Code review fixes

pkg/wal/iterator.go

@@ -91,7 +91,7 @@ func (b *segmentIterator) Next() (bool, error) {
 }
 
 func (b *segmentIterator) nextValue() (bool, error) {
-	if b.n > len(b.buf) {
+	if b.n >= len(b.buf) {
 		return false, io.EOF
 	}
 	blockLen := binary.BigEndian.Uint32(b.buf[b.n : b.n+4])

pkg/wal/segment.go

@@ -285,7 +285,7 @@ func (s *segment) Close() error {
 	return s.w.Close()
 }
 
-// repair truncates the last bytes in the segment if they don't are missing, corrupted or have extra data.  This
+// repair truncates the last bytes in the segment if they are missing, corrupted or have extra data.  This
 // repairs any corrupted segment that may not have fully flushed to disk safely.
 func (s *segment) repair() error {
 	buf := make([]byte, 0, 4096)
@@ -304,6 +304,7 @@ func (s *segment) repair() error {
 		idx += n
 
 		if err != nil || n != 8 {
+			logger.Warn("Repairing segment %s, missing block header, truncating at %d", s.path, lastGoodIdx)
 			return s.truncate(int64(lastGoodIdx))
 		}
 
@@ -321,10 +322,12 @@ func (s *segment) repair() error {
 		}
 
 		if uint32(n) != blockLen {
+			logger.Warn("Repairing segment %s, short block, truncating at %d", s.path, lastGoodIdx)
 			return s.truncate(int64(lastGoodIdx))
 		}
 
 		if crc32.ChecksumIEEE(buf[:blockLen]) != crc {
+			logger.Warn("Repairing segment %s, checksum failed, truncating at %d", s.path, lastGoodIdx)
 			return s.truncate(int64(lastGoodIdx))
 		}
 

tools/cmd/walreader/main.go

@@ -1,9 +1,7 @@
 package main
 
 import (
-	"bytes"
 	"flag"
-	"io"
 	"os"
 
 	"github.com/Azure/adx-mon/pkg/logger"
@@ -39,23 +37,4 @@ func main() {
 		}
 		print(string(iter.Value()))
 	}
-
-	return
-	reader, err := wal.NewSegmentReader(dataFile)
-	if err != nil {
-		logger.Fatal("open file: %s", err)
-	}
-
-	defer reader.Close()
-
-	b, err := io.ReadAll(reader)
-	if err != nil {
-		// logger.Fatal("read: %s", err)
-	}
-
-	lines := bytes.Split(b, []byte("\n"))
-	for _, line := range lines {
-		println(string(line))
-	}
-
 }