fix race condition

Signed-off-by: Mohammed Al Sahaf <msaa1990@gmail.com>

modules/logging/netwriter.go

@@ -67,6 +67,7 @@ type NetWriter struct {
 	flushWg             sync.WaitGroup
 	lastProcessedOffset int64
 	mu                  sync.RWMutex
+	walMu               sync.Mutex // synchronizes WAL read/write operations
 }
 
 // CaddyModule returns the Caddy module information.
@@ -193,7 +194,7 @@ func (nw *NetWriter) loadLastProcessedOffset() {
 // saveLastProcessedOffset saves the last processed offset to a metadata file
 func (nw *NetWriter) saveLastProcessedOffset(cp *wal.ChunkPosition) {
 	// Create a unique offset by combining segment, block, and chunk offset
-	offset := (int64(cp.SegmentId) << 32) | (int64(cp.BlockNumber) << 16) | int64(cp.ChunkOffset)
+	offset := (int64(cp.SegmentId) << 32) | (int64(cp.BlockNumber) << 16) | (cp.ChunkOffset)
 
 	nw.mu.Lock()
 	nw.lastProcessedOffset = offset
@@ -314,14 +315,20 @@ func (nw *NetWriter) backgroundFlusher() {
 
 // processWALEntries processes all available entries in the WAL using a fresh reader
 func (nw *NetWriter) processWALEntries(writeToConn func([]byte) error) {
+	// Synchronize WAL access to prevent race conditions with writers
+	nw.walMu.Lock()
 	// Create a fresh reader to see all current entries
 	reader := nw.wal.NewReader()
+	nw.walMu.Unlock()
 
 	processed := 0
 	skipped := 0
 	nw.logger.Debug("processing available WAL entries")
 	for {
+		nw.walMu.Lock()
 		data, cp, err := reader.Next()
+		nw.walMu.Unlock()
+
 		if err == io.EOF {
 			if processed > 0 {
 				nw.logger.Debug("processed WAL entries", "processed", processed, "skipped", skipped)
@@ -343,7 +350,7 @@ func (nw *NetWriter) processWALEntries(writeToConn func([]byte) error) {
 		nw.mu.RUnlock()
 
 		// Create current entry offset for comparison
-		currentOffset := (int64(cp.SegmentId) << 32) | (int64(cp.BlockNumber) << 16) | int64(cp.ChunkOffset)
+		currentOffset := (int64(cp.SegmentId) << 32) | (int64(cp.BlockNumber) << 16) | (cp.ChunkOffset)
 		nw.logger.Debug("found WAL entry", "segmentId", cp.SegmentId, "blockNumber", cp.BlockNumber, "chunkOffset", cp.ChunkOffset, "currentOffset", currentOffset, "lastProcessedOffset", lastProcessedOffset, "size", len(data))
 
 		if currentOffset <= lastProcessedOffset {
@@ -380,12 +387,18 @@ func (nw *NetWriter) processWALEntry(data []byte, cp *wal.ChunkPosition, writeTo
 func (nw *NetWriter) flushRemainingWALEntries(writeToConn func([]byte) error) {
 	nw.logger.Info("flushing remaining WAL entries during shutdown")
 
+	// Synchronize WAL access to prevent race conditions with writers
+	nw.walMu.Lock()
 	// Create a fresh reader for shutdown processing
 	reader := nw.wal.NewReader()
+	nw.walMu.Unlock()
 
 	count := 0
 	for {
+		nw.walMu.Lock()
 		data, cp, err := reader.Next()
+		nw.walMu.Unlock()
+
 		if err == io.EOF {
 			break
 		}
@@ -400,7 +413,7 @@ func (nw *NetWriter) flushRemainingWALEntries(writeToConn func([]byte) error) {
 		nw.mu.RUnlock()
 
 		// Create current entry offset for comparison
-		currentOffset := (int64(cp.SegmentId) << 32) | (int64(cp.BlockNumber) << 16) | int64(cp.ChunkOffset)
+		currentOffset := (int64(cp.SegmentId) << 32) | (int64(cp.BlockNumber) << 16) | (cp.ChunkOffset)
 
 		if currentOffset <= lastProcessedOffset {
 			// Already processed, skip
@@ -446,6 +459,10 @@ func (w *netWriterConn) Write(p []byte) (n int, err error) {
 
 	w.nw.logger.Debug("writing to WAL", "size", len(p))
 
+	// Synchronize WAL access to prevent race conditions
+	w.nw.walMu.Lock()
+	defer w.nw.walMu.Unlock()
+
 	// Write to WAL - this should be fast and non-blocking
 	_, err = w.nw.wal.Write(p)
 	if err != nil {
@@ -473,14 +490,16 @@ func (w *netWriterConn) Close() error {
 
 	var errs []error
 
-	// Sync and close WAL
+	// Sync and close WAL with synchronization
 	if w.nw.wal != nil {
+		w.nw.walMu.Lock()
 		if err := w.nw.wal.Sync(); err != nil {
 			errs = append(errs, fmt.Errorf("WAL sync error: %v", err))
 		}
 		if err := w.nw.wal.Close(); err != nil {
 			errs = append(errs, fmt.Errorf("WAL close error: %v", err))
 		}
+		w.nw.walMu.Unlock()
 	}
 
 	if len(errs) > 0 {

modules/logging/netwriter_test.go

@@ -885,7 +885,8 @@ func TestNetWriter_UnmarshalCaddyfile(t *testing.T) {
 		},
 	}
 
-	for _, tt := range tests {
+	for i := range tests {
+		tt := tests[i] //nolint:copylocks
 		t.Run(tt.name, func(t *testing.T) {
 			d := caddyfile.NewTestDispenser(tt.input)
 			nw := &NetWriter{}