Gracefully handle Temporary errors from Accept()

This should prevent the Cloud SQL proxy from dying once it e.g. hits the
max filedescriptor limit.

Author: Jille

cmd/cloud_sql_proxy/proxy.go

@@ -142,6 +142,9 @@ func listenInstance(dst chan<- proxy.Conn, cfg instanceConfig) (net.Listener, er
 			c, err := l.Accept()
 			if err != nil {
 				logging.Errorf("Error in accept for %q on %v: %v", cfg, cfg.Address, err)
+				if nerr, ok := err.(net.Error); ok && nerr.Temporary() {
+					continue
+				}
 				l.Close()
 				return
 			}

proxy/fuse/fuse.go

@@ -284,6 +284,9 @@ func (r *fsRoot) listenerLifecycle(l net.Listener, instance, path string) {
 		c, err := l.Accept()
 		if err != nil {
 			logging.Errorf("error in Accept for %q: %v", instance, err)
+			if nerr, ok := err.(net.Error); ok && nerr.Temporary() {
+				continue
+			}
 			break
 		}
 		r.newConn(instance, c)

proxy/proxy/client.go

@@ -271,6 +271,9 @@ func NewConnSrc(instance string, l net.Listener) <-chan Conn {
 			c, err := l.Accept()
 			if err != nil {
 				logging.Errorf("listener (%#v) had error: %v", l, err)
+				if nerr, ok := err.(net.Error); ok && nerr.Temporary() {
+					continue
+				}
 				l.Close()
 				close(ch)
 				return