wal: Replace promauto with injected registry

Signed-off-by: Frederic Branczyk <fbranczyk@gmail.com>

wal/live_reader.go

@@ -24,19 +24,11 @@ import (
 	"github.com/go-kit/kit/log/level"
 	"github.com/pkg/errors"
 	"github.com/prometheus/client_golang/prometheus"
-	"github.com/prometheus/client_golang/prometheus/promauto"
-)
-
-var (
-	readerCorruptionErrors = promauto.NewCounterVec(prometheus.CounterOpts{
-		Name: "prometheus_tsdb_wal_reader_corruption_errors",
-		Help: "Errors encountered when reading the WAL.",
-	}, []string{"error"})
 )
 
 // NewLiveReader returns a new live reader.
-func NewLiveReader(logger log.Logger, r io.Reader) *LiveReader {
-	return &LiveReader{
+func NewLiveReader(logger log.Logger, reg prometheus.Registerer, r io.Reader) *LiveReader {
+	lr := &LiveReader{
 		logger: logger,
 		rdr:    r,
 
@@ -44,6 +36,17 @@ func NewLiveReader(logger log.Logger, r io.Reader) *LiveReader {
 		// to records spanning pages.
 		permissive: true,
 	}
+
+	lr.readerCorruptionErrors = prometheus.NewCounterVec(prometheus.CounterOpts{
+		Name: "prometheus_tsdb_wal_reader_corruption_errors",
+		Help: "Errors encountered when reading the WAL.",
+	}, []string{"error"})
+
+	if reg != nil {
+		reg.MustRegister(lr.readerCorruptionErrors)
+	}
+
+	return lr
 }
 
 // LiveReader reads WAL records from an io.Reader. It allows reading of WALs
@@ -68,6 +71,8 @@ type LiveReader struct {
 	// does.  Until we track down why, set permissive to true to tolerate it.
 	// NB the non-ive Reader implementation allows for this.
 	permissive bool
+
+	readerCorruptionErrors *prometheus.CounterVec
 }
 
 // Err returns any errors encountered reading the WAL.  io.EOFs are not terminal
@@ -258,7 +263,7 @@ func (r *LiveReader) readRecord() ([]byte, int, error) {
 		if !r.permissive {
 			return nil, 0, fmt.Errorf("record would overflow current page: %d > %d", r.readIndex+recordHeaderSize+length, pageSize)
 		}
-		readerCorruptionErrors.WithLabelValues("record_span_page").Inc()
+		r.readerCorruptionErrors.WithLabelValues("record_span_page").Inc()
 		level.Warn(r.logger).Log("msg", "record spans page boundaries", "start", r.readIndex, "end", recordHeaderSize+length, "pageSize", pageSize)
 	}
 	if recordHeaderSize+length > pageSize {

wal/reader_test.go

@@ -51,7 +51,7 @@ var readerConstructors = map[string]func(io.Reader) reader{
 		return NewReader(r)
 	},
 	"LiveReader": func(r io.Reader) reader {
-		lr := NewLiveReader(log.NewNopLogger(), r)
+		lr := NewLiveReader(log.NewNopLogger(), nil, r)
 		lr.eofNonErr = true
 		return lr
 	},
@@ -216,7 +216,7 @@ func TestReader_Live(t *testing.T) {
 			// Read from a second FD on the same file.
 			readFd, err := os.Open(writeFd.Name())
 			testutil.Ok(t, err)
-			reader := NewLiveReader(logger, readFd)
+			reader := NewLiveReader(logger, nil, readFd)
 			for _, exp := range testReaderCases[i].exp {
 				for !reader.Next() {
 					testutil.Assert(t, reader.Err() == io.EOF, "expect EOF, got: %v", reader.Err())
@@ -374,7 +374,7 @@ func TestReaderFuzz_Live(t *testing.T) {
 	testutil.Ok(t, err)
 	defer seg.Close()
 
-	r := NewLiveReader(logger, seg)
+	r := NewLiveReader(logger, nil, seg)
 	segmentTicker := time.NewTicker(100 * time.Millisecond)
 	readTicker := time.NewTicker(10 * time.Millisecond)
 
@@ -410,7 +410,7 @@ outer:
 			seg, err = OpenReadSegment(SegmentName(dir, seg.i+1))
 			testutil.Ok(t, err)
 			defer seg.Close()
-			r = NewLiveReader(logger, seg)
+			r = NewLiveReader(logger, nil, seg)
 
 		case <-readTicker.C:
 			readSegment(r)
@@ -464,7 +464,7 @@ func TestLiveReaderCorrupt_ShortFile(t *testing.T) {
 	testutil.Ok(t, err)
 	defer seg.Close()
 
-	r := NewLiveReader(logger, seg)
+	r := NewLiveReader(logger, nil, seg)
 	testutil.Assert(t, r.Next() == false, "expected no records")
 	testutil.Assert(t, r.Err() == io.EOF, "expected error, got: %v", r.Err())
 }
@@ -512,7 +512,7 @@ func TestLiveReaderCorrupt_RecordTooLongAndShort(t *testing.T) {
 	testutil.Ok(t, err)
 	defer seg.Close()
 
-	r := NewLiveReader(logger, seg)
+	r := NewLiveReader(logger, nil, seg)
 	testutil.Assert(t, r.Next() == false, "expected no records")
 	testutil.Assert(t, r.Err().Error() == "record length greater than a single page: 65542 > 32768", "expected error, got: %v", r.Err())
 }