From ddf7bfb748d46ee2c888417f96ac8a783fc4756d Mon Sep 17 00:00:00 2001
From: djshow832 <zhangming@pingcap.com>
Date: Mon, 5 Sep 2022 12:49:23 +0800
Subject: [PATCH] backend: fix the bug that the redirection signal may be
 discarded (#75)

---
 pkg/proxy/backend/backend_conn_mgr.go | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/pkg/proxy/backend/backend_conn_mgr.go b/pkg/proxy/backend/backend_conn_mgr.go
index aeb63e2a..158da8f9 100644
--- a/pkg/proxy/backend/backend_conn_mgr.go
+++ b/pkg/proxy/backend/backend_conn_mgr.go
@@ -88,7 +88,7 @@ func NewBackendConnManager(connectionID uint64) *BackendConnManager {
 		connectionID:   connectionID,
 		cmdProcessor:   NewCmdProcessor(),
 		authenticator:  &Authenticator{},
-		signalReceived: make(chan struct{}),
+		signalReceived: make(chan struct{}, 1),
 		redirectResCh:  make(chan *redirectResult, 1),
 	}
 }
@@ -292,10 +292,8 @@ func (mgr *BackendConnManager) Redirect(newAddr string) {
 	atomic.StorePointer(&mgr.signal, unsafe.Pointer(&signalRedirect{
 		newAddr: newAddr,
 	}))
-	select {
-	case mgr.signalReceived <- struct{}{}:
-	default:
-	}
+	// Generally, it won't wait because the caller won't send another signal because the last one finishes.
+	mgr.signalReceived <- struct{}{}
 }
 
 // GetRedirectingAddr implements RedirectableConn.GetRedirectingAddr interface.