxy shutsdown correctly when the
client cancels
- Add test to verify that the log proxy shutsdown correctly when the
logs provider closes the connection

Signed-off-by: Lucas Roesler <roesler.lucas@gmail.com>

gateway/handlers/logs_test.go

@@ -0,0 +1,133 @@
+package handlers
+
+import (
+	"context"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"testing"
+
+	"go.uber.org/goleak"
+)
+
+func Test_logsProxyDoesNotLeakGoroutinesWhenProviderClosesConnection(t *testing.T) {
+	defer goleak.VerifyNoLeaks(t)
+
+	expectedMsg := "name: funcFoo msg: test message"
+
+	// mock log provider that sends one line and immediately closes the connection
+	mockLogsUpstreamEndpoint := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodGet {
+			t.Fatalf("expected method '%s' but got '%s'", http.MethodGet, r.Method)
+		}
+
+		if r.URL.Path != upstreamLogsEndpoint {
+			t.Fatalf("expected path '%s' but got '%s'", upstreamLogsEndpoint, r.URL.Path)
+		}
+
+		w.Header().Set(http.CanonicalHeaderKey("Connection"), "Keep-Alive")
+		w.Header().Set(http.CanonicalHeaderKey("Transfer-Encoding"), "chunked")
+		w.Header().Set(http.CanonicalHeaderKey("Content-Type"), "application/x-ndjson")
+		w.WriteHeader(http.StatusOK)
+
+		msg := fmt.Sprintf("name: %s msg: test message", r.URL.Query().Get("name"))
+		_, err := w.Write([]byte(msg))
+		if err != nil {
+			t.Fatalf("failed to write test log message: %s", err)
+		}
+	}))
+	defer mockLogsUpstreamEndpoint.Close()
+
+	logProviderURL, _ := url.Parse(mockLogsUpstreamEndpoint.URL)
+
+	logHandler := NewLogHandlerFunc(*logProviderURL)
+	testSrv := httptest.NewServer(http.HandlerFunc(logHandler))
+	defer testSrv.Close()
+
+	resp, err := http.Get(testSrv.URL + "?name=funcFoo")
+	if err != nil {
+		t.Fatalf("unexpected error sneding log request: %s", err)
+	}
+
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		t.Fatalf("unexpected error reading teh response body: %s", err)
+	}
+
+	if string(body) != string(expectedMsg) {
+		t.Fatalf("expected log message %s, got: %s", expectedMsg, body)
+	}
+}
+
+func Test_logsProxyDoesNotLeakGoroutinesWhenClientClosesConnection(t *testing.T) {
+	defer goleak.VerifyNoLeaks(t)
+
+	// mock log provider that sends one line and holds until we cancel the context
+	mockLogsUpstreamEndpoint := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		cn, ok := w.(http.CloseNotifier)
+		if !ok {
+			http.Error(w, "cannot stream", http.StatusInternalServerError)
+			return
+		}
+
+		flusher, ok := w.(http.Flusher)
+		if !ok {
+			http.Error(w, "cannot stream", http.StatusInternalServerError)
+			return
+		}
+
+		if r.Method != http.MethodGet {
+			t.Fatalf("expected method '%s' but got '%s'", http.MethodGet, r.Method)
+		}
+
+		if r.URL.Path != upstreamLogsEndpoint {
+			t.Fatalf("expected path '%s' but got '%s'", upstreamLogsEndpoint, r.URL.Path)
+		}
+
+		w.Header().Set(http.CanonicalHeaderKey("Connection"), "Keep-Alive")
+		w.Header().Set(http.CanonicalHeaderKey("Transfer-Encoding"), "chunked")
+		w.Header().Set(http.CanonicalHeaderKey("Content-Type"), "application/x-ndjson")
+		w.WriteHeader(http.StatusOK)
+
+		msg := fmt.Sprintf("name: %s msg: test message", r.URL.Query().Get("name"))
+		_, err := w.Write([]byte(msg))
+		if err != nil {
+			t.Fatalf("failed to write test log message: %s", err)
+		}
+
+		flusher.Flush()
+
+		// "wait for connection to close"
+		<-cn.CloseNotify()
+
+	}))
+	defer mockLogsUpstreamEndpoint.Close()
+
+	logProviderURL, _ := url.Parse(mockLogsUpstreamEndpoint.URL)
+
+	logHandler := NewLogHandlerFunc(*logProviderURL)
+	testSrv := httptest.NewServer(http.HandlerFunc(logHandler))
+	defer testSrv.Close()
+
+	reqContext, cancel := context.WithCancel(context.Background())
+	req, _ := http.NewRequest(http.MethodGet, testSrv.URL+"?name=funcFoo", nil)
+
+	req = req.WithContext(reqContext)
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatalf("unexpected error sending log request: %s", err)
+	}
+
+	go func() {
+		defer resp.Body.Close()
+		_, err := ioutil.ReadAll(resp.Body)
+		if err != context.Canceled {
+			t.Fatalf("unexpected error reading the response body: %s", err)
+		}
+	}()
+
+	cancel()
+}