Update ServerRequest to accept server name (#3619)

* Update ServerRequest to accept server name

* Update docs to include Apache and nginx examples

* Test the server not containing a port

semconv/internal/v2/http.go

@@ -136,14 +136,39 @@ func (c *HTTPConv) ClientRequest(req *http.Request) []attribute.KeyValue {
 }
 
 // ServerRequest returns attributes for an HTTP request received by a server.
+//
+// The server must be the primary server name if it is known. For example this
+// would be the ServerName directive
+// (https://httpd.apache.org/docs/2.4/mod/core.html#servername) for an Apache
+// server, and the server_name directive
+// (http://nginx.org/en/docs/http/ngx_http_core_module.html#server_name) for an
+// nginx server. More generically, the primary server name would be the host
+// header value that matches the default virtual host of an HTTP server. It
+// should include the host identifier and if a port is used to route to the
+// server that port identifier should be included as an appropriate port
+// suffix.
+//
+// If the primary server name is not known, server should be an empty string.
+// The req Host will be used to determine the server instead.
+//
 // The following attributes are always returned: "http.method", "http.scheme",
 // "http.flavor", "http.target", "net.host.name". The following attributes are
 // returned if they related values are defined in req: "net.host.port",
 // "net.sock.peer.addr", "net.sock.peer.port", "http.user_agent", "enduser.id",
 // "http.client_ip".
-func (c *HTTPConv) ServerRequest(req *http.Request) []attribute.KeyValue {
+func (c *HTTPConv) ServerRequest(server string, req *http.Request) []attribute.KeyValue {
 	n := 5 // Method, scheme, target, proto, and host name.
-	host, p := splitHostPort(req.Host)
+	var host string
+	var p int
+	if server == "" {
+		host, p = splitHostPort(req.Host)
+	} else {
+		// Prioritize the primary server name.
+		host, p = splitHostPort(server)
+		if p < 0 {
+			_, p = splitHostPort(req.Host)
+		}
+	}
 	hostPort := requiredHTTPPort(req.TLS != nil, p)
 	if hostPort > 0 {
 		n++

semconv/internal/v2/http_test.go

@@ -178,13 +178,34 @@ func TestHTTPServerRequest(t *testing.T) {
 			attribute.String("enduser.id", user),
 			attribute.String("http.client_ip", clientIP),
 		},
-		hc.ServerRequest(req))
+		hc.ServerRequest("", req))
+}
+
+func TestHTTPServerName(t *testing.T) {
+	req := new(http.Request)
+	var got []attribute.KeyValue
+	const (
+		host = "test.semconv.server"
+		port = 8080
+	)
+	portStr := strconv.Itoa(port)
+	server := host + ":" + portStr
+	assert.NotPanics(t, func() { got = hc.ServerRequest(server, req) })
+	assert.Contains(t, got, attribute.String("net.host.name", host))
+	assert.Contains(t, got, attribute.Int("net.host.port", port))
+
+	req = &http.Request{Host: "alt.host.name:" + portStr}
+	// The server parameter does not include a port, ServerRequest should use
+	// the port in the request Host field.
+	assert.NotPanics(t, func() { got = hc.ServerRequest(host, req) })
+	assert.Contains(t, got, attribute.String("net.host.name", host))
+	assert.Contains(t, got, attribute.Int("net.host.port", port))
 }
 
 func TestHTTPServerRequestFailsGracefully(t *testing.T) {
 	req := new(http.Request)
 	var got []attribute.KeyValue
-	assert.NotPanics(t, func() { got = hc.ServerRequest(req) })
+	assert.NotPanics(t, func() { got = hc.ServerRequest("", req) })
 	want := []attribute.KeyValue{
 		attribute.String("http.method", "GET"),
 		attribute.String("http.target", ""),