[#1685] metabase: Cache expired bucket

```
goos: linux
goarch: amd64
pkg: git.frostfs.info/TrueCloudLab/frostfs-node/pkg/local_object_storage/metabase
cpu: 11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz
                          │    master    │               expired                │
                          │    sec/op    │    sec/op     vs base                │
Select/string_equal-8       4.007m ± 10%   3.529m ± 11%  -11.94% (p=0.000 n=10)
Select/string_not_equal-8   3.834m ± 12%   3.440m ±  7%  -10.29% (p=0.029 n=10)
Select/common_prefix-8      3.470m ±  9%   3.240m ±  6%        ~ (p=0.105 n=10)
Select/unknown-8            3.156m ±  3%   3.198m ±  6%        ~ (p=0.631 n=10)
geomean                     3.602m         3.349m         -7.03%

                          │    master    │               expired               │
                          │     B/op     │     B/op      vs base               │
Select/string_equal-8       1.907Mi ± 0%   1.885Mi ± 0%  -1.18% (p=0.000 n=10)
Select/string_not_equal-8   1.907Mi ± 0%   1.885Mi ± 0%  -1.18% (p=0.000 n=10)
Select/common_prefix-8      1.907Mi ± 0%   1.885Mi ± 0%  -1.18% (p=0.000 n=10)
Select/unknown-8            1.900Mi ± 0%   1.877Mi ± 0%  -1.18% (p=0.000 n=10)
geomean                     1.905Mi        1.883Mi       -1.18%

                          │   master    │              expired               │
                          │  allocs/op  │  allocs/op   vs base               │
Select/string_equal-8       47.03k ± 0%   46.04k ± 0%  -2.12% (p=0.000 n=10)
Select/string_not_equal-8   47.03k ± 0%   46.04k ± 0%  -2.12% (p=0.000 n=10)
Select/common_prefix-8      47.03k ± 0%   46.04k ± 0%  -2.12% (p=0.000 n=10)
Select/unknown-8            46.04k ± 0%   45.05k ± 0%  -2.16% (p=0.000 n=10)
geomean                     46.78k        45.79k       -2.13%
```

Change-Id: I9c7a5e1f5c8b9eb3f25a563fd74c6ad2a9d1b92e
Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

pkg/local_object_storage/metabase/bucket_cache.go

@@ -1,6 +1,7 @@
 package meta
 
 import (
+	cid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/container/id"
 	"go.etcd.io/bbolt"
 )
 
@@ -8,10 +9,11 @@ type bucketCache struct {
 	locked    *bbolt.Bucket
 	graveyard *bbolt.Bucket
 	garbage   *bbolt.Bucket
+	expired   map[cid.ID]*bbolt.Bucket
 }
 
 func newBucketCache() *bucketCache {
-	return &bucketCache{}
+	return &bucketCache{expired: make(map[cid.ID]*bbolt.Bucket)}
 }
 
 func getLockedBucket(bc *bucketCache, tx *bbolt.Tx) *bbolt.Bucket {
@@ -43,3 +45,24 @@ func getBucket(cache **bbolt.Bucket, tx *bbolt.Tx, name []byte) *bbolt.Bucket {
 	*cache = tx.Bucket(name)
 	return *cache
 }
+
+func getExpiredBucket(bc *bucketCache, tx *bbolt.Tx, cnr cid.ID) *bbolt.Bucket {
+	if bc == nil {
+		bucketName := make([]byte, bucketKeySize)
+		bucketName = objectToExpirationEpochBucketName(cnr, bucketName)
+		return tx.Bucket(bucketName)
+	}
+	return getMappedBucket(bc.expired, tx, objectToExpirationEpochBucketName, cnr)
+}
+
+func getMappedBucket(m map[cid.ID]*bbolt.Bucket, tx *bbolt.Tx, nameFunc func(cid.ID, []byte) []byte, cnr cid.ID) *bbolt.Bucket {
+	value, ok := m[cnr]
+	if ok {
+		return value
+	}
+
+	bucketName := make([]byte, bucketKeySize)
+	bucketName = nameFunc(cnr, bucketName)
+	m[cnr] = getBucket(&value, tx, bucketName)
+	return value
+}

pkg/local_object_storage/metabase/exists.go

@@ -162,7 +162,7 @@ func objectStatusWithCache(bc *bucketCache, tx *bbolt.Tx, addr oid.Address, curr
 		return 0, nil
 	}
 
-	expired, err := isExpired(tx, addr, currEpoch)
+	expired, err := isExpiredWithCache(bc, tx, addr, currEpoch)
 	if err != nil {
 		return 0, err
 	}

pkg/local_object_storage/metabase/expired.go

@@ -74,9 +74,11 @@ func (db *DB) FilterExpired(ctx context.Context, epoch uint64, addresses []oid.A
 }
 
 func isExpired(tx *bbolt.Tx, addr oid.Address, currEpoch uint64) (bool, error) {
-	bucketName := make([]byte, bucketKeySize)
-	bucketName = objectToExpirationEpochBucketName(addr.Container(), bucketName)
-	b := tx.Bucket(bucketName)
+	return isExpiredWithCache(nil, tx, addr, currEpoch)
+}
+
+func isExpiredWithCache(bc *bucketCache, tx *bbolt.Tx, addr oid.Address, currEpoch uint64) (bool, error) {
+	b := getExpiredBucket(bc, tx, addr.Container())
 	if b == nil {
 		return false, nil
 	}