Updated dockerstatsreceiver to respect DOCKER_HOST env variable.

.chloggen/update-docker.yaml

@@ -0,0 +1,13 @@
+change_type: enhancement  
+
+component: dockerstatsreceiver  
+
+note: "Respect the `DOCKER_HOST` environment variable when resolving the Docker endpoint. The receiver now prioritizes the endpoint in the following order: YAML config > `DOCKER_HOST` env variable > default `unix:///var/run/docker.sock`."  
+
+issues: [35779]  
+
+subtext: |  
+  - Previously, the receiver required explicit configuration of the endpoint.  
+  - This change allows automatic detection of `DOCKER_HOST`, improving flexibility in different environments.  
+
+change_logs: []  

receiver/dockerstatsreceiver/config.go

@@ -36,6 +36,7 @@ type Config struct {
 
 	// MetricsBuilderConfig config. Enable or disable stats by name.
 	metadata.MetricsBuilderConfig `mapstructure:",squash"`
+	Endpoint                      string
 }
 
 func (config Config) Validate() error {

receiver/dockerstatsreceiver/receiver.go

@@ -6,6 +6,7 @@ package dockerstatsreceiver // import "github.com/open-telemetry/opentelemetry-c
 import (
 	"context"
 	"fmt"
+	"os"
 	"strconv"
 	"strings"
 	"sync"
@@ -44,6 +45,22 @@ type metricsReceiver struct {
 	cancel   context.CancelFunc
 }
 
+const (
+	defaultEndpoint = "unix:///var/run/docker.sock"
+	dockerHostEnv   = "DOCKER_HOST"
+)
+
+func (c *Config) resolveDockerEndpoint() string {
+	if c.Endpoint != "" {
+		return c.Endpoint
+	}
+
+	if dockerHost := os.Getenv(dockerHostEnv); dockerHost != "" {
+		return dockerHost
+	}
+	return defaultEndpoint
+}
+
 func newMetricsReceiver(set receiver.Settings, config *Config) *metricsReceiver {
 	return &metricsReceiver{
 		config:   config,
@@ -53,6 +70,9 @@ func newMetricsReceiver(set receiver.Settings, config *Config) *metricsReceiver
 }
 
 func (r *metricsReceiver) start(ctx context.Context, _ component.Host) error {
+	// Resolve the Docker endpoint before creating the client
+	r.config.Endpoint = r.config.resolveDockerEndpoint()
+
 	var err error
 	r.client, err = docker.NewDockerClient(&r.config.Config, r.settings.Logger)
 	if err != nil {

receiver/dockerstatsreceiver/receiver_test.go

@@ -120,6 +120,72 @@ var (
 	}
 )
 
+const (
+	DefaultEndpoint = "unix:///var/run/docker.sock"
+	DockerHostEnv   = "DOCKER_HOST"
+)
+
+func TestResolveDockerEndpoint(t *testing.T) {
+	tests := []struct {
+		name        string
+		cfg         Config
+		env         string
+		expected    string
+		description string
+	}{
+		{
+			name:        "Explicit endpoint in config",
+			cfg:         Config{Endpoint: "tcp://192.168.1.100:2375"},
+			expected:    "tcp://192.168.1.100:2375",
+			description: "Should return the endpoint from the config if it's set.",
+		},
+		{
+			name:        "DOCKER_HOST env variable set",
+			cfg:         Config{},
+			env:         "tcp://dockerhost:2376",
+			expected:    "tcp://dockerhost:2376",
+			description: "Should return the value of the DOCKER_HOST environment variable.",
+		},
+		{
+			name:        "Default endpoint",
+			cfg:         Config{},
+			expected:    defaultEndpoint,
+			description: "Should return the default endpoint if no config or env variable is set.",
+		},
+		{
+			name:        "Empty DOCKER_HOST env variable",
+			cfg:         Config{},
+			env:         "", // Explicitly set to empty string
+			expected:    defaultEndpoint,
+			description: "Should return the default endpoint if DOCKER_HOST is empty.",
+		},
+		{
+			name:        "Config takes precedence over DOCKER_HOST",
+			cfg:         Config{Endpoint: "tcp://config:1234"},
+			env:         "tcp://env:5678",
+			expected:    "tcp://config:1234",
+			description: "Should return the config endpoint even if DOCKER_HOST is set.",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			// Set the environment variable for the test
+			if tt.env != "" {
+				os.Setenv(dockerHostEnv, tt.env)
+				defer os.Unsetenv(dockerHostEnv)
+			} else {
+				os.Unsetenv(dockerHostEnv)
+			}
+
+			got := tt.cfg.resolveDockerEndpoint()
+			if got != tt.expected {
+				t.Errorf("resolveDockerEndpoint() = %v, want %v, test: %s", got, tt.expected, tt.description)
+			}
+		})
+	}
+}
+
 func TestNewReceiver(t *testing.T) {
 	cfg := &Config{
 		ControllerConfig: scraperhelper.ControllerConfig{