Refa:replace trio with asyncio (#11831)

### What problem does this PR solve?

change:
replace trio with asyncio

### Type of change
- [x] Refactoring

rag/flow/hierarchical_merger/hierarchical_merger.py

@@ -13,13 +13,13 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
+import asyncio
+import logging
 import random
 import re
 from copy import deepcopy
 from functools import partial
 
-import trio
-
 from common.misc_utils import get_uuid
 from rag.utils.base64_image import id2image, image2id
 from deepdoc.parser.pdf_parser import RAGFlowPdfParser
@@ -178,9 +178,18 @@ class HierarchicalMerger(ProcessBase):
                 }
                 for c, img in zip(cks, images)
             ]
-            async with trio.open_nursery() as nursery:
-                for d in cks:
-                    nursery.start_soon(image2id, d, partial(settings.STORAGE_IMPL.put, tenant_id=self._canvas._tenant_id), get_uuid())
+            tasks = []
+            for d in cks:
+                tasks.append(asyncio.create_task(image2id(d, partial(settings.STORAGE_IMPL.put, tenant_id=self._canvas._tenant_id), get_uuid())))
+            try:
+                await asyncio.gather(*tasks, return_exceptions=False)
+            except Exception as e:
+                logging.error(f"Error in image2id: {e}")
+                for t in tasks:
+                    t.cancel()
+                await asyncio.gather(*tasks, return_exceptions=True)
+                raise
+
             self.set_output("chunks", cks)
 
         self.callback(1, "Done.")