listen on default port 8200 if unspecified

CHANGELOG.asciidoc

@@ -13,6 +13,8 @@ https://github.com/elastic/apm-server/compare/9e0a1e281e56044745f1a4f18dcbf00a7f
 
 ==== Added
 
+- Listen on default port 8200 if unspecified {pull}[886]886.
+
 ==== Deprecated
 
 ==== Known Issues

beater/beater.go

@@ -63,6 +63,13 @@ func parseListener(host string) (string, string) {
 // This should only be called once, from Run.
 func (bt *beater) listen() (net.Listener, error) {
 	network, path := parseListener(bt.config.Host)
+	if network == "tcp" {
+		if _, _, err := net.SplitHostPort(path); err != nil {
+			// tack on a port if SplitHostPort fails on what should be a tcp network address
+			// if there were already too many colons, one more won't hurt
+			path = net.JoinHostPort(path, defaultPort)
+		}
+	}
 	lis, err := net.Listen(network, path)
 	if err != nil {
 		return nil, err

beater/config.go

@@ -1,13 +1,16 @@
 package beater
 
 import (
+	"net"
 	"regexp"
 	"time"
 
 	"github.com/elastic/apm-server/sourcemap"
 	"github.com/elastic/beats/libbeat/common"
 )
 
+const defaultPort = "8200"
+
 type Config struct {
 	Host                string          `config:"host"`
 	MaxUnzippedSize     int64           `config:"max_unzipped_size"`
@@ -109,7 +112,7 @@ func replaceVersion(pattern, version string) string {
 
 func defaultConfig(beatVersion string) *Config {
 	return &Config{
-		Host:                "localhost:8200",
+		Host:                net.JoinHostPort("localhost", defaultPort),
 		MaxUnzippedSize:     30 * 1024 * 1024, // 30mb
 		MaxHeaderSize:       1 * 1024 * 1024,  // 1mb
 		ConcurrentRequests:  5,

beater/server_test.go

@@ -54,6 +54,33 @@ func TestServerOk(t *testing.T) {
 	assert.Equal(t, http.StatusAccepted, res.StatusCode, body(t, res))
 }
 
+func TestServerTcpNoPort(t *testing.T) {
+	// possibly flakey but worth it
+	// try to connect to localhost:defaultPort
+	// if connection succeeds, port is in use and skip test
+	// if it fails, make sure it is because connection refused
+	if conn, err := net.DialTimeout("tcp", net.JoinHostPort("localhost", defaultPort), 2*time.Second); err == nil {
+		conn.Close()
+		t.Skipf("default port is in use")
+	} else {
+		if e, ok := err.(*net.OpError); !ok || e.Op != "dial" {
+			// failed for some other reason, not connection refused
+			t.Error(err)
+		}
+	}
+	ucfg, err := common.NewConfigFrom(map[string]interface{}{
+		"host": "localhost",
+	})
+	assert.NoError(t, err)
+	btr, teardown := setupServer(t, ucfg)
+	defer teardown()
+
+	baseUrl, client := btr.client(false)
+	rsp, err := client.Get(baseUrl + HealthCheckURL)
+	assert.NoError(t, err)
+	assert.Equal(t, http.StatusOK, rsp.StatusCode)
+}
+
 func tmpTestUnix(t *testing.T) string {
 	f, err := ioutil.TempFile("", "test-apm-server")
 	assert.NoError(t, err)