From 18203f57d2bd5d2f48ab443a227927bef6e1b86e Mon Sep 17 00:00:00 2001
From: Liam van der Viven <62619917+liamvdv@users.noreply.github.com>
Date: Mon, 29 Jan 2024 17:08:05 +0100
Subject: [PATCH] Add support for sending DogStatsD metrics over Unix Socket

---
 docs/content/observability/metrics/datadog.md |  2 +
 docs/mkdocs.yml                               |  4 ++
 pkg/metrics/datadog.go                        | 27 ++++++++++---
 pkg/metrics/datadog_test.go                   | 39 +++++++++++++++++++
 4 files changed, 67 insertions(+), 5 deletions(-)

diff --git a/docs/content/observability/metrics/datadog.md b/docs/content/observability/metrics/datadog.md
index 00a5d6c9f..134b726df 100644
--- a/docs/content/observability/metrics/datadog.md
+++ b/docs/content/observability/metrics/datadog.md
@@ -27,6 +27,8 @@ _Required, Default="127.0.0.1:8125"_
 
 Address instructs exporter to send metrics to datadog-agent at this address.
 
+This address can be a Unix Domain Socket (UDS) address with the following form: `unix:///path/to/datadog.socket`.  
+
 ```yaml tab="File (YAML)"
 metrics:
   datadog:
diff --git a/docs/mkdocs.yml b/docs/mkdocs.yml
index 6ba875a3f..0b7ffaa2c 100644
--- a/docs/mkdocs.yml
+++ b/docs/mkdocs.yml
@@ -153,7 +153,11 @@ nav:
       - 'Access Logs': 'observability/access-logs.md'
       - 'Metrics':
           - 'Overview': 'observability/metrics/overview.md'
+          - 'Datadog': 'observability/metrics/datadog.md'
+          - 'InfluxDB2': 'observability/metrics/influxdb2.md'
           - 'OpenTelemetry': 'observability/metrics/opentelemetry.md'
+          - 'Prometheus': 'observability/metrics/prometheus.md'
+          - 'StatsD': 'observability/metrics/statsd.md'
       - 'Tracing':
           - 'Overview': 'observability/tracing/overview.md'
           - 'OpenTelemetry': 'observability/tracing/opentelemetry.md'
diff --git a/pkg/metrics/datadog.go b/pkg/metrics/datadog.go
index b09e3407a..fcb8be6d2 100644
--- a/pkg/metrics/datadog.go
+++ b/pkg/metrics/datadog.go
@@ -2,6 +2,7 @@ package metrics
 
 import (
 	"context"
+	"strings"
 	"time"
 
 	"github.com/go-kit/kit/metrics/dogstatsd"
@@ -16,6 +17,8 @@ var (
 	datadogLoopCancelFunc context.CancelFunc
 )
 
+const unixAddressPrefix = "unix://"
+
 // Metric names consistent with https://github.com/DataDog/integrations-extras/pull/64
 const (
 	ddConfigReloadsName           = "config.reload.total"
@@ -99,10 +102,7 @@ func RegisterDatadog(ctx context.Context, config *types.Datadog) Registry {
 }
 
 func initDatadogClient(ctx context.Context, config *types.Datadog) {
-	address := config.Address
-	if len(address) == 0 {
-		address = "localhost:8125"
-	}
+	network, address := parseDatadogAddress(config.Address)
 
 	ctx, datadogLoopCancelFunc = context.WithCancel(ctx)
 
@@ -110,10 +110,27 @@ func initDatadogClient(ctx context.Context, config *types.Datadog) {
 		ticker := time.NewTicker(time.Duration(config.PushInterval))
 		defer ticker.Stop()
 
-		datadogClient.SendLoop(ctx, ticker.C, "udp", address)
+		datadogClient.SendLoop(ctx, ticker.C, network, address)
 	})
 }
 
+func parseDatadogAddress(address string) (string, string) {
+	network := "udp"
+
+	var addr string
+	switch {
+	case strings.HasPrefix(address, unixAddressPrefix):
+		network = "unix"
+		addr = address[len(unixAddressPrefix):]
+	case address != "":
+		addr = address
+	default:
+		addr = "localhost:8125"
+	}
+
+	return network, addr
+}
+
 // StopDatadog stops the Datadog metrics pusher.
 func StopDatadog() {
 	if datadogLoopCancelFunc != nil {
diff --git a/pkg/metrics/datadog_test.go b/pkg/metrics/datadog_test.go
index 6a53bf065..cd4b99433 100644
--- a/pkg/metrics/datadog_test.go
+++ b/pkg/metrics/datadog_test.go
@@ -7,6 +7,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/stvp/go-udp-testing"
 	ptypes "github.com/traefik/paerser/types"
 	"github.com/traefik/traefik/v3/pkg/types"
@@ -39,6 +40,44 @@ func TestDatadogWithPrefix(t *testing.T) {
 	testDatadogRegistry(t, "testPrefix", datadogRegistry)
 }
 
+func TestDatadog_parseDatadogAddress(t *testing.T) {
+	tests := []struct {
+		desc       string
+		address    string
+		expNetwork string
+		expAddress string
+	}{
+		{
+			desc:       "empty address",
+			expNetwork: "udp",
+			expAddress: "localhost:8125",
+		},
+		{
+			desc:       "udp address",
+			address:    "127.0.0.1:8080",
+			expNetwork: "udp",
+			expAddress: "127.0.0.1:8080",
+		},
+		{
+			desc:       "unix address",
+			address:    "unix:///path/to/datadog.socket",
+			expNetwork: "unix",
+			expAddress: "/path/to/datadog.socket",
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.desc, func(t *testing.T) {
+			t.Parallel()
+
+			gotNetwork, gotAddress := parseDatadogAddress(test.address)
+			assert.Equal(t, test.expNetwork, gotNetwork)
+			assert.Equal(t, test.expAddress, gotAddress)
+		})
+	}
+}
+
 func testDatadogRegistry(t *testing.T, metricsPrefix string, datadogRegistry Registry) {
 	t.Helper()