[#253] pool: Don't count regular FrostFS errors

Previously we count all frostfs errors like:
ObjectNotFound, EACLNotFound
because frostfs status is unconditionally resolved into built-in go errors
but handleError method handled built-in errors like internal network ones.
Since after resolving frostfs errors status is also returned we start check this first

Signed-off-by: Denis Kirillov <d.kirillov@yadro.com>

pool/pool.go

@@ -1227,6 +1227,22 @@ func (c *clientWrapper) close() error {
 }
 
 func (c *clientStatusMonitor) handleError(ctx context.Context, st apistatus.Status, err error) error {
+	if stErr := apistatus.ErrFromStatus(st); stErr != nil {
+		switch stErr.(type) {
+		case *apistatus.ServerInternal,
+			*apistatus.WrongMagicNumber,
+			*apistatus.SignatureVerification,
+			*apistatus.NodeUnderMaintenance:
+			c.incErrorRate()
+		}
+
+		if err == nil {
+			err = stErr
+		}
+
+		return err
+	}
+
 	if err != nil {
 		if needCountError(ctx, err) {
 			c.incErrorRate()
@@ -1235,16 +1251,7 @@ func (c *clientStatusMonitor) handleError(ctx context.Context, st apistatus.Stat
 		return err
 	}
 
-	err = apistatus.ErrFromStatus(st)
-	switch err.(type) {
-	case *apistatus.ServerInternal,
-		*apistatus.WrongMagicNumber,
-		*apistatus.SignatureVerification,
-		*apistatus.NodeUnderMaintenance:
-		c.incErrorRate()
-	}
-
-	return err
+	return nil
 }
 
 func needCountError(ctx context.Context, err error) bool {

pool/pool_test.go

@@ -609,6 +609,23 @@ func TestHandleError(t *testing.T) {
 			expectedError: true,
 			countError:    false,
 		},
+		{
+			ctx:           ctx,
+			status:        new(apistatus.ObjectNotFound),
+			err:           &apistatus.ObjectNotFound{},
+			expectedError: true,
+			countError:    false,
+		},
+		{
+			ctx:           ctx,
+			status:        nil,
+			err:           &apistatus.EACLNotFound{},
+			expectedError: true,
+			// we expect error be counted because status is nil
+			// currently we assume that DisableFrostFSErrorResolution be always false for pool
+			// and status be checked first in handleError
+			countError: true,
+		},
 		{
 			ctx:           ctx,
 			status:        new(apistatus.ServerInternal),