From b66030eff89f06d7db43becab989327567f377ca Mon Sep 17 00:00:00 2001
From: lysu <sulifx@gmail.com>
Date: Fri, 25 Oct 2019 14:32:29 +0800
Subject: [PATCH] server: log last executed prepared stmt when panic (#12905)

---
 server/conn.go      | 42 +++++++++++++++++++++++++++++++++++++-----
 server/conn_stmt.go |  3 +++
 2 files changed, 40 insertions(+), 5 deletions(-)

diff --git a/server/conn.go b/server/conn.go
index 4ae0b0a145c2f..3f570c6d9a6a6 100644
--- a/server/conn.go
+++ b/server/conn.go
@@ -144,7 +144,7 @@ type clientConn struct {
 	dbname       string            // default database name.
 	salt         []byte            // random bytes used for authentication.
 	alloc        arena.Allocator   // an memory allocator for reducing memory allocation.
-	lastCmd      string            // latest sql query string, currently used for logging error.
+	lastPacket   []byte            // latest sql query string, currently used for logging error.
 	ctx          QueryCtx          // an interface to execute sql statements.
 	attrs        map[string]string // attributes parsed from client handshake response, not used for now.
 	status       int32             // dispatching/reading/shutdown/waitshutdown
@@ -612,7 +612,7 @@ func (cc *clientConn) Run(ctx context.Context) {
 			stackSize := runtime.Stack(buf, false)
 			buf = buf[:stackSize]
 			logutil.Logger(ctx).Error("connection running loop panic",
-				zap.String("lastCmd", cc.lastCmd),
+				zap.Stringer("lastSQL", getLastStmtInConn{cc}),
 				zap.Reflect("err", r),
 				zap.String("stack", string(buf)),
 			)
@@ -683,7 +683,7 @@ func (cc *clientConn) Run(ctx context.Context) {
 				zap.String("connInfo", cc.String()),
 				zap.String("command", mysql.Command2Str[data[0]]),
 				zap.String("status", cc.SessionStatusToString()),
-				zap.String("sql", queryStrForLog(string(data[1:]))),
+				zap.Stringer("sql", getLastStmtInConn{cc}),
 				zap.String("err", errStrForLog(err)),
 			)
 			err1 := cc.writeError(err)
@@ -864,9 +864,9 @@ func (cc *clientConn) dispatch(ctx context.Context, data []byte) error {
 	span := opentracing.StartSpan("server.dispatch")
 
 	t := time.Now()
+	cc.lastPacket = data
 	cmd := data[0]
 	data = data[1:]
-	cc.lastCmd = string(hack.String(data))
 	token := cc.server.getToken()
 	defer func() {
 		// if handleChangeUser failed, cc.ctx may be nil
@@ -1285,7 +1285,7 @@ func (cc *clientConn) writeResultset(ctx context.Context, rs ResultSet, binary b
 		buf := make([]byte, 4096)
 		stackSize := runtime.Stack(buf, false)
 		buf = buf[:stackSize]
-		logutil.Logger(ctx).Error("write query result panic", zap.String("lastCmd", cc.lastCmd), zap.String("stack", string(buf)))
+		logutil.Logger(ctx).Error("write query result panic", zap.Stringer("lastSQL", getLastStmtInConn{cc}), zap.String("stack", string(buf)))
 	}()
 	var err error
 	if mysql.HasCursorExistsFlag(serverStatus) {
@@ -1515,3 +1515,35 @@ func (cc *clientConn) handleChangeUser(ctx context.Context, data []byte) error {
 
 	return cc.writeOK()
 }
+
+var _ fmt.Stringer = getLastStmtInConn{}
+
+type getLastStmtInConn struct {
+	*clientConn
+}
+
+func (cc getLastStmtInConn) String() string {
+	if len(cc.lastPacket) == 0 {
+		return ""
+	}
+	cmd, data := cc.lastPacket[0], cc.lastPacket[1:]
+	switch cmd {
+	case mysql.ComInitDB:
+		return "Use " + string(data)
+	case mysql.ComFieldList:
+		return "ListFields " + string(data)
+	case mysql.ComQuery, mysql.ComStmtPrepare:
+		return queryStrForLog(string(hack.String(data)))
+	case mysql.ComStmtExecute, mysql.ComStmtFetch:
+		stmtID := binary.LittleEndian.Uint32(data[0:4])
+		return queryStrForLog(cc.preparedStmt2String(stmtID))
+	case mysql.ComStmtClose, mysql.ComStmtReset:
+		stmtID := binary.LittleEndian.Uint32(data[0:4])
+		return mysql.Command2Str[cmd] + " " + strconv.Itoa(int(stmtID))
+	default:
+		if cmdStr, ok := mysql.Command2Str[cmd]; ok {
+			return cmdStr
+		}
+		return string(hack.String(data))
+	}
+}
diff --git a/server/conn_stmt.go b/server/conn_stmt.go
index b4b1ebcfd0ef6..5669074a732a6 100644
--- a/server/conn_stmt.go
+++ b/server/conn_stmt.go
@@ -581,6 +581,9 @@ func (cc *clientConn) handleSetOption(data []byte) (err error) {
 
 func (cc *clientConn) preparedStmt2String(stmtID uint32) string {
 	sv := cc.ctx.GetSessionVars()
+	if sv == nil {
+		return ""
+	}
 	if prepared, ok := sv.PreparedStmts[stmtID]; ok {
 		return prepared.Stmt.Text() + sv.PreparedParams.String()
 	}