Fix review comments

Signed-off-by: Ganesh Vernekar <cs15btech11018@iith.ac.in>

checkpoint.go

@@ -23,10 +23,7 @@ import (
 	"strconv"
 	"strings"
 
-	"github.com/go-kit/kit/log"
-	"github.com/go-kit/kit/log/level"
 	"github.com/pkg/errors"
-	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/tsdb/fileutil"
 	"github.com/prometheus/tsdb/wal"
 )
@@ -101,12 +98,7 @@ const checkpointPrefix = "checkpoint."
 // segmented format as the original WAL itself.
 // This makes it easy to read it through the WAL package and concatenate
 // it with the original WAL.
-//
+func Checkpoint(w *wal.WAL, m, n int, keep func(id uint64) bool, mint int64) (*CheckpointStats, error) {
-// Non-critical errors are logged and not returned.
-func Checkpoint(logger log.Logger, w *wal.WAL, m, n int, keep func(id uint64) bool, mint int64, checkpointDeleteFail prometheus.Counter) (*CheckpointStats, error) {
-	if logger == nil {
-		logger = log.NewNopLogger()
-	}
 	stats := &CheckpointStats{}
 
 	var sr io.Reader
@@ -273,18 +265,5 @@ func Checkpoint(logger log.Logger, w *wal.WAL, m, n int, keep func(id uint64) bo
 	if err := closeAll(closers...); err != nil {
 		return stats, errors.Wrap(err, "close opened files")
 	}
-	if err := w.Truncate(n + 1); err != nil {
-		// If truncating fails, we'll just try again at the next checkpoint.
-		// Leftover segments will just be ignored in the future if there's a checkpoint
-		// that supersedes them.
-		level.Error(logger).Log("msg", "truncating segments failed", "err", err)
-	}
-	if err := DeleteCheckpoints(w.Dir(), n); err != nil {
-		// Leftover old checkpoints do not cause problems down the line beyond
-		// occupying disk space.
-		// They will just be ignored since a higher checkpoint exists.
-		level.Error(logger).Log("msg", "delete old checkpoints", "err", err)
-		checkpointDeleteFail.Add(float64(1))
-	}
 	return stats, nil
 }

checkpoint_test.go

@@ -20,7 +20,6 @@ import (
 	"path/filepath"
 	"testing"
 
-	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/tsdb/fileutil"
 	"github.com/prometheus/tsdb/labels"
 	"github.com/prometheus/tsdb/testutil"
@@ -138,10 +137,12 @@ func TestCheckpoint(t *testing.T) {
 	}
 	testutil.Ok(t, w.Close())
 
-	_, err = Checkpoint(nil, w, 100, 106, func(x uint64) bool {
+	_, err = Checkpoint(w, 100, 106, func(x uint64) bool {
 		return x%2 == 0
-	}, last/2, prometheus.NewCounter(prometheus.CounterOpts{}))
+	}, last/2)
 	testutil.Ok(t, err)
+	testutil.Ok(t, w.Truncate(107))
+	testutil.Ok(t, DeleteCheckpoints(w.Dir(), 106))
 
 	// Only the new checkpoint should be left.
 	files, err := fileutil.ReadDir(dir)

head.go

@@ -89,7 +89,12 @@ type headMetrics struct {
 	maxTime                 prometheus.GaugeFunc
 	samplesAppended         prometheus.Counter
 	walTruncateDuration     prometheus.Summary
+	headTruncateFail        prometheus.Counter
+	headTruncateTotal       prometheus.Counter
 	checkpointDeleteFail    prometheus.Counter
+	checkpointDeleteTotal   prometheus.Counter
+	checkpointCreationFail  prometheus.Counter
+	checkpointCreationTotal prometheus.Counter
 }
 
 func newHeadMetrics(h *Head, r prometheus.Registerer) *headMetrics {
@@ -151,9 +156,29 @@ func newHeadMetrics(h *Head, r prometheus.Registerer) *headMetrics {
 		Name: "prometheus_tsdb_head_samples_appended_total",
 		Help: "Total number of appended samples.",
 	})
+	m.headTruncateFail = prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "prometheus_tsdb_head_truncations_failed_total",
+		Help: "Total number of head truncations that failed.",
+	})
+	m.headTruncateTotal = prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "prometheus_tsdb_head_truncations_total",
+		Help: "Total number of head truncations attempted.",
+	})
 	m.checkpointDeleteFail = prometheus.NewCounter(prometheus.CounterOpts{
-		Name: "prometheus_tsdb_checkpoint_delete_fail",
+		Name: "prometheus_tsdb_checkpoint_deletions_failed_total",
-		Help: "Number of times deletion of old checkpoint failed.",
+		Help: "Total number of checkpoint deletions that failed.",
+	})
+	m.checkpointDeleteTotal = prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "prometheus_tsdb_checkpoint_deletions_total",
+		Help: "Total number of checkpoint deletions attempted.",
+	})
+	m.checkpointCreationFail = prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "prometheus_tsdb_checkpoint_creations_failed_total",
+		Help: "Total number of checkpoint creations that failed.",
+	})
+	m.checkpointCreationTotal = prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "prometheus_tsdb_checkpoint_creations_total",
+		Help: "Total number of checkpoint creations attempted.",
 	})
 
 	if r != nil {
@@ -171,7 +196,12 @@ func newHeadMetrics(h *Head, r prometheus.Registerer) *headMetrics {
 			m.gcDuration,
 			m.walTruncateDuration,
 			m.samplesAppended,
+			m.headTruncateFail,
+			m.headTruncateTotal,
 			m.checkpointDeleteFail,
+			m.checkpointDeleteTotal,
+			m.checkpointCreationFail,
+			m.checkpointCreationTotal,
 		)
 	}
 	return m
@@ -427,7 +457,12 @@ func (h *Head) Init() error {
 }
 
 // Truncate removes old data before mint from the head.
-func (h *Head) Truncate(mint int64) error {
+func (h *Head) Truncate(mint int64) (err error) {
+	defer func() {
+		if err != nil {
+			h.metrics.headTruncateFail.Inc()
+		}
+	}()
 	initialize := h.MinTime() == math.MaxInt64
 
 	if h.MinTime() >= mint && !initialize {
@@ -446,6 +481,7 @@ func (h *Head) Truncate(mint int64) error {
 		return nil
 	}
 
+	h.metrics.headTruncateTotal.Inc()
 	start := time.Now()
 
 	h.gc()
@@ -475,9 +511,25 @@ func (h *Head) Truncate(mint int64) error {
 	keep := func(id uint64) bool {
 		return h.series.getByID(id) != nil
 	}
-	if _, err = Checkpoint(h.logger, h.wal, m, n, keep, mint, h.metrics.checkpointDeleteFail); err != nil {
+	h.metrics.checkpointCreationTotal.Inc()
+	if _, err = Checkpoint(h.wal, m, n, keep, mint); err != nil {
+		h.metrics.checkpointCreationFail.Inc()
 		return errors.Wrap(err, "create checkpoint")
 	}
+	if err := h.wal.Truncate(n + 1); err != nil {
+		// If truncating fails, we'll just try again at the next checkpoint.
+		// Leftover segments will just be ignored in the future if there's a checkpoint
+		// that supersedes them.
+		level.Error(h.logger).Log("msg", "truncating segments failed", "err", err)
+	}
+	h.metrics.checkpointDeleteTotal.Inc()
+	if err := DeleteCheckpoints(h.wal.Dir(), n); err != nil {
+		// Leftover old checkpoints do not cause problems down the line beyond
+		// occupying disk space.
+		// They will just be ignored since a higher checkpoint exists.
+		level.Error(h.logger).Log("msg", "delete old checkpoints", "err", err)
+		h.metrics.checkpointDeleteFail.Inc()
+	}
 	h.metrics.walTruncateDuration.Observe(time.Since(start).Seconds())
 
 	level.Info(h.logger).Log("msg", "WAL checkpoint complete",

wal/wal.go

@@ -163,6 +163,7 @@ type WAL struct {
 	pageFlushes     prometheus.Counter
 	pageCompletions prometheus.Counter
 	truncateFail    prometheus.Counter
+	truncateTotal   prometheus.Counter
 }
 
 // New returns a new WAL over the given directory.
@@ -203,11 +204,15 @@ func NewSize(logger log.Logger, reg prometheus.Registerer, dir string, segmentSi
 		Help: "Total number of completed pages.",
 	})
 	w.truncateFail = prometheus.NewCounter(prometheus.CounterOpts{
-		Name: "prometheus_tsdb_wal_truncate_fail",
+		Name: "prometheus_tsdb_wal_truncations_failed_total",
-		Help: "Number of times WAL truncation failed.",
+		Help: "Total number of WAL truncations that failed.",
+	})
+	w.truncateTotal = prometheus.NewCounter(prometheus.CounterOpts{
+		Name: "prometheus_tsdb_wal_truncations_total",
+		Help: "Total number of WAL truncations attempted.",
 	})
 	if reg != nil {
-		reg.MustRegister(w.fsyncDuration, w.pageFlushes, w.pageCompletions, w.truncateFail)
+		reg.MustRegister(w.fsyncDuration, w.pageFlushes, w.pageCompletions, w.truncateFail, w.truncateTotal)
 	}
 
 	_, j, err := w.Segments()
@@ -532,18 +537,22 @@ func (w *WAL) Segments() (m, n int, err error) {
 }
 
 // Truncate drops all segments before i.
-func (w *WAL) Truncate(i int) error {
+func (w *WAL) Truncate(i int) (err error) {
+	w.truncateTotal.Inc()
+	defer func() {
+		if err != nil {
+			w.truncateFail.Inc()
+		}
+	}()
 	refs, err := listSegments(w.dir)
 	if err != nil {
-		w.truncateFail.Add(float64(1))
 		return err
 	}
 	for _, r := range refs {
 		if r.n >= i {
 			break
 		}
-		if err := os.Remove(filepath.Join(w.dir, r.s)); err != nil {
+		if err = os.Remove(filepath.Join(w.dir, r.s)); err != nil {
-			w.truncateFail.Add(float64(1))
 			return err
 		}
 	}