Add support for DD_DOGSTATSD_HOST

DD_DOGSTATSD_HOST takes precedence over DD_AGENT_HOST but works in the
exact same way. This is useful when running multiple Datadog clients on
the same host where each of them use a different UDS socket for example
(ex: running the trace client and the dogstatsd client).

README.md

@@ -43,9 +43,16 @@ Find a list of all the available options for your DogStatsD Client in the [Datad
 
 ### Supported environment variables
 
-* If the `addr` parameter is empty, the client uses the `DD_AGENT_HOST` environment variables to build a target address.
+* If the `addr` parameter is empty, the client uses the `DD_DOGSTATSD_HOST` and then `DD_AGENT_HOST` environment
+  variables to build a target address. `DD_DOGSTATSD_HOST` takes precedence over `DD_AGENT_HOST`, but both use the same
+  format.
   Example: `DD_AGENT_HOST=127.0.0.1:8125` for UDP, `DD_AGENT_HOST=unix:///path/to/socket` for UDS and `DD_AGENT_HOST=\\.\pipe\my_windows_pipe` for Windows
-* If the `DD_ENTITY_ID` environment variable is found, its value is injected as a global `dd.internal.entity_id` tag. The Datadog Agent uses this tag to insert container tags into the metrics. To avoid overwriting this global tag, only `append` to the `c.Tags` slice.
+* `DD_DOGSTATSD_PORT` can be use to set the UDP port. If `DD_DOGSTATSD_HOST` or `DD_AGENT_HOST` already contains a port
+  then `DD_DOGSTATSD_PORT` is ignored.
+  Example: `DD_AGENT_HOST=127.0.0.1` with `DD_DOGSTATSD_PORT=8125`.
+* If the `DD_ENTITY_ID` environment variable is found, its value is injected as a global `dd.internal.entity_id` tag.
+  The Datadog Agent uses this tag to insert container tags into the metrics. To avoid overwriting this global tag, only
+  `append` to the `c.Tags` slice.
 
 To enable origin detection and set the `DD_ENTITY_ID` environment variable, add the following lines to your application manifest:
 

statsd/statsd.go

@@ -63,9 +63,10 @@ traffic instead of UDP.
 const WindowsPipeAddressPrefix = `\\.\pipe\`
 
 const (
-	agentHostEnvVarName = "DD_AGENT_HOST"
-	agentPortEnvVarName = "DD_DOGSTATSD_PORT"
-	defaultUDPPort      = "8125"
+	agentHostEnvVarName    = "DD_AGENT_HOST"
+	agentDsdHostEnvVarName = "DD_DOGSTATSD_HOST"
+	agentPortEnvVarName    = "DD_DOGSTATSD_PORT"
+	defaultUDPPort         = "8125"
 )
 
 /*
@@ -240,7 +241,11 @@ var _ ClientInterface = &Client{}
 func resolveAddr(addr string) string {
 	envPort := ""
 	if addr == "" {
-		addr = os.Getenv(agentHostEnvVarName)
+		if dsdHost := os.Getenv(agentDsdHostEnvVarName); dsdHost != "" {
+			addr = dsdHost
+		} else {
+			addr = os.Getenv(agentHostEnvVarName)
+		}
 		envPort = os.Getenv(agentPortEnvVarName)
 	}
 

statsd/statsd_test.go

@@ -419,3 +419,101 @@ func TestEnvTagsEmptyString(t *testing.T) {
 	assert.Len(t, client.Tags, 0)
 	ts.sendAllAndAssert(t, client)
 }
+
+func TestDdAgentHost(t *testing.T) {
+	defer func() { os.Unsetenv(agentHostEnvVarName) }()
+
+	os.Setenv(agentHostEnvVarName, "localhost:8765")
+
+	ts, client := newClientAndTestServerCustomAddr(t,
+		"udp",
+		"",
+		"localhost:8765",
+		nil,
+	)
+
+	assert.Len(t, client.Tags, 0)
+	ts.sendAllAndAssert(t, client)
+}
+
+func TestDdAgentHostAndPort(t *testing.T) {
+	defer func() { os.Unsetenv(agentHostEnvVarName) }()
+	defer func() { os.Unsetenv(agentPortEnvVarName) }()
+
+	// Check that DD_AGENT_PORT is ignored when DD_AGENT_HOST already contains a port
+	os.Setenv(agentHostEnvVarName, "localhost:8765")
+	os.Setenv(agentPortEnvVarName, "1234")
+
+	ts, client := newClientAndTestServerCustomAddr(t,
+		"udp",
+		"",
+		"localhost:8765",
+		nil,
+	)
+
+	assert.Len(t, client.Tags, 0)
+	ts.sendAllAndAssert(t, client)
+
+	// Check that DD_DOGSTATSD_PORT is used
+	os.Setenv(agentHostEnvVarName, "localhost")
+	os.Setenv(agentPortEnvVarName, "8766")
+
+	ts, client = newClientAndTestServerCustomAddr(t,
+		"udp",
+		"",
+		"localhost:8766",
+		nil,
+	)
+
+	assert.Len(t, client.Tags, 0)
+	ts.sendAllAndAssert(t, client)
+}
+
+func TestDdDsdHost(t *testing.T) {
+	defer func() { os.Unsetenv(agentDsdHostEnvVarName) }()
+
+	os.Setenv(agentDsdHostEnvVarName, "localhost:8765")
+
+	ts, client := newClientAndTestServerCustomAddr(t,
+		"udp",
+		"",
+		"localhost:8765",
+		nil,
+	)
+
+	assert.Len(t, client.Tags, 0)
+	ts.sendAllAndAssert(t, client)
+}
+
+func TestDdDsdHostAndPort(t *testing.T) {
+	defer func() { os.Unsetenv(agentDsdHostEnvVarName) }()
+	defer func() { os.Unsetenv(agentPortEnvVarName) }()
+
+	// Check that DD_DOGSTATSD_PORT is ignored when DD_AGENT_HOST already contains a port
+	os.Setenv(agentDsdHostEnvVarName, "localhost:8765")
+	os.Setenv(agentPortEnvVarName, "1234")
+
+	ts, client := newClientAndTestServerCustomAddr(t,
+		"udp",
+		"",
+		"localhost:8765",
+		nil,
+	)
+
+	assert.Len(t, client.Tags, 0)
+	ts.sendAllAndAssert(t, client)
+
+	// Check that DD_DOGSTATSD_PORT is used
+	os.Setenv(agentDsdHostEnvVarName, "localhost")
+	os.Setenv(agentPortEnvVarName, "8766")
+
+	ts, client = newClientAndTestServerCustomAddr(t,
+		"udp",
+		"",
+		"localhost:8766",
+		nil,
+	)
+
+	assert.Len(t, client.Tags, 0)
+	ts.sendAllAndAssert(t, client)
+}

statsd/test_helpers_test.go

@@ -52,7 +52,6 @@ type testServer struct {
 	data      []string
 	errors    []string
 	proto     string
-	addr      string
 	stopped   chan struct{}
 	tags      string
 	namespace string
@@ -65,14 +64,16 @@ type testServer struct {
 }
 
 func newClientAndTestServer(t *testing.T, proto string, addr string, tags []string, options ...Option) (*testServer, *Client) {
+	return newClientAndTestServerCustomAddr(t, proto, addr, addr, tags, options...)
+}
 
+func newClientAndTestServerCustomAddr(t *testing.T, proto string, addrClient string, addrTest string, tags []string, options ...Option) (*testServer, *Client) {
 	opt, err := resolveOptions(options)
 	require.NoError(t, err)
 
 	ts := &testServer{
 		proto:               proto,
 		data:                []string{},
-		addr:                addr,
 		stopped:             make(chan struct{}),
 		devMode:             opt.DevMode,
 		aggregation:         opt.Aggregation,
@@ -88,21 +89,21 @@ func newClientAndTestServer(t *testing.T, proto string, addr string, tags []stri
 
 	switch proto {
 	case "udp":
-		udpAddr, err := net.ResolveUDPAddr("udp", addr)
+		udpAddr, err := net.ResolveUDPAddr("udp", addrTest)
 		require.NoError(t, err)
 
 		conn, err := net.ListenUDP("udp", udpAddr)
 		require.NoError(t, err)
 		ts.conn = conn
 	case "uds":
-		conn, err := net.Dial("unix", addr[:7]) // we remove the 'unix://' prefix
+		conn, err := net.Dial("unix", addrTest[:7]) // we remove the 'unix://' prefix
 		require.NoError(t, err)
 		ts.conn = conn
 	default:
 		require.FailNow(t, "unknown proto '%s'", proto)
 	}
 
-	client, err := New(addr, options...)
+	client, err := New(addrClient, options...)
 	require.NoError(t, err)
 
 	go ts.start()