[#922] storage engine: Prevent any operations after first Close call

Make `BlockExecution` / `ResumeExecution` to not release per-shard worker
pools. Make `StorageEngine.Close` to block these methods and any
data-related operations. It is still releases the pools.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/local_object_storage/engine/control.go

@@ -42,7 +42,7 @@ func (e *StorageEngine) Init() error {
 var errClosed = errors.New("storage engine is closed")
 
 // Close releases all StorageEngine's components. Waits for all data-related operations to complete.
-// After the call, all the next ones will fail until the ResumeExecution call.
+// After the call, all the next ones will fail.
 //
 // The method is supposed to be called when the application exits.
 func (e *StorageEngine) Close() error {
@@ -50,12 +50,14 @@ func (e *StorageEngine) Close() error {
 }
 
 // closes all shards. Never returns an error, shard errors are logged.
-func (e *StorageEngine) close() error {
+func (e *StorageEngine) close(releasePools bool) error {
 	e.mtx.RLock()
 	defer e.mtx.RUnlock()
 
-	for _, p := range e.shardPools {
+	if releasePools {
-		p.Release()
+		for _, p := range e.shardPools {
+			p.Release()
+		}
 	}
 
 	for id, sh := range e.shards {
@@ -85,7 +87,8 @@ func (e *StorageEngine) execIfNotBlocked(op func() error) error {
 }
 
 // sets the flag of blocking execution of all data operations according to err:
-//   * err != nil, then blocks the execution. If exec wasn't blocked, calls close method.
+//   * err != nil, then blocks the execution. If exec wasn't blocked, calls close method
+//     (if err == errClosed => additionally releases pools and does not allow to resume executions).
 //   * otherwise, resumes execution. If exec was blocked, calls open method.
 //
 // Can be called concurrently with exec. In this case it waits for all executions to complete.
@@ -95,6 +98,11 @@ func (e *StorageEngine) setBlockExecErr(err error) error {
 
 	prevErr := e.blockExec.err
 
+	wasClosed := errors.Is(prevErr, errClosed)
+	if wasClosed {
+		return errClosed
+	}
+
 	e.blockExec.err = err
 
 	if err == nil {
@@ -102,7 +110,7 @@ func (e *StorageEngine) setBlockExecErr(err error) error {
 			return e.open()
 		}
 	} else if prevErr == nil { // ok -> block
-		return e.close()
+		return e.close(errors.Is(err, errClosed))
 	}
 
 	// otherwise do nothing
@@ -115,7 +123,7 @@ func (e *StorageEngine) setBlockExecErr(err error) error {
 //
 // Сan be called regardless of the fact of the previous blocking. If execution wasn't blocked, releases all resources
 // similar to Close. Can be called concurrently with Close and any data related method (waits for all executions
-// to complete).
+// to complete). Returns error if any Close has been called before.
 //
 // Must not be called concurrently with either Open or Init.
 //
@@ -130,7 +138,7 @@ func (e *StorageEngine) BlockExecution(err error) error {
 //
 // Сan be called regardless of the fact of the previous blocking. If execution was blocked, prepares all resources
 // similar to Open. Can be called concurrently with Close and any data related method (waits for all executions
-// to complete).
+// to complete). Returns error if any Close has been called before.
 //
 // Must not be called concurrently with either Open or Init.
 func (e *StorageEngine) ResumeExecution() error {

pkg/local_object_storage/engine/control_test.go

@@ -0,0 +1,46 @@
+package engine
+
+import (
+	"errors"
+	"testing"
+
+	cidtest "github.com/nspcc-dev/neofs-api-go/pkg/container/id/test"
+	"github.com/stretchr/testify/require"
+)
+
+func TestExecBlocks(t *testing.T) {
+	e := testNewEngineWithShardNum(t, 2) // number doesn't matter in this test, 2 is several but not many
+	defer e.Close()
+
+	// put some object
+	obj := generateRawObjectWithCID(t, cidtest.Generate()).Object()
+
+	addr := obj.Address()
+
+	require.NoError(t, Put(e, obj))
+
+	// block executions
+	errBlock := errors.New("block exec err")
+
+	require.NoError(t, e.BlockExecution(errBlock))
+
+	// try to exec some op
+	_, err := Head(e, addr)
+	require.ErrorIs(t, err, errBlock)
+
+	// resume executions
+	require.NoError(t, e.ResumeExecution())
+
+	_, err = Head(e, addr) // can be any data-related op
+	require.NoError(t, err)
+
+	// close
+	require.NoError(t, e.Close())
+
+	// try exec after close
+	_, err = Head(e, addr)
+	require.Error(t, err)
+
+	// try to resume
+	require.Error(t, e.ResumeExecution())
+}

pkg/local_object_storage/engine/engine_test.go

@@ -116,3 +116,13 @@ func addAttribute(obj *object.RawObject, key, val string) {
 	attrs = append(attrs, attr)
 	obj.SetAttributes(attrs...)
 }
+
+func testNewEngineWithShardNum(t *testing.T, num int) *StorageEngine {
+	shards := make([]*shard.Shard, 0, num)
+
+	for i := 0; i < num; i++ {
+		shards = append(shards, testNewShard(t, i))
+	}
+
+	return testNewEngineWithShards(shards...)
+}

pkg/local_object_storage/engine/inhume_test.go

@@ -34,7 +34,7 @@ func TestStorageEngine_Inhume(t *testing.T) {
 	link.SetSplitID(splitID)
 
 	t.Run("delete small object", func(t *testing.T) {
-		e := testNewEngineWithShards(testNewShard(t, 1))
+		e := testNewEngineWithShardNum(t, 1)
 		defer e.Close()
 
 		err := Put(e, parent.Object())