[#1298] writecache: Add shrink flag for Seal command

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

cmd/frostfs-cli/modules/control/writecache.go

@@ -9,7 +9,10 @@ import (
 	"github.com/spf13/cobra"
 )
 
-const restoreModeFlag = "restore-mode"
+const (
+	restoreModeFlag = "restore-mode"
+	shrinkFlag      = "shrink"
+)
 
 var writecacheShardCmd = &cobra.Command{
 	Use:   "writecache",
@@ -29,11 +32,13 @@ func sealWritecache(cmd *cobra.Command, _ []string) {
 
 	ignoreErrors, _ := cmd.Flags().GetBool(ignoreErrorsFlag)
 	restoreMode, _ := cmd.Flags().GetBool(restoreModeFlag)
+	shrink, _ := cmd.Flags().GetBool(shrinkFlag)
 
 	req := &control.SealWriteCacheRequest{Body: &control.SealWriteCacheRequest_Body{
 		Shard_ID:     getShardIDList(cmd),
 		IgnoreErrors: ignoreErrors,
 		RestoreMode:  restoreMode,
+		Shrink:       shrink,
 	}}
 
 	signRequest(cmd, pk, req)
@@ -73,6 +78,7 @@ func initControlShardsWritecacheCmd() {
 	ff.Bool(shardAllFlag, false, "Process all shards")
 	ff.Bool(ignoreErrorsFlag, true, "Skip invalid/unreadable objects")
 	ff.Bool(restoreModeFlag, false, "Restore writecache's mode after sealing")
+	ff.Bool(shrinkFlag, false, "Shrink writecache's internal storage")
 
 	sealWritecacheShardCmd.MarkFlagsMutuallyExclusive(shardIDFlag, shardAllFlag)
 }

internal/logs/logs.go

@@ -539,4 +539,5 @@ const (
 	PolicerCouldNotGetChunk                                              = "could not get EC chunk"
 	PolicerCouldNotGetChunks                                             = "could not get EC chunks"
 	AuditEventLogRecord                                                  = "audit event log record"
+	WritecacheShrinkSkippedNotEmpty                                      = "writecache shrink skipped: database is not empty"
 )

pkg/local_object_storage/engine/writecache.go

@@ -71,6 +71,7 @@ type SealWriteCachePrm struct {
 	ShardIDs     []*shard.ID
 	IgnoreErrors bool
 	RestoreMode  bool
+	Shrink       bool
 }
 
 type ShardSealResult struct {
@@ -116,7 +117,7 @@ func (e *StorageEngine) SealWriteCache(ctx context.Context, prm SealWriteCachePr
 				return nil
 			}
 
-			err := sh.SealWriteCache(egCtx, shard.SealWriteCachePrm{IgnoreErrors: prm.IgnoreErrors, RestoreMode: prm.RestoreMode})
+			err := sh.SealWriteCache(egCtx, shard.SealWriteCachePrm{IgnoreErrors: prm.IgnoreErrors, RestoreMode: prm.RestoreMode, Shrink: prm.Shrink})
 
 			resGuard.Lock()
 			defer resGuard.Unlock()

pkg/local_object_storage/shard/writecache.go

@@ -61,6 +61,7 @@ func (s *Shard) FlushWriteCache(ctx context.Context, p FlushWriteCachePrm) error
 type SealWriteCachePrm struct {
 	IgnoreErrors bool
 	RestoreMode  bool
+	Shrink       bool
 }
 
 // SealWriteCache flushes all data from the write-cache and moves it to degraded read only mode.
@@ -87,5 +88,5 @@ func (s *Shard) SealWriteCache(ctx context.Context, p SealWriteCachePrm) error {
 		return ErrDegradedMode
 	}
 
-	return s.writeCache.Seal(ctx, writecache.SealPrm{IgnoreErrors: p.IgnoreErrors, RestoreMode: p.RestoreMode})
+	return s.writeCache.Seal(ctx, writecache.SealPrm{IgnoreErrors: p.IgnoreErrors, RestoreMode: p.RestoreMode, Shrink: p.Shrink})
 }

pkg/local_object_storage/writecache/flush.go

@@ -291,7 +291,7 @@ func (c *cache) Flush(ctx context.Context, ignoreErrors, seal bool) error {
 
 	if seal {
 		m := c.mode | mode.ReadOnly
-		if err := c.setMode(ctx, m, ignoreErrors); err != nil {
+		if err := c.setMode(ctx, m, setModePrm{ignoreErrors: ignoreErrors}); err != nil {
 			return err
 		}
 		c.metrics.SetMode(mode.ConvertToComponentModeDegraded(m))

pkg/local_object_storage/writecache/mode.go

@@ -2,16 +2,25 @@ package writecache
 
 import (
 	"context"
+	"errors"
 	"fmt"
+	"os"
+	"path/filepath"
 	"time"
 
 	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
 	"git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/shard/mode"
 	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
+	"go.etcd.io/bbolt"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/trace"
 )
 
+type setModePrm struct {
+	ignoreErrors bool
+	shrink       bool
+}
+
 // SetMode sets write-cache mode of operation.
 // When shard is put in read-only mode all objects in memory are flushed to disk
 // and all background jobs are suspended.
@@ -25,7 +34,7 @@ func (c *cache) SetMode(m mode.Mode) error {
 	c.modeMtx.Lock()
 	defer c.modeMtx.Unlock()
 
-	err := c.setMode(ctx, m, true)
+	err := c.setMode(ctx, m, setModePrm{ignoreErrors: true})
 	if err == nil {
 		c.metrics.SetMode(mode.ConvertToComponentModeDegraded(m))
 	}
@@ -33,21 +42,19 @@ func (c *cache) SetMode(m mode.Mode) error {
 }
 
 // setMode applies new mode. Must be called with cache.modeMtx lock taken.
-func (c *cache) setMode(ctx context.Context, m mode.Mode, ignoreErrors bool) error {
+func (c *cache) setMode(ctx context.Context, m mode.Mode, prm setModePrm) error {
 	var err error
 	turnOffMeta := m.NoMetabase()
 
 	if turnOffMeta && !c.mode.NoMetabase() {
-		err = c.flush(ctx, ignoreErrors)
+		err = c.flush(ctx, prm.ignoreErrors)
 		if err != nil {
 			return err
 		}
 	}
 
-	if c.db != nil {
-		if err = c.db.Close(); err != nil {
-			return fmt.Errorf("can't close write-cache database: %w", err)
-		}
+	if err := c.closeDB(prm.shrink); err != nil {
+		return err
 	}
 
 	// Suspend producers to ensure there are channel send operations in fly.
@@ -71,6 +78,40 @@ func (c *cache) setMode(ctx context.Context, m mode.Mode, ignoreErrors bool) err
 	return nil
 }
 
+func (c *cache) closeDB(shrink bool) error {
+	if c.db == nil {
+		return nil
+	}
+	if !shrink {
+		if err := c.db.Close(); err != nil {
+			return fmt.Errorf("can't close write-cache database: %w", err)
+		}
+		return nil
+	}
+
+	var empty bool
+	err := c.db.View(func(tx *bbolt.Tx) error {
+		b := tx.Bucket(defaultBucket)
+		empty = b == nil || b.Stats().KeyN == 0
+		return nil
+	})
+	if err != nil && !errors.Is(err, bbolt.ErrDatabaseNotOpen) {
+		return fmt.Errorf("failed to check DB items: %w", err)
+	}
+	if err := c.db.Close(); err != nil {
+		return fmt.Errorf("can't close write-cache database: %w", err)
+	}
+	if empty {
+		err := os.Remove(filepath.Join(c.path, dbName))
+		if err != nil && !os.IsNotExist(err) {
+			return fmt.Errorf("failed to remove DB file: %w", err)
+		}
+	} else {
+		c.log.Info(logs.WritecacheShrinkSkippedNotEmpty)
+	}
+	return nil
+}
+
 // readOnly returns true if current mode is read-only.
 // `c.modeMtx` must be taken.
 func (c *cache) readOnly() bool {

pkg/local_object_storage/writecache/seal.go

@@ -22,13 +22,13 @@ func (c *cache) Seal(ctx context.Context, prm SealPrm) error {
 
 	sourceMode := c.mode
 	// flush will be done by setMode
-	err := c.setMode(ctx, mode.DegradedReadOnly, prm.IgnoreErrors)
+	err := c.setMode(ctx, mode.DegradedReadOnly, setModePrm{ignoreErrors: prm.IgnoreErrors, shrink: prm.Shrink})
 	if err != nil {
 		return err
 	}
 	c.metrics.SetMode(mode.ComponentDisabled)
 	if prm.RestoreMode {
-		err = c.setMode(ctx, sourceMode, prm.IgnoreErrors)
+		err = c.setMode(ctx, sourceMode, setModePrm{ignoreErrors: prm.IgnoreErrors})
 		if err == nil {
 			c.metrics.SetMode(mode.ConvertToComponentMode(sourceMode))
 		}

pkg/local_object_storage/writecache/writecache.go

@@ -23,6 +23,7 @@ type Info struct {
 type SealPrm struct {
 	IgnoreErrors bool
 	RestoreMode  bool
+	Shrink       bool
 }
 
 // Cache represents write-cache for objects.

pkg/services/control/server/seal_writecache.go

@@ -20,6 +20,7 @@ func (s *Server) SealWriteCache(ctx context.Context, req *control.SealWriteCache
 		ShardIDs:     s.getShardIDList(req.GetBody().GetShard_ID()),
 		IgnoreErrors: req.GetBody().GetIgnoreErrors(),
 		RestoreMode:  req.GetBody().GetRestoreMode(),
+		Shrink:       req.GetBody().GetShrink(),
 	}
 
 	res, err := s.s.SealWriteCache(ctx, prm)

pkg/services/control/service.proto

@@ -658,6 +658,9 @@ message SealWriteCacheRequest {
 
     // If true, then writecache will be sealed, but mode will be restored to the current one.
     bool restore_mode = 4;
+
+    // If true, then writecache will shrink internal storage.
+    bool shrink = 5;
   }
 
   Body body = 1;