proxy: Added a connectivity test on startup that will test if the ins…

…tances are reachable

README.md

@@ -36,6 +36,8 @@ cloud_sql_proxy takes a few arguments to configure what instances to connect to
   down the proxy. Defaults to 0.
 * `-skip_failed_instance_config`: Setting this flag will allow you to prevent the proxy from terminating when
 	some instance configurations could not be parsed and/or are unavailable.
+* `-perform_connectivity_tests`: Performs connectivity tests on startup to the
+  databases and exits the proxy if one of them fails.
 
 Note: `-instances` and `-instances_metadata` may be used at the same time but
 are not compatible with the `-fuse` flag.

cmd/cloud_sql_proxy/cloud_sql_proxy.go

@@ -73,7 +73,8 @@ to use the instance metadata value named 'cloud-sql-instances' you would
 provide 'instance/attributes/cloud-sql-instances'. Not compatible with -fuse`)
 	useFuse = flag.Bool("fuse", false, `Mount a directory at 'dir' using FUSE for accessing instances. Note that the
 directory at 'dir' must be empty before this program is started.`)
-	fuseTmp = flag.String("fuse_tmp", defaultTmp, `Used as a temporary directory if -fuse is set. Note that files in this directory
+	performConnectivityTestsOnStartup = flag.Bool("perform_connectivity_tests", false, `Performs connectivity tests on startup to the databases and exits the proxy if one of them fails.`)
+	fuseTmp                           = flag.String("fuse_tmp", defaultTmp, `Used as a temporary directory if -fuse is set. Note that files in this directory
 can be removed automatically by this program.`)
 
 	// Settings for limits
@@ -324,6 +325,27 @@ func stringList(s string) []string {
 	return spl
 }
 
+func checkInstanceConnectivity(instanceName string, public bool, client *proxy.Client) error {
+	// The connectivity test right now is just a basic dial to make sure it is reachable
+	// and nothing more. This will help rule out basic network connectivity problems, though
+	// such as firewalls and the like.
+	conn, err := client.Dial(instanceName)
+
+	if conn != nil {
+		conn.Close()
+	}
+
+	if err != nil {
+		if public {
+			return fmt.Errorf("Performed connectivity test to public instance %v and got an error: %v. Do you have a route to it?", instanceName, err)
+		} else {
+			return fmt.Errorf("Performed connectivity test to private instance %v and got an error: %v. Do you have a route to it?", instanceName, err)
+		}
+	}
+
+	return nil
+}
+
 func listInstances(ctx context.Context, cl *http.Client, projects []string) ([]string, error) {
 	if len(projects) == 0 {
 		// No projects requested.
@@ -524,7 +546,6 @@ func main() {
 	if refreshCfgThrottle < minimumRefreshCfgThrottle {
 		refreshCfgThrottle = minimumRefreshCfgThrottle
 	}
-	logging.Infof("Ready for new connections")
 
 	proxyClient := &proxy.Client{
 		Port:           port,
@@ -539,6 +560,26 @@ func main() {
 		RefreshCfgThrottle: refreshCfgThrottle,
 	}
 
+	if *performConnectivityTestsOnStartup {
+		wg := &sync.WaitGroup{}
+		wg.Add(len(cfgs))
+
+		for index, instanceConfig := range cfgs {
+			logging.Infof("Checking connection to instance %s...", instanceConfig.Instance)
+			go func(index int, instance string, isPublic bool, client *proxy.Client) {
+				defer wg.Done()
+				err := checkInstanceConnectivity(instance, isPublic, client)
+
+				if err != nil {
+					log.Fatalf("%v", instance, err)
+				}
+			}(index, instanceConfig.Instance, instanceConfig.IsPublic, proxyClient)
+		}
+		wg.Wait()
+	}
+
+	logging.Infof("Ready for new connections")
+
 	signals := make(chan os.Signal, 1)
 	signal.Notify(signals, syscall.SIGTERM, syscall.SIGINT)
 

cmd/cloud_sql_proxy/proxy.go

@@ -177,6 +177,7 @@ func listenInstance(dst chan<- proxy.Conn, cfg instanceConfig) (net.Listener, er
 type instanceConfig struct {
 	Instance         string
 	Network, Address string
+	IsPublic         bool
 }
 
 // loopbackForNet maps a network (e.g. tcp6) to the loopback address for that
@@ -273,6 +274,15 @@ func parseInstanceConfig(dir, instance string, cl *http.Client) (instanceConfig,
 	if err != nil {
 		return instanceConfig{}, err
 	}
+
+	// Check to see if one of the addresses is public or not
+	// and mark that on the config
+	for _, mapping := range inst.IpAddresses {
+		if mapping.Type == "PRIMARY" {
+			ret.IsPublic = true
+		}
+	}
+
 	if inst.BackendType == "FIRST_GEN" {
 		logging.Errorf("WARNING: proxy client does not support first generation Cloud SQL instances.")
 		return instanceConfig{}, fmt.Errorf("%q is a first generation instance", instance)