Merge pull request #1555 from prometheus/beorn7/cd

Checkpoint fingerprint mappings only upon shutdown

storage/local/mapper.go

@@ -72,13 +72,20 @@ func newFPMapper(fpToSeries *seriesMap, p *persistence) (*fpMapper, error) {
 	return m, nil
 }
 
+// checkpoint persists the current mappings.  The caller has to ensure that the
+// provided mappings are not changed concurrently. This method is only called
+// upon shutdown, when no samples are ingested anymore.
+func (m *fpMapper) checkpoint() error {
+	return m.p.checkpointFPMappings(m.mappings)
+}
+
 // mapFP takes a raw fingerprint (as returned by Metrics.FastFingerprint) and
 // returns a truly unique fingerprint. The caller must have locked the raw
 // fingerprint.
 //
 // If an error is encountered, it is returned together with the unchanged raw
 // fingerprint.
-func (m *fpMapper) mapFP(fp model.Fingerprint, metric model.Metric) (model.Fingerprint, error) {
+func (m *fpMapper) mapFP(fp model.Fingerprint, metric model.Metric) model.Fingerprint {
 	// First check if we are in the reserved FP space, in which case this is
 	// automatically a collision that has to be mapped.
 	if fp <= maxMappedFP {
@@ -92,7 +99,7 @@ func (m *fpMapper) mapFP(fp model.Fingerprint, metric model.Metric) (model.Finge
 		// FP exists in memory, but is it for the same metric?
 		if metric.Equal(s.metric) {
 			// Yupp. We are done.
-			return fp, nil
+			return fp
 		}
 		// Collision detected!
 		return m.maybeAddMapping(fp, metric)
@@ -110,28 +117,30 @@ func (m *fpMapper) mapFP(fp model.Fingerprint, metric model.Metric) (model.Finge
 		mappedFP, ok := mappedFPs[ms]
 		if ok {
 			// Historical mapping found, return the mapped FP.
-			return mappedFP, nil
+			return mappedFP
 		}
 	}
 	// If we are here, FP does not exist in memory and is either not mapped
 	// at all, or existing mappings for FP are not for m. Check if we have
 	// something for FP in the archive.
 	archivedMetric, err := m.p.archivedMetric(fp)
-	if err != nil {
-		return fp, err
+	if err != nil || archivedMetric == nil {
+		// Either the archive lookup has returend an error, or fp does
+		// not exist in the archive. In the former case, the storage has
+		// been marked as dirty already. We just carry on for as long as
+		// it goes, assuming that fp does not exist. In either case,
+		// since now we know (or assume) now that fp does not exist,
+		// neither in memory nor in archive, we can safely keep it
+		// unmapped.
+		return fp
 	}
-	if archivedMetric != nil {
-		// FP exists in archive, but is it for the same metric?
-		if metric.Equal(archivedMetric) {
-			// Yupp. We are done.
-			return fp, nil
-		}
-		// Collision detected!
-		return m.maybeAddMapping(fp, metric)
+	// FP exists in archive, but is it for the same metric?
+	if metric.Equal(archivedMetric) {
+		// Yupp. We are done.
+		return fp
 	}
-	// As fp does not exist, neither in memory nor in archive, we can safely
-	// keep it unmapped.
-	return fp, nil
+	// Collision detected!
+	return m.maybeAddMapping(fp, metric)
 }
 
 // maybeAddMapping is only used internally. It takes a detected collision and
@@ -140,7 +149,7 @@ func (m *fpMapper) mapFP(fp model.Fingerprint, metric model.Metric) (model.Finge
 func (m *fpMapper) maybeAddMapping(
 	fp model.Fingerprint,
 	collidingMetric model.Metric,
-) (model.Fingerprint, error) {
+) model.Fingerprint {
 	ms := metricToUniqueString(collidingMetric)
 	m.mtx.RLock()
 	mappedFPs, ok := m.mappings[fp]
@@ -149,20 +158,16 @@ func (m *fpMapper) maybeAddMapping(
 		// fp is locked by the caller, so no further locking required.
 		mappedFP, ok := mappedFPs[ms]
 		if ok {
-			return mappedFP, nil // Existing mapping.
+			return mappedFP // Existing mapping.
 		}
 		// A new mapping has to be created.
 		mappedFP = m.nextMappedFP()
 		mappedFPs[ms] = mappedFP
-		m.mtx.Lock()
-		// Checkpoint mappings after each change.
-		err := m.p.checkpointFPMappings(m.mappings)
-		m.mtx.Unlock()
 		log.Infof(
 			"Collision detected for fingerprint %v, metric %v, mapping to new fingerprint %v.",
 			fp, collidingMetric, mappedFP,
 		)
-		return mappedFP, err
+		return mappedFP
 	}
 	// This is the first collision for fp.
 	mappedFP := m.nextMappedFP()
@@ -170,14 +175,12 @@ func (m *fpMapper) maybeAddMapping(
 	m.mtx.Lock()
 	m.mappings[fp] = mappedFPs
 	m.mappingsCounter.Inc()
-	// Checkpoint mappings after each change.
-	err := m.p.checkpointFPMappings(m.mappings)
 	m.mtx.Unlock()
 	log.Infof(
 		"Collision detected for fingerprint %v, metric %v, mapping to new fingerprint %v.",
 		fp, collidingMetric, mappedFP,
 	)
-	return mappedFP, err
+	return mappedFP
 }
 
 func (m *fpMapper) nextMappedFP() model.Fingerprint {

storage/local/mapper_test.go

@@ -63,22 +63,13 @@ func TestFPMapper(t *testing.T) {
 	defer closer.Close()
 
 	mapper, err := newFPMapper(sm, p)
-	if err != nil {
-		t.Fatal(err)
-	}
 
 	// Everything is empty, resolving a FP should do nothing.
-	gotFP, err := mapper.mapFP(fp1, cm11)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP := mapper.mapFP(fp1, cm11)
 	if wantFP := fp1; gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp1, cm12)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm12)
 	if wantFP := fp1; gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
@@ -86,184 +77,115 @@ func TestFPMapper(t *testing.T) {
 	// cm11 is in sm. Adding cm11 should do nothing. Mapping cm12 should resolve
 	// the collision.
 	sm.put(fp1, &memorySeries{metric: cm11})
-	gotFP, err = mapper.mapFP(fp1, cm11)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm11)
 	if wantFP := fp1; gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp1, cm12)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm12)
 	if wantFP := model.Fingerprint(1); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
 
 	// The mapped cm12 is added to sm, too. That should not change the outcome.
 	sm.put(model.Fingerprint(1), &memorySeries{metric: cm12})
-	gotFP, err = mapper.mapFP(fp1, cm11)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm11)
 	if wantFP := fp1; gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp1, cm12)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm12)
 	if wantFP := model.Fingerprint(1); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
 
 	// Now map cm13, should reproducibly result in the next mapped FP.
-	gotFP, err = mapper.mapFP(fp1, cm13)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm13)
 	if wantFP := model.Fingerprint(2); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp1, cm13)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm13)
 	if wantFP := model.Fingerprint(2); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
 
 	// Add cm13 to sm. Should not change anything.
 	sm.put(model.Fingerprint(2), &memorySeries{metric: cm13})
-	gotFP, err = mapper.mapFP(fp1, cm11)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm11)
 	if wantFP := fp1; gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp1, cm12)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm12)
 	if wantFP := model.Fingerprint(1); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp1, cm13)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm13)
 	if wantFP := model.Fingerprint(2); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
 
 	// Now add cm21 and cm22 in the same way, checking the mapped FPs.
-	gotFP, err = mapper.mapFP(fp2, cm21)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp2, cm21)
 	if wantFP := fp2; gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
 	sm.put(fp2, &memorySeries{metric: cm21})
-	gotFP, err = mapper.mapFP(fp2, cm21)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp2, cm21)
 	if wantFP := fp2; gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp2, cm22)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp2, cm22)
 	if wantFP := model.Fingerprint(3); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
 	sm.put(model.Fingerprint(3), &memorySeries{metric: cm22})
-	gotFP, err = mapper.mapFP(fp2, cm21)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp2, cm21)
 	if wantFP := fp2; gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp2, cm22)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp2, cm22)
 	if wantFP := model.Fingerprint(3); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
 
 	// Map cm31, resulting in a mapping straight away.
-	gotFP, err = mapper.mapFP(fp3, cm31)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp3, cm31)
 	if wantFP := model.Fingerprint(4); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
 	sm.put(model.Fingerprint(4), &memorySeries{metric: cm31})
 
 	// Map cm32, which is now mapped for two reasons...
-	gotFP, err = mapper.mapFP(fp3, cm32)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp3, cm32)
 	if wantFP := model.Fingerprint(5); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
 	sm.put(model.Fingerprint(5), &memorySeries{metric: cm32})
 
 	// Now check ALL the mappings, just to be sure.
-	gotFP, err = mapper.mapFP(fp1, cm11)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm11)
 	if wantFP := fp1; gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp1, cm12)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm12)
 	if wantFP := model.Fingerprint(1); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp1, cm13)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm13)
 	if wantFP := model.Fingerprint(2); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp2, cm21)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp2, cm21)
 	if wantFP := fp2; gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp2, cm22)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp2, cm22)
 	if wantFP := model.Fingerprint(3); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp3, cm31)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp3, cm31)
 	if wantFP := model.Fingerprint(4); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp3, cm32)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp3, cm32)
 	if wantFP := model.Fingerprint(5); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
@@ -273,55 +195,38 @@ func TestFPMapper(t *testing.T) {
 	sm.del(fp1)
 	sm.del(fp2)
 	sm.del(fp3)
-	gotFP, err = mapper.mapFP(fp1, cm11)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm11)
 	if wantFP := fp1; gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp1, cm12)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm12)
 	if wantFP := model.Fingerprint(1); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp1, cm13)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm13)
 	if wantFP := model.Fingerprint(2); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp2, cm21)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp2, cm21)
 	if wantFP := fp2; gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp2, cm22)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp2, cm22)
 	if wantFP := model.Fingerprint(3); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp3, cm31)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp3, cm31)
 	if wantFP := model.Fingerprint(4); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp3, cm32)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp3, cm32)
 	if wantFP := model.Fingerprint(5); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
+	err = mapper.checkpoint()
+	if err != nil {
+		t.Fatal(err)
+	}
 
 	// Load the mapper anew from disk and then check all the mappings again
 	// to make sure all changes have made it to disk.
@@ -329,52 +234,32 @@ func TestFPMapper(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	gotFP, err = mapper.mapFP(fp1, cm11)
-	if err != nil {
-		t.Fatal(err)
-	}
+
+	gotFP = mapper.mapFP(fp1, cm11)
 	if wantFP := fp1; gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp1, cm12)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm12)
 	if wantFP := model.Fingerprint(1); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp1, cm13)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm13)
 	if wantFP := model.Fingerprint(2); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp2, cm21)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp2, cm21)
 	if wantFP := fp2; gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp2, cm22)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp2, cm22)
 	if wantFP := model.Fingerprint(3); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp3, cm31)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp3, cm31)
 	if wantFP := model.Fingerprint(4); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp3, cm32)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp3, cm32)
 	if wantFP := model.Fingerprint(5); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
@@ -386,17 +271,11 @@ func TestFPMapper(t *testing.T) {
 	// the archive).
 	sm.put(fp1, &memorySeries{metric: cm12})
 	p.archiveMetric(fp2, cm22, 0, 0)
-	gotFP, err = mapper.mapFP(fp1, cm12)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp1, cm12)
 	if wantFP := fp1; gotFP != wantFP { // No mapping happened.
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
-	gotFP, err = mapper.mapFP(fp2, cm22)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp2, cm22)
 	if wantFP := model.Fingerprint(3); gotFP != wantFP { // Old mapping still applied.
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}
@@ -405,10 +284,7 @@ func TestFPMapper(t *testing.T) {
 	// archived metric is detected. Again, this is a pathological situation
 	// that must never happen in real operations. It's just staged here to
 	// test the expected behavior.
-	gotFP, err = mapper.mapFP(fp2, cm21)
-	if err != nil {
-		t.Fatal(err)
-	}
+	gotFP = mapper.mapFP(fp2, cm21)
 	if wantFP := model.Fingerprint(6); gotFP != wantFP {
 		t.Errorf("got fingerprint %v, want fingerprint %v", gotFP, wantFP)
 	}

storage/local/persistence.go

@@ -1327,8 +1327,10 @@ loop:
 	close(p.indexingStopped)
 }
 
-// checkpointFPMappings persists the fingerprint mappings. This method is not
-// goroutine-safe.
+// checkpointFPMappings persists the fingerprint mappings. The caller has to
+// ensure that the provided mappings are not changed concurrently. This method
+// is only called upon shutdown or during crash recovery, when no samples are
+// ingested.
 //
 // Description of the file format, v1:
 //

storage/local/storage.go

@@ -356,6 +356,9 @@ func (s *memorySeriesStorage) Stop() error {
 	if err := s.persistence.checkpointSeriesMapAndHeads(s.fpToSeries, s.fpLocker); err != nil {
 		return err
 	}
+	if err := s.mapper.checkpoint(); err != nil {
+		return err
+	}
 
 	if err := s.persistence.close(); err != nil {
 		return err
@@ -587,14 +590,10 @@ func (s *memorySeriesStorage) Append(sample *model.Sample) error {
 	}
 	rawFP := sample.Metric.FastFingerprint()
 	s.fpLocker.Lock(rawFP)
-	fp, err := s.mapper.mapFP(rawFP, sample.Metric)
+	fp := s.mapper.mapFP(rawFP, sample.Metric)
 	defer func() {
 		s.fpLocker.Unlock(fp)
 	}() // Func wrapper because fp might change below.
-	if err != nil {
-		s.persistence.setDirty(fmt.Errorf("error while mapping fingerprint %v: %s", rawFP, err))
-		return err
-	}
 	if fp != rawFP {
 		// Switch locks.
 		s.fpLocker.Unlock(rawFP)

storage/local/storage_test.go

@@ -1683,10 +1683,7 @@ func verifyStorageRandom(t testing.TB, s *memorySeriesStorage, samples model.Sam
 	result := true
 	for _, i := range rand.Perm(len(samples)) {
 		sample := samples[i]
-		fp, err := s.mapper.mapFP(sample.Metric.FastFingerprint(), sample.Metric)
-		if err != nil {
-			t.Fatal(err)
-		}
+		fp := s.mapper.mapFP(sample.Metric.FastFingerprint(), sample.Metric)
 		p := s.NewPreloader()
 		it := p.PreloadInstant(fp, sample.Timestamp, 0)
 		found := it.ValueAtOrBeforeTime(sample.Timestamp)
@@ -1726,10 +1723,7 @@ func verifyStorageSequential(t testing.TB, s *memorySeriesStorage, samples model
 		p.Close()
 	}()
 	for i, sample := range samples {
-		newFP, err := s.mapper.mapFP(sample.Metric.FastFingerprint(), sample.Metric)
-		if err != nil {
-			t.Fatal(err)
-		}
+		newFP := s.mapper.mapFP(sample.Metric.FastFingerprint(), sample.Metric)
 		if it == nil || newFP != fp {
 			fp = newFP
 			p.Close()
@@ -1782,10 +1776,7 @@ func TestAppendOutOfOrder(t *testing.T) {
 		})
 	}
 
-	fp, err := s.mapper.mapFP(m.FastFingerprint(), m)
-	if err != nil {
-		t.Fatal(err)
-	}
+	fp := s.mapper.mapFP(m.FastFingerprint(), m)
 
 	pl := s.NewPreloader()
 	defer pl.Close()