Compact TSDB on open.

CHANGELOG.md

@@ -13,6 +13,7 @@
 * [CHANGE] Ingester: Chunks flushed via /flush stay in memory until retention period is reached. This affects `cortex_ingester_memory_chunks` metric. #2778
 * [CHANGE] Querier: the error message returned when the query time range exceeds `-store.max-query-length` has changed from `invalid query, length > limit (X > Y)` to `the query time range exceeds the limit (query length: X, limit: Y)`. #2826
 * [CHANGE] KV: The `role` label which was a label of `multi` KV store client only has been added to metrics of every KV store client. If KV store client is not `multi`, then the value of `role` label is `primary`. #2837
+* [CHANGE] Experimental TSDB: compact head when opening TSDB. This should only affect ingester startup after it was unable to compact head in previous run. #2870
 * [FEATURE] Introduced `ruler.for-outage-tolerance`, Max time to tolerate outage for restoring "for" state of alert. #2783
 * [FEATURE] Introduced `ruler.for-grace-period`, Minimum duration between alert and restored "for" state. This is maintained only for alerts with configured "for" time greater than grace period. #2783
 * [FEATURE] Introduced `ruler.resend-delay`, Minimum amount of time to wait before resending an alert to Alertmanager. #2783

pkg/ingester/ingester_v2.go

@@ -895,6 +895,14 @@ func (i *Ingester) createTSDB(userID string) (*userTSDB, error) {
 	}
 	db.DisableCompactions() // we will compact on our own schedule
 
+	// Run compaction before using this TSDB. If there is data in head that needs to be put into blocks,
+	// this will actually create the blocks. If there is no data (empty TSDB), this is a no-op.
+	// We don't do blocks compaction.
+	err = db.Compact()
+	if err != nil {
+		return nil, err
+	}
+
 	userDB.DB = db
 	// We set the limiter here because we don't want to limit
 	// series during WAL replay.

pkg/ingester/ingester_v2_test.go

@@ -22,6 +22,7 @@ import (
 	"github.com/prometheus/common/model"
 	"github.com/prometheus/prometheus/pkg/labels"
 	"github.com/prometheus/prometheus/storage"
+	"github.com/prometheus/prometheus/tsdb"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/mock"
 	"github.com/stretchr/testify/require"
@@ -1602,3 +1603,76 @@ func pushSingleSample(t *testing.T, i *Ingester) {
 	_, err := i.v2Push(ctx, req)
 	require.NoError(t, err)
 }
+
+func TestHeadCompactionOnStartup(t *testing.T) {
+	// Create a temporary directory for TSDB
+	tempDir, err := ioutil.TempDir("", "tsdb")
+	require.NoError(t, err)
+	t.Cleanup(func() {
+		os.RemoveAll(tempDir)
+	})
+
+	// Build TSDB for user, with data covering 24 hours.
+	{
+		// Number of full chunks, 12 chunks for 24hrs.
+		numFullChunks := 12
+		chunkRange := 2 * time.Hour.Milliseconds()
+
+		userDir := filepath.Join(tempDir, userID)
+		require.NoError(t, os.Mkdir(userDir, 0700))
+
+		db, err := tsdb.Open(userDir, nil, nil, &tsdb.Options{
+			RetentionDuration: int64(time.Hour * 25 / time.Millisecond),
+			NoLockfile:        true,
+			MinBlockDuration:  chunkRange,
+			MaxBlockDuration:  chunkRange,
+		})
+		require.NoError(t, err)
+
+		db.DisableCompactions()
+		head := db.Head()
+
+		l := labels.Labels{{Name: "n", Value: "v"}}
+		for i := 0; i < numFullChunks; i++ {
+			// Not using db.Appender() as it checks for compaction.
+			app := head.Appender()
+			_, err := app.Add(l, int64(i)*chunkRange+1, 9.99)
+			require.NoError(t, err)
+			_, err = app.Add(l, int64(i+1)*chunkRange, 9.99)
+			require.NoError(t, err)
+			require.NoError(t, app.Commit())
+		}
+
+		dur := time.Duration(head.MaxTime()-head.MinTime()) * time.Millisecond
+		require.True(t, dur > 23*time.Hour)
+		require.Empty(t, db.Blocks())
+		require.NoError(t, db.Close())
+	}
+
+	clientCfg := defaultClientTestConfig()
+	limits := defaultLimitsTestConfig()
+
+	overrides, err := validation.NewOverrides(limits, nil)
+	require.NoError(t, err)
+
+	ingesterCfg := defaultIngesterTestConfig()
+	ingesterCfg.TSDBEnabled = true
+	ingesterCfg.TSDBConfig.Dir = tempDir
+	ingesterCfg.TSDBConfig.Backend = "s3"
+	ingesterCfg.TSDBConfig.S3.Endpoint = "localhost"
+
+	ingester, err := NewV2(ingesterCfg, clientCfg, overrides, nil)
+	require.NoError(t, err)
+	require.NoError(t, services.StartAndAwaitRunning(context.Background(), ingester))
+
+	defer services.StopAndAwaitTerminated(context.Background(), ingester) //nolint:errcheck
+
+	db := ingester.getTSDB(userID)
+	require.NotNil(t, db)
+
+	h := db.Head()
+
+	dur := time.Duration(h.MaxTime()-h.MinTime()) * time.Millisecond
+	require.True(t, dur < 4*time.Hour)
+	require.NotEmpty(t, db.Blocks())
+}