Adding support for DD_DOGSTATSD_HOST env var

DD_DOGSTATSD_HOST takes precedence over DD_AGENT_HOST but works in the exact same way. This is useful when running multiple DogStatsD clients on the same host where each of them use a different UDS socket. For example the Trace agent might have its own UDS socket, "/var/run/datadog/apm.socket", while the Agent is listening on "/var/run/datadog/dsd.socket" for DogStatsD traffic. Setting "DD_AGENT_HOST" env var would set the same socket for both app. The dedicated "DD_DOGSTATSD_HOST" now allow users to set a socket/host for DogStatsD only.
DataDog · Oct 5, 2021 · 8634aae · 8634aae
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commit 8634aae
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Showing 4 changed files with 122 additions and 17 deletions.
diff --git a/README.md b/README.md
@@ -57,9 +57,16 @@ 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.
-  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.
+* 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 named pipes
+* `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 enable origin detection and set the `DD_ENTITY_ID` environment variable, add the following lines to your application manifest:
 

diff --git a/statsd/statsd.go b/statsd/statsd.go
@@ -64,9 +64,10 @@ traffic instead of UDP.
 const WindowsPipeAddressPrefix = `\\.\pipe\`
 
 const (
-	agentHostEnvVarName = "DD_AGENT_HOST"
-	agentPortEnvVarName = "DD_DOGSTATSD_PORT"
-	defaultUDPPort      = "8125"
+	agentHostEnvVarName     = "DD_AGENT_HOST"
+	dogstatsdHostEnvVarName = "DD_DOGSTATSD_HOST"
+	dogstatsdPortEnvVarName = "DD_DOGSTATSD_PORT"
+	defaultUDPPort          = "8125"
 )
 
 /*
@@ -230,8 +231,12 @@ var _ ClientInterface = &Client{}
 func resolveAddr(addr string) string {
 	envPort := ""
 	if addr == "" {
-		addr = os.Getenv(agentHostEnvVarName)
-		envPort = os.Getenv(agentPortEnvVarName)
+		if dsdHost := os.Getenv(dogstatsdHostEnvVarName); dsdHost != "" {
+			addr = dsdHost
+		} else {
+			addr = os.Getenv(agentHostEnvVarName)
+		}
+		envPort = os.Getenv(dogstatsdPortEnvVarName)
 	}
 
 	if addr == "" {

diff --git a/statsd/statsd_test.go b/statsd/statsd_test.go
@@ -192,11 +192,11 @@ func TestResolveAddressFromEnvironment(t *testing.T) {
 	} else {
 		defer os.Unsetenv(agentHostEnvVarName)
 	}
-	portInitialValue, portInitiallySet := os.LookupEnv(agentPortEnvVarName)
+	portInitialValue, portInitiallySet := os.LookupEnv(dogstatsdPortEnvVarName)
 	if portInitiallySet {
-		defer os.Setenv(agentPortEnvVarName, portInitialValue)
+		defer os.Setenv(dogstatsdPortEnvVarName, portInitialValue)
 	} else {
-		defer os.Unsetenv(agentPortEnvVarName)
+		defer os.Unsetenv(dogstatsdPortEnvVarName)
 	}
 
 	for _, tc := range []struct {
@@ -224,7 +224,7 @@ func TestResolveAddressFromEnvironment(t *testing.T) {
 	} {
 		t.Run(tc.name, func(t *testing.T) {
 			os.Setenv(agentHostEnvVarName, tc.hostEnv)
-			os.Setenv(agentPortEnvVarName, tc.portEnv)
+			os.Setenv(dogstatsdPortEnvVarName, tc.portEnv)
 
 			addr := resolveAddr(tc.addrParam)
 			assert.Equal(t, tc.expectedAddr, addr)
@@ -269,3 +269,95 @@ func TestGetTelemetry(t *testing.T) {
 	assert.Equal(t, uint64(1), tlm.AggregationNbContextDistribution, "telmetry AggregationNbContextDistribution was wrong")
 	assert.Equal(t, uint64(2), tlm.AggregationNbContextTiming, "telmetry AggregationNbContextTiming was wrong")
 }
+
+func TestEnvAgentHost(t *testing.T) {
+	defer func() { os.Unsetenv("DD_AGENT_HOST") }()
+
+	os.Setenv("DD_AGENT_HOST", "localhost:8765")
+
+	ts, client := newClientAndTestServerCustomAddr(t,
+		"udp",
+		"",
+		"localhost:8765",
+		nil,
+	)
+
+	ts.sendAllAndAssert(t, client)
+}
+
+func TestEnvAgentHostAndPort(t *testing.T) {
+	defer func() { os.Unsetenv("DD_AGENT_HOST") }()
+	defer func() { os.Unsetenv("DD_DOGSTATSD_PORT") }()
+
+	// Check that DD_AGENT_PORT is ignored when DD_AGENT_HOST already contains a port
+	os.Setenv("DD_AGENT_HOST", "localhost:8765")
+	os.Setenv("DD_DOGSTATSD_PORT", "1234")
+
+	ts, client := newClientAndTestServerCustomAddr(t,
+		"udp",
+		"",
+		"localhost:8765",
+		nil,
+	)
+
+	ts.sendAllAndAssert(t, client)
+
+	// Check that DD_DOGSTATSD_PORT is used
+	os.Setenv("DD_AGENT_HOST", "localhost")
+	os.Setenv("DD_DOGSTATSD_PORT", "8766")
+
+	ts, client = newClientAndTestServerCustomAddr(t,
+		"udp",
+		"",
+		"localhost:8766",
+		nil,
+	)
+
+	ts.sendAllAndAssert(t, client)
+}
+
+func TestEnvDogstatsddHost(t *testing.T) {
+	defer func() { os.Unsetenv("DD_DOGSTATSD_HOST") }()
+
+	os.Setenv("DD_DOGSTATSD_HOST", "localhost:8765")
+
+	ts, client := newClientAndTestServerCustomAddr(t,
+		"udp",
+		"",
+		"localhost:8765",
+		nil,
+	)
+
+	ts.sendAllAndAssert(t, client)
+}
+
+func TestEnvDogstatsddHostAndPort(t *testing.T) {
+	defer func() { os.Unsetenv("DD_DOGSTATSD_HOST") }()
+	defer func() { os.Unsetenv("DD_DOGSTATSD_PORT") }()
+
+	// Check that DD_DOGSTATSD_PORT is ignored when DD_AGENT_HOST already contains a port
+	os.Setenv("DD_DOGSTATSD_HOST", "localhost:8765")
+	os.Setenv("DD_DOGSTATSD_PORT", "1234")
+
+	ts, client := newClientAndTestServerCustomAddr(t,
+		"udp",
+		"",
+		"localhost:8765",
+		nil,
+	)
+
+	ts.sendAllAndAssert(t, client)
+
+	// Check that DD_DOGSTATSD_PORT is used
+	os.Setenv("DD_DOGSTATSD_HOST", "localhost")
+	os.Setenv("DD_DOGSTATSD_PORT", "8766")
+
+	ts, client = newClientAndTestServerCustomAddr(t,
+		"udp",
+		"",
+		"localhost:8766",
+		nil,
+	)
+
+	ts.sendAllAndAssert(t, client)
+}
diff --git a/statsd/test_helpers_test.go b/statsd/test_helpers_test.go
@@ -54,7 +54,6 @@ type testServer struct {
 	errors    []string
 	readData  []string
 	proto     string
-	addr      string
 	stopped   chan struct{}
 	tags      string
 	namespace string
@@ -66,14 +65,16 @@ 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{}),
 		aggregation:         opt.aggregation,
 		extendedAggregation: opt.extendedAggregation,
@@ -88,14 +89,14 @@ 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":
-		socketPath := addr[7:]
+		socketPath := addrTest[7:]
 		address, err := net.ResolveUnixAddr("unixgram", socketPath)
 		require.NoError(t, err)
 		conn, err := net.ListenUnixgram("unixgram", address)
@@ -107,7 +108,7 @@ func newClientAndTestServer(t *testing.T, proto string, addr string, tags []stri
 		require.FailNow(t, "unknown proto '%s'", proto)
 	}
 
-	client, err := New(addr, options...)
+	client, err := New(addrClient, options...)
 	require.NoError(t, err)
 
 	go ts.start()