[#917] engine: Allow to detach shards

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

pkg/local_object_storage/engine/shards.go

@@ -2,7 +2,9 @@ package engine
 
 import (
 	"context"
+	"errors"
 	"fmt"
+	"sync"
 	"sync/atomic"
 
 	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/logs"
@@ -14,6 +16,7 @@ import (
 	"github.com/google/uuid"
 	"github.com/panjf2000/ants/v2"
 	"go.uber.org/zap"
+	"golang.org/x/sync/errgroup"
 )
 
 var errShardNotFound = logicerr.New("shard not found")
@@ -344,6 +347,100 @@ func (e *StorageEngine) HandleNewEpoch(ctx context.Context, epoch uint64) {
 	}
 }
 
+func (e *StorageEngine) DetachShards(ids []*shard.ID) error {
+	if len(ids) == 0 {
+		return logicerr.New("ids must be non-empty")
+	}
+
+	deletedShards, err := e.deleteShards(ids)
+	if err != nil {
+		return err
+	}
+
+	return e.closeShards(deletedShards)
+}
+
+// closeShards closes deleted shards. Tries to close all shards.
+// Returns single error with joined shard errors.
+func (e *StorageEngine) closeShards(deletedShards []hashedShard) error {
+	var multiErr error
+	var multiErrGuard sync.Mutex
+	var eg errgroup.Group
+	for _, sh := range deletedShards {
+		sh := sh
+		eg.Go(func() error {
+			err := sh.SetMode(mode.Disabled)
+			if err != nil {
+				e.log.Error(logs.EngineCouldNotChangeShardModeToDisabled,
+					zap.Stringer("id", sh.ID()),
+					zap.Error(err),
+				)
+				multiErrGuard.Lock()
+				multiErr = errors.Join(multiErr, fmt.Errorf("could not change shard (id:%s) mode to disabled: %w", sh.ID(), err))
+				multiErrGuard.Unlock()
+			}
+
+			err = sh.Close()
+			if err != nil {
+				e.log.Error(logs.EngineCouldNotCloseRemovedShard,
+					zap.Stringer("id", sh.ID()),
+					zap.Error(err),
+				)
+				multiErrGuard.Lock()
+				multiErr = errors.Join(multiErr, fmt.Errorf("could not close removed shard (id:%s): %w", sh.ID(), err))
+				multiErrGuard.Unlock()
+			}
+			return nil
+		})
+	}
+	if err := eg.Wait(); err != nil {
+		return err
+	}
+	return multiErr
+}
+
+// deleteShards deletes shards with specified ids from engine shard list
+// and releases all engine resources associated with shards.
+// Returns deleted shards or error if some shard could not be deleted.
+func (e *StorageEngine) deleteShards(ids []*shard.ID) ([]hashedShard, error) {
+	ss := make([]hashedShard, 0, len(ids))
+
+	e.mtx.Lock()
+	defer e.mtx.Unlock()
+
+	for _, id := range ids {
+		idStr := id.String()
+		sh, found := e.shards[idStr]
+		if !found {
+			return nil, errShardNotFound
+		}
+		ss = append(ss, sh)
+	}
+
+	if len(ss) == len(e.shards) {
+		return nil, logicerr.New("could not delete all the shards")
+	}
+
+	for _, sh := range ss {
+		idStr := sh.ID().String()
+
+		sh.DeleteShardMetrics()
+
+		delete(e.shards, idStr)
+
+		pool, ok := e.shardPools[idStr]
+		if ok {
+			pool.Release()
+			delete(e.shardPools, idStr)
+		}
+
+		e.log.Info(logs.EngineShardHasBeenRemoved,
+			zap.String("id", idStr))
+	}
+
+	return ss, nil
+}
+
 func (s hashedShard) Hash() uint64 {
 	return s.hash
 }