revert fallback changes in ota_cache

Author: Bodong-Yang

src/ota_proxy/ota_cache.py

@@ -55,8 +55,6 @@
 from .errors import (
     BaseOTACacheError,
     CacheCommitFailed,
-    CacheProviderNotReady,
-    ReaderPoolBusy,
 )
 from .external_cache import mount_external_cache, umount_external_cache
 from .lru_cache_helper import LRUCacheHelper
@@ -695,50 +693,39 @@ async def retrieve_file(
                 raw_url, headers=headers_from_client
             )
 
-        try:
-            # NOTE(20241202): behavior changed: even if _cache_enabled is False, if external_cache is configured
-            #   and loaded, still try to use external cache source.
-            if self._external_cache_data_dir and (
-                _res := await self._retrieve_file_by_external_cache(
-                    cache_policy, self._external_cache_data_dir
-                )
-            ):
-                self._metrics_data.cache_external_hits += 1
-                return _res
-
-            # NOTE(20251212): use local cache first before going to NFS cache
-            if not cache_policy.retry_caching and (
-                _res := await self._retrieve_file_by_cache_lookup(
-                    raw_url=raw_url, cache_policy=cache_policy
-                )
-            ):
-                self._metrics_data.cache_local_hits += 1
-                return _res
+        # NOTE(20241202): behavior changed: even if _cache_enabled is False, if external_cache is configured
+        #   and loaded, still try to use external cache source.
+        if self._external_cache_data_dir and (
+            _res := await self._retrieve_file_by_external_cache(
+                cache_policy, self._external_cache_data_dir
+            )
+        ):
+            self._metrics_data.cache_external_hits += 1
+            return _res
 
-            if self._external_nfs_cache_data_dir and (
-                _res := await self._retrieve_file_by_external_cache(
-                    cache_policy, self._external_nfs_cache_data_dir
-                )
-            ):
-                self._metrics_data.cache_external_nfs_hits += 1
-                return _res
-
-            if _res := await self._retrieve_file_by_new_caching(
-                raw_url=raw_url,
-                cache_policy=cache_policy,
-                headers_from_client=headers_from_client,
-            ):
-                return _res
-        except (ReaderPoolBusy, CacheProviderNotReady):
-            raise  # common errors, will indicate server_app to return 503
-        except Exception as e:
-            # NOTE(20260403): sometime the caching might fail due to cache bucket too
-            #                 shallow, LRU crushing the cache files too fast under multi-client
-            #                 condition.
-            burst_suppressed_logger_exc.exception(
-                f"internal errors when processing {raw_url}: {e!r}\n"
-                "fallback to direct downloading ..."
+        # NOTE(20251212): use local cache first before going to NFS cache
+        if not cache_policy.retry_caching and (
+            _res := await self._retrieve_file_by_cache_lookup(
+                raw_url=raw_url, cache_policy=cache_policy
             )
+        ):
+            self._metrics_data.cache_local_hits += 1
+            return _res
+
+        if self._external_nfs_cache_data_dir and (
+            _res := await self._retrieve_file_by_external_cache(
+                cache_policy, self._external_nfs_cache_data_dir
+            )
+        ):
+            self._metrics_data.cache_external_nfs_hits += 1
+            return _res
+
+        if _res := await self._retrieve_file_by_new_caching(
+            raw_url=raw_url,
+            cache_policy=cache_policy,
+            headers_from_client=headers_from_client,
+        ):
+            return _res
 
         # as last resort, finally try to handle the request by directly downloading
         return await self._retrieve_file_by_downloading(