services: add default values for NeoFSBlockFetcher configuration

The minimum sufficient configuration is Addresses and ContainerID,
example:
```
  NeoFSBlockFetcher:
    Enabled: true
    Addresses:
      - st1.storage.fs.neo.org:8080
      - st2.storage.fs.neo.org:8080
      - st3.storage.fs.neo.org:8080
      - st4.storage.fs.neo.org:8080
    ContainerID: "87JRc7vyWcjW8uS32LMoLTAj4ckCzFZWfKbacjU3sAob"
```

Close #3718

Signed-off-by: Ekaterina Pavlova <ekt@morphbits.io>

pkg/config/application_config_test.go

@@ -194,32 +194,6 @@ func TestNeoFSBlockFetcherValidation(t *testing.T) {
 			shouldFail: true,
 			errMsg:     "addresses are not set",
 		},
-		{
-			cfg: NeoFSBlockFetcher{
-				InternalService: InternalService{Enabled: true},
-				Timeout:         time.Second,
-				ContainerID:     validContainerID,
-				Addresses:       []string{"127.0.0.1"},
-				OIDBatchSize:    10,
-				BQueueSize:      5,
-			},
-			shouldFail: true,
-			errMsg:     "BQueueSize (5) is lower than OIDBatchSize (10)",
-		},
-		{
-			cfg: NeoFSBlockFetcher{
-				InternalService:      InternalService{Enabled: true},
-				Timeout:              time.Second,
-				ContainerID:          validContainerID,
-				Addresses:            []string{"127.0.0.1"},
-				OIDBatchSize:         10,
-				BQueueSize:           20,
-				SkipIndexFilesSearch: false,
-				IndexFileSize:        0,
-			},
-			shouldFail: true,
-			errMsg:     "IndexFileSize is not set",
-		},
 	}
 
 	for _, c := range cases {

pkg/config/blockfetcher_config.go

@@ -38,14 +38,8 @@ func (cfg *NeoFSBlockFetcher) Validate() error {
 	if err != nil {
 		return fmt.Errorf("invalid container ID: %w", err)
 	}
-	if cfg.BQueueSize < cfg.OIDBatchSize {
-		return fmt.Errorf("BQueueSize (%d) is lower than OIDBatchSize (%d)", cfg.BQueueSize, cfg.OIDBatchSize)
-	}
 	if len(cfg.Addresses) == 0 {
 		return errors.New("addresses are not set")
 	}
-	if !cfg.SkipIndexFilesSearch && cfg.IndexFileSize == 0 {
-		return errors.New("IndexFileSize is not set")
-	}
 	return nil
 }

pkg/services/blockfetcher/blockfetcher.go

@@ -16,6 +16,7 @@ import (
 	"github.com/nspcc-dev/neo-go/pkg/config"
 	"github.com/nspcc-dev/neo-go/pkg/core/block"
 	gio "github.com/nspcc-dev/neo-go/pkg/io"
+	"github.com/nspcc-dev/neo-go/pkg/network/bqueue"
 	"github.com/nspcc-dev/neo-go/pkg/services/oracle/neofs"
 	"github.com/nspcc-dev/neo-go/pkg/wallet"
 	"github.com/nspcc-dev/neofs-sdk-go/client"
@@ -34,9 +35,15 @@ const (
 	// defaultTimeout is the default timeout for NeoFS requests.
 	defaultTimeout = 5 * time.Minute
 	// defaultOIDBatchSize is the default number of OIDs to search and fetch at once.
-	defaultOIDBatchSize = 8000
+	defaultOIDBatchSize = bqueue.DefaultCacheSize
 	// defaultDownloaderWorkersCount is the default number of workers downloading blocks.
 	defaultDownloaderWorkersCount = 100
+	// defaultIndexFileSize is the default size of the index file.
+	defaultIndexFileSize = 128000
+	// defaultBlockAttribute is the default attribute name for block objects.
+	defaultBlockAttribute = "Block"
+	// defaultIndexFileAttribute is the default attribute name for index file objects.
+	defaultIndexFileAttribute = "Index"
 )
 
 // Constants related to NeoFS pool request timeouts.
@@ -151,8 +158,14 @@ func New(chain Ledger, cfg config.NeoFSBlockFetcher, logger *zap.Logger, putBloc
 	if cfg.DownloaderWorkersCount <= 0 {
 		cfg.DownloaderWorkersCount = defaultDownloaderWorkersCount
 	}
-	if len(cfg.Addresses) == 0 {
-		return nil, errors.New("no addresses provided")
+	if cfg.IndexFileSize <= 0 {
+		cfg.IndexFileSize = defaultIndexFileSize
+	}
+	if cfg.BlockAttribute == "" {
+		cfg.BlockAttribute = defaultBlockAttribute
+	}
+	if cfg.IndexFileAttribute == "" {
+		cfg.IndexFileAttribute = defaultIndexFileAttribute
 	}
 
 	params := pool.DefaultOptions()