Feat: HEALTH_ADDRESS_TO_PING variable

- Defaults to `1.1.1.1`
- Add more Ping integration tests with different addresses
- Add unit test pinging 127.0.0.1
- Add comment explaining why we need to use ICMP instead of UDP

internal/healthcheck/health_ping_test.go

@@ -5,6 +5,7 @@ package healthcheck
 import (
 	"context"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
 )
@@ -12,9 +13,34 @@ import (
 func Test_healthCheck_ping(t *testing.T) {
 	t.Parallel()
 
-	pinger := newPinger()
+	const timeout = time.Second
 
-	err := healthCheck(context.Background(), pinger)
+	testCases := map[string]struct {
+		address string
+		err     error
+	}{
+		"1.1.1.1": {
+			address: "1.1.1.1",
+		},
+		"99.99.99.99": {
+			address: "99.99.99.99",
+			err:     context.DeadlineExceeded,
+		},
+	}
 
-	assert.NoError(t, err)
+	for name, testCase := range testCases {
+		testCase := testCase
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			ctx, cancel := context.WithTimeout(context.Background(), timeout)
+			defer cancel()
+
+			pinger := newPinger(testCase.address)
+
+			err := healthCheck(ctx, pinger)
+
+			assert.ErrorIs(t, testCase.err, err)
+		})
+	}
 }

internal/healthcheck/health_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"testing"
+	"time"
 
 	"github.com/golang/mock/gomock"
 	"github.com/stretchr/testify/assert"
@@ -69,7 +70,7 @@ func Test_healthCheck(t *testing.T) {
 	t.Run("canceled real pinger", func(t *testing.T) {
 		t.Parallel()
 
-		pinger := newPinger()
+		pinger := newPinger("1.1.1.1")
 
 		canceledCtx, cancel := context.WithCancel(context.Background())
 		cancel()
@@ -78,4 +79,18 @@ func Test_healthCheck(t *testing.T) {
 
 		assert.ErrorIs(t, context.Canceled, err)
 	})
+
+	t.Run("ping 127.0.0.1", func(t *testing.T) {
+		t.Parallel()
+
+		pinger := newPinger("127.0.0.1")
+
+		const timeout = 100 * time.Millisecond
+		ctx, cancel := context.WithTimeout(context.Background(), timeout)
+		defer cancel()
+
+		err := healthCheck(ctx, pinger)
+
+		assert.NoError(t, err)
+	})
 }

internal/healthcheck/ping.go

@@ -9,11 +9,10 @@ type Pinger interface {
 	Stop()
 }
 
-func newPinger() (pinger *ping.Pinger) {
-	const addrToPing = "1.1.1.1"
+func newPinger(addrToPing string) (pinger *ping.Pinger) {
 	const count = 1
 	pinger = ping.New(addrToPing)
 	pinger.Count = count
-	pinger.SetPrivileged(true)
+	pinger.SetPrivileged(true) // see https://github.com/go-ping/ping#linux
 	return pinger
 }

internal/healthcheck/server.go

@@ -27,7 +27,7 @@ func NewServer(config configuration.Health,
 	return &Server{
 		logger:  logger,
 		handler: newHandler(logger),
-		pinger:  newPinger(),
+		pinger:  newPinger(config.AddressToPing),
 		config:  config,
 		vpn: vpnHealth{
 			looper:      vpnLooper,