fix: let proxy continue to run with inactive instance(s) (#1854)

Replaced fmt.Errorf with logger.Errorf for instance failure

Fail the inactive instance with unix path

Fixed lint error

Added inactive instance test with unix path

Replace getNetworkType with networkType

Fixed the error path indentation

Make the unix path failure test a seperate func

internal/proxy/proxy.go

@@ -510,19 +510,19 @@ func NewClient(ctx context.Context, d cloudsql.Dialer, l cloudsql.Logger, conf *
 	for _, inst := range conf.Instances {
 		m, err := c.newSocketMount(ctx, conf, pc, inst)
 		if err != nil {
-			for _, m := range mnts {
-				mErr := m.Close()
-				if mErr != nil {
-					l.Errorf("failed to close mount: %v", mErr)
-				}
+			c.logger.Errorf("[%v] Unable to mount socket: %v", inst.Name, err)
+			if networkType(conf, inst) == "unix" {
+				continue
 			}
-			return nil, fmt.Errorf("[%v] Unable to mount socket: %v", inst.Name, err)
 		}
 
 		l.Infof("[%s] Listening on %s", inst.Name, m.Addr())
 		mnts = append(mnts, m)
 	}
 	c.mnts = mnts
+	if len(mnts) == 0 {
+		return nil, fmt.Errorf("No active instance to mount")
+	}
 	return c, nil
 }
 
@@ -747,6 +747,14 @@ type socketMount struct {
 	dialOpts []cloudsqlconn.DialOption
 }
 
+func networkType(conf *Config, inst InstanceConnConfig) string {
+	if (conf.UnixSocket == "" && inst.UnixSocket == "" && inst.UnixSocketPath == "") ||
+		(inst.Addr != "" || inst.Port != 0) {
+		return "tcp"
+	}
+	return "unix"
+}
+
 func (c *Client) newSocketMount(ctx context.Context, conf *Config, pc *portConfig, inst InstanceConnConfig) (*socketMount, error) {
 	var (
 		// network is one of "tcp" or "unix"
@@ -765,8 +773,7 @@ func (c *Client) newSocketMount(ctx context.Context, conf *Config, pc *portConfi
 	//   instance)
 	// use a TCP listener.
 	// Otherwise, use a Unix socket.
-	if (conf.UnixSocket == "" && inst.UnixSocket == "" && inst.UnixSocketPath == "") ||
-		(inst.Addr != "" || inst.Port != 0) {
+	if networkType(conf, inst) == "tcp" {
 		network = "tcp"
 
 		a := conf.Addr
@@ -784,7 +791,6 @@ func (c *Client) newSocketMount(ctx context.Context, conf *Config, pc *portConfi
 			version, err := c.dialer.EngineVersion(ctx, inst.Name)
 			if err != nil {
 				c.logger.Errorf("could not resolve version for %q: %v", inst.Name, err)
-				return nil, err
 			}
 			np = pc.nextDBPort(version)
 		}
@@ -801,6 +807,8 @@ func (c *Client) newSocketMount(ctx context.Context, conf *Config, pc *portConfi
 
 		address, err = newUnixSocketMount(inst, conf.UnixSocket, strings.HasPrefix(version, "POSTGRES"))
 		if err != nil {
+			c.logger.Errorf("could not mount unix socket %q for %q: %v",
+				conf.UnixSocket, inst.Name, err)
 			return nil, err
 		}
 	}

internal/proxy/proxy_test.go

@@ -17,6 +17,7 @@ package proxy_test
 import (
 	"context"
 	"errors"
+	"fmt"
 	"io"
 	"net"
 	"os"
@@ -83,6 +84,8 @@ func (f *fakeDialer) EngineVersion(_ context.Context, inst string) (string, erro
 		return "MYSQL_8_0", nil
 	case strings.Contains(inst, "sqlserver"):
 		return "SQLSERVER_2019_STANDARD", nil
+	case strings.Contains(inst, "fakeserver"):
+		return "", fmt.Errorf("non existing server")
 	default:
 		return "POSTGRES_14", nil
 	}
@@ -306,6 +309,25 @@ func TestClientInitialization(t *testing.T) {
 				filepath.Join(testUnixSocketPathPg),
 			},
 		},
+		{
+			desc: "without TCP port or unix socket for non functional instance",
+			in: &proxy.Config{
+				Instances: []proxy.InstanceConnConfig{
+					{Name: "proj:region:fakeserver"},
+				},
+			},
+		},
+		{
+			desc: "with TCP port for non functional instance",
+			in: &proxy.Config{
+				Instances: []proxy.InstanceConnConfig{
+					{Name: "proj:region:fakeserver", Port: 50000},
+				},
+			},
+			wantTCPAddrs: []string{
+				"127.0.0.1:50000",
+			},
+		},
 	}
 
 	for _, tc := range tcs {
@@ -711,3 +733,34 @@ func TestRunConnectionCheck(t *testing.T) {
 	}
 
 }
+
+func TestProxyInitializationWithFailedUnixSocket(t *testing.T) {
+	ctx := context.Background()
+	testDir, _ := createTempDir(t)
+	testUnixSocketPath := path.Join(testDir, "db")
+
+	tcs := []struct {
+		desc string
+		in   *proxy.Config
+	}{
+		{
+			desc: "with unix socket for non functional instance",
+			in: &proxy.Config{
+				Instances: []proxy.InstanceConnConfig{
+					{
+						Name:           "proj:region:fakeserver",
+						UnixSocketPath: testUnixSocketPath,
+					},
+				},
+			},
+		},
+	}
+	for _, tc := range tcs {
+		t.Run(tc.desc, func(t *testing.T) {
+			_, err := proxy.NewClient(ctx, &fakeDialer{}, testLogger, tc.in)
+			if err == nil {
+				t.Fatalf("want non nil error, got = %v", err)
+			}
+		})
+	}
+}