Use request.URL.Host instead when request.Host is empty

plugins/http/client_intercepter.go

@@ -30,12 +30,18 @@ type ClientInterceptor struct {
 
 func (h *ClientInterceptor) BeforeInvoke(invocation operator.Invocation) error {
 	request := invocation.Args()[0].(*http.Request)
-	s, err := tracing.CreateExitSpan(fmt.Sprintf("%s:%s", request.Method, request.URL.Path), request.Host, func(headerKey, headerValue string) error {
+	host := request.Host
+	if host == "" {
+		if request.URL != nil {
+			host = request.URL.Host
+		}
+	}
+	s, err := tracing.CreateExitSpan(fmt.Sprintf("%s:%s", request.Method, request.URL.Path), host, func(headerKey, headerValue string) error {
 		request.Header.Add(headerKey, headerValue)
 		return nil
 	}, tracing.WithLayer(tracing.SpanLayerHTTP),
 		tracing.WithTag(tracing.TagHTTPMethod, request.Method),
-		tracing.WithTag(tracing.TagURL, request.Host+request.URL.Path),
+		tracing.WithTag(tracing.TagURL, host+request.URL.Path),
 		tracing.WithComponent(5005))
 	if err != nil {
 		return err

plugins/http/client_intercepter_test.go

@@ -50,6 +50,18 @@ func TestClientInvoke(t *testing.T) {
 	assert.Nil(t, err, "after invoke error should be nil")
 
 	time.Sleep(100 * time.Millisecond)
+
+	reqWithoutHost, err := http.NewRequest("GET", "/api/hello", http.NoBody) // Create request with path only, will result empty Request.Host
+	// Set URL after is valid behavior
+	reqWithoutHost.URL.Scheme = "http"
+	reqWithoutHost.URL.Host = "localhost"
+	assert.Nil(t, err, "new request with no host in url should be no error")
+	invocationWithoutHost := operator.NewInvocation(nil, reqWithoutHost)
+	err = interceptor.BeforeInvoke(invocationWithoutHost)
+	assert.Nil(t, err, "BeforeInvoke with URL.Host should be no error")
+
+	time.Sleep(100 * time.Millisecond)
+
 	spans := core.GetReportedSpans()
 	assert.NotNil(t, spans, "spans should not be nil")
 	assert.Equal(t, 1, len(spans), "spans length should be 1")