From 802a94cfc55bca4078c82f53dbd88b3b91f74d09 Mon Sep 17 00:00:00 2001
From: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>
Date: Thu, 19 Oct 2023 16:39:12 +0300
Subject: [PATCH] simplified synchronization logic; temporary logging

Signed-off-by: Shlomi Noach <2607934+shlomi-noach@users.noreply.github.com>
---
 go/vt/mysqlctl/mysqld.go | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/go/vt/mysqlctl/mysqld.go b/go/vt/mysqlctl/mysqld.go
index ba4ccf755b3..19ee1b2574a 100644
--- a/go/vt/mysqlctl/mysqld.go
+++ b/go/vt/mysqlctl/mysqld.go
@@ -1323,7 +1323,17 @@ func parseBinlogEntryTimestamp(logEntry string) (found bool, t time.Time, err er
 
 // scanBinlogTimestamp invokes a `mysqlbinlog` binary to look for a timestamp in the given binary. The function
 // either looks for the first such timestamp or the last.
-func (mysqld *Mysqld) scanBinlogTimestamp(mysqlbinlogDir string, mysqlbinlogEnv []string, mysqlbinlogName string, binlogFile string, stopAtFirst bool) (matchedTime time.Time, matchFound bool, err error) {
+func (mysqld *Mysqld) scanBinlogTimestamp(
+	mysqlbinlogDir string,
+	mysqlbinlogEnv []string,
+	mysqlbinlogName string,
+	binlogFile string,
+	stopAtFirst bool,
+) (
+	matchedTime time.Time,
+	matchFound bool,
+	err error,
+) {
 	args := []string{binlogFile}
 	mysqlbinlogCmd := exec.Command(mysqlbinlogName, args...)
 	mysqlbinlogCmd.Dir = mysqlbinlogDir
@@ -1333,10 +1343,12 @@ func (mysqld *Mysqld) scanBinlogTimestamp(mysqlbinlogDir string, mysqlbinlogEnv
 	if err != nil {
 		return matchedTime, false, err
 	}
-	scanComplete := make(chan error)
+	var scanError error
 	intentionalKill := false
+	var wg sync.WaitGroup
+	wg.Add(1)
 	scan := func() {
-		defer close(scanComplete)
+		defer wg.Done()
 		defer func() {
 			intentionalKill = true
 			mysqlbinlogCmd.Process.Kill() // ensures the binlog file is released
@@ -1348,7 +1360,7 @@ func (mysqld *Mysqld) scanBinlogTimestamp(mysqlbinlogDir string, mysqlbinlogEnv
 
 			found, t, err := parseBinlogEntryTimestamp(logEntry)
 			if err != nil {
-				scanComplete <- err
+				scanError = err
 				return
 			}
 			if found {
@@ -1369,7 +1381,8 @@ func (mysqld *Mysqld) scanBinlogTimestamp(mysqlbinlogDir string, mysqlbinlogEnv
 	if err := mysqlbinlogCmd.Wait(); err != nil && !intentionalKill {
 		return matchedTime, false, vterrors.Wrapf(err, "waiting on mysqlbinlog command in ReadBinlogFilesTimestamps")
 	}
-	if err := <-scanComplete; err != nil {
+	wg.Wait()
+	if scanError != nil {
 		return matchedTime, false, vterrors.Wrapf(err, "scanning mysqlbinlog output in ReadBinlogFilesTimestamps	")
 	}
 	return matchedTime, matchFound, nil
@@ -1407,26 +1420,30 @@ func (mysqld *Mysqld) ReadBinlogFilesTimestamps(ctx context.Context, req *mysqlc
 	for _, binlogFile := range req.BinlogFileNames {
 		t, found, err := mysqld.scanBinlogTimestamp(dir, env, mysqlbinlogName, binlogFile, true)
 		if err != nil {
-			return nil, err
+			return nil, vterrors.Wrapf(err, "while scanning for first binlog timestamp in %v", binlogFile)
 		}
 		if found {
+			log.Errorf("==== QQQ found first timestamp in binlog file: %v", binlogFile)
 			resp.FirstTimestamp = protoutil.TimeToProto(t)
 			resp.FirstTimestampBinlog = binlogFile
 			break
 		}
+		log.Errorf("==== QQQ could not find first timestamp in binlog file: %v", binlogFile)
 	}
 	// Find last timestamp
 	for i := len(req.BinlogFileNames) - 1; i >= 0; i-- {
 		binlogFile := req.BinlogFileNames[i]
 		t, found, err := mysqld.scanBinlogTimestamp(dir, env, mysqlbinlogName, binlogFile, false)
 		if err != nil {
-			return nil, err
+			return nil, vterrors.Wrapf(err, "while scanning for last binlog timestamp in %v", binlogFile)
 		}
 		if found {
+			log.Errorf("==== QQQ found last timestamp in binlog file: %v", binlogFile)
 			resp.LastTimestamp = protoutil.TimeToProto(t)
 			resp.LastTimestampBinlog = binlogFile
 			break
 		}
+		log.Errorf("==== QQQ could not find first timestamp in binlog file: %v", binlogFile)
 	}
 	return resp, nil
 }