fix(dns): fix slow dns resolution of localhost for grpc health probe

see: golang/go#35305

cmd/appregistry-server/main.go

@@ -12,6 +12,7 @@ import (
 	"github.com/operator-framework/operator-registry/pkg/api"
 	health "github.com/operator-framework/operator-registry/pkg/api/grpc_health_v1"
 	"github.com/operator-framework/operator-registry/pkg/appregistry"
+	"github.com/operator-framework/operator-registry/pkg/lib/dns"
 	"github.com/operator-framework/operator-registry/pkg/lib/log"
 	"github.com/operator-framework/operator-registry/pkg/registry"
 	"github.com/operator-framework/operator-registry/pkg/server"
@@ -61,6 +62,10 @@ func runCmdFunc(cmd *cobra.Command, args []string) error {
 	if err != nil {
 		logrus.WithError(err).Warn("unable to set termination log path")
 	}
+	// Ensure there is a default nsswitch config
+	if err := dns.EnsureNsswitch(); err != nil {
+		return err
+	}
 	kubeconfig, err := cmd.Flags().GetString("kubeconfig")
 	if err != nil {
 		return err

cmd/configmap-server/main.go

@@ -17,6 +17,7 @@ import (
 
 	"github.com/operator-framework/operator-registry/pkg/api"
 	health "github.com/operator-framework/operator-registry/pkg/api/grpc_health_v1"
+	"github.com/operator-framework/operator-registry/pkg/lib/dns"
 	"github.com/operator-framework/operator-registry/pkg/lib/log"
 	"github.com/operator-framework/operator-registry/pkg/registry"
 	"github.com/operator-framework/operator-registry/pkg/server"
@@ -67,6 +68,10 @@ func runCmdFunc(cmd *cobra.Command, args []string) error {
 	if err != nil {
 		logrus.WithError(err).Warn("unable to set termination log path")
 	}
+	// Ensure there is a default nsswitch config
+	if err := dns.EnsureNsswitch(); err != nil {
+		return err
+	}
 	kubeconfig, err := cmd.Flags().GetString("kubeconfig")
 	if err != nil {
 		return err

cmd/opm/registry/serve.go

@@ -13,6 +13,7 @@ import (
 
 	"github.com/operator-framework/operator-registry/pkg/api"
 	health "github.com/operator-framework/operator-registry/pkg/api/grpc_health_v1"
+	"github.com/operator-framework/operator-registry/pkg/lib/dns"
 	"github.com/operator-framework/operator-registry/pkg/lib/log"
 	"github.com/operator-framework/operator-registry/pkg/server"
 	"github.com/operator-framework/operator-registry/pkg/sqlite"
@@ -53,6 +54,12 @@ func serveFunc(cmd *cobra.Command, args []string) error {
 	if err != nil {
 		logrus.WithError(err).Warn("unable to set termination log path")
 	}
+
+	// Ensure there is a default nsswitch config
+	if err := dns.EnsureNsswitch(); err != nil {
+		return err
+	}
+
 	dbName, err := cmd.Flags().GetString("database")
 	if err != nil {
 		return err

cmd/registry-server/main.go

@@ -11,10 +11,10 @@ import (
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/reflection"
 
-	"github.com/operator-framework/operator-registry/pkg/lib/log"
-
 	"github.com/operator-framework/operator-registry/pkg/api"
 	health "github.com/operator-framework/operator-registry/pkg/api/grpc_health_v1"
+	"github.com/operator-framework/operator-registry/pkg/lib/dns"
+	"github.com/operator-framework/operator-registry/pkg/lib/log"
 	"github.com/operator-framework/operator-registry/pkg/server"
 	"github.com/operator-framework/operator-registry/pkg/sqlite"
 )
@@ -60,6 +60,10 @@ func runCmdFunc(cmd *cobra.Command, args []string) error {
 	if err != nil {
 		logrus.WithError(err).Warn("unable to set termination log path")
 	}
+	// Ensure there is a default nsswitch config
+	if err := dns.EnsureNsswitch(); err != nil {
+		return err
+	}
 	dbName, err := cmd.Flags().GetString("database")
 	if err != nil {
 		return err

pkg/lib/dns/nsswitch.go

@@ -0,0 +1,28 @@
+package dns
+
+import (
+	"io/ioutil"
+	"os"
+	"runtime"
+)
+
+var (
+	GOOS             = runtime.GOOS
+	NsswitchContents = []byte("hosts: files dns")
+	NsswitchFilename = "/etc/nsswitch.conf"
+)
+
+func EnsureNsswitch() error {
+	// only linux supports nsswitch
+	if GOOS != "linux" {
+		return nil
+	}
+
+	// if the file already exists, don't overwrite it
+	_, err := os.Stat(NsswitchFilename)
+	if !os.IsNotExist(err) {
+		return nil
+	}
+
+	return ioutil.WriteFile(NsswitchFilename, NsswitchContents, 0644)
+}

pkg/lib/dns/nsswitch_test.go

@@ -0,0 +1,73 @@
+package dns
+
+import (
+	"github.com/stretchr/testify/require"
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+func TestEnsureNsswitch(t *testing.T) {
+	tests := []struct {
+		name         string
+		goos         string
+		existingFile bool
+		wantFile     bool
+		wantErr      bool
+	}{
+		{
+			name:         "no file",
+			goos:         "linux",
+			existingFile: false,
+			wantFile:     true,
+			wantErr:      false,
+		},
+		{
+			name:         "existing file",
+			goos:         "linux",
+			existingFile: true,
+			wantFile:     false,
+			wantErr:      false,
+		},
+		{
+			name:     "windows",
+			goos:     "windows",
+			wantFile: false,
+			wantErr:  false,
+		},
+		{
+			name:     "mac",
+			goos:     "darwin",
+			wantFile: false,
+			wantErr:  false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			GOOS = tt.goos
+			// don't want to overwrite the real nsswitch
+			NsswitchFilename = "testfile"
+
+			if tt.existingFile {
+				require.NoError(t, ioutil.WriteFile(NsswitchFilename, []byte("test"), 0644))
+			}
+
+			if err := EnsureNsswitch(); (err != nil) != tt.wantErr {
+				t.Errorf("EnsureNsswitch() error = %v, wantErr %v", err, tt.wantErr)
+			}
+
+			if tt.wantFile {
+				contents, err := ioutil.ReadFile(NsswitchFilename)
+				require.NoError(t, err)
+				require.Equal(t, NsswitchContents, contents)
+				os.Remove(NsswitchFilename)
+			}
+			if tt.existingFile {
+				contents, err := ioutil.ReadFile(NsswitchFilename)
+				require.NoError(t, err)
+				require.NotEqual(t, NsswitchContents, contents)
+				os.Remove(NsswitchFilename)
+			}
+		})
+	}
+}