feat(experimental): integrate writes strategy and appendable object writer #1695

Pulkit0110 · 2025-12-24T05:59:40Z

Integrate all the components required for bidi writes retries

gemini-code-assist · 2025-12-24T06:00:16Z

Summary of Changes

Hello @Pulkit0110, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly improves the robustness of asynchronous object operations in Google Cloud Storage by implementing a sophisticated retry and resumption system for bidirectional streaming. It introduces dedicated strategies to manage the state of ongoing read and write operations, automatically re-establishing streams and continuing data transfer from the last known good state in the event of transient network issues or server-side redirects. This ensures that applications using these experimental APIs can handle intermittent failures gracefully, leading to more reliable data transfers.

Highlights

Bidirectional Stream Retry Mechanism: Introduced a comprehensive retry mechanism for asynchronous bidirectional (bidi) streaming operations, specifically for object reads and writes, to enhance resilience against transient errors and redirects.
New Retry Strategies and Manager: Implemented a generic _BidiStreamRetryManager and specific _ReadResumptionStrategy and _WriteResumptionStrategy classes to manage the state, generate requests, and recover from failures during bidi stream retries.
Integration into Async Writers/Readers: Refactored AsyncAppendableObjectWriter and AsyncMultiRangeDownloader to integrate the new retry logic, allowing their open, append, and download_ranges methods to automatically handle retries and stream re-establishment.
Error Handling and State Recovery: Added predicates (_is_write_retryable, _is_read_retryable) to identify retryable exceptions and _on_open_error methods to extract routing tokens and handles from redirect errors, enabling intelligent state recovery.
Extensive Testing: Included new conformance tests for bidi reads to validate retry behavior under various fault injection scenarios, alongside new unit tests for the retry manager and both read/write resumption strategies.

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Code Review

This pull request introduces a significant and well-designed refactoring to integrate retry strategies for bidirectional reads and writes, enhancing the robustness of experimental asyncio features. The abstraction of retry logic into a _BidiStreamRetryManager and specific _WriteResumptionStrategy and _ReadResumptionStrategy classes is a solid architectural choice. The accompanying unit and conformance tests are comprehensive and provide good coverage for the new functionality. My review comments focus on improving error handling by replacing broad except Exception blocks with more specific ones and avoiding print() statements in library code.

gemini-code-assist · 2025-12-24T06:02:54Z

google/cloud/storage/_experimental/asyncio/async_appendable_object_writer.py

+            except Exception:
+                return False


The broad except Exception: can hide unexpected errors during the parsing of the status details. It would be better to catch a more specific exception, such as google.protobuf.message.DecodeError, to ensure other issues aren't silently ignored.

gemini-code-assist · 2025-12-24T06:02:54Z

google/cloud/storage/_experimental/asyncio/async_appendable_object_writer.py

+                    except Exception:
+                        # Could not parse the error, ignore
+                        pass


Using a broad except Exception: is risky as it can mask bugs. Please consider catching a more specific exception, like google.protobuf.message.DecodeError, to make the error handling more robust. Silently passing on any exception could hide important issues.

gemini-code-assist · 2025-12-24T06:02:54Z

google/cloud/storage/_experimental/asyncio/async_multi_range_downloader.py

+            except Exception as e:
+                print(f"--- Error parsing status_details_bin: {e}")
+                return False


Printing to stdout is generally discouraged in a library as it can pollute the application's output. It would be better to use the logging module to log this error. Also, catching a broad Exception can hide other issues. It would be better to catch a more specific exception, such as google.protobuf.message.DecodeError.

gemini-code-assist · 2025-12-24T06:02:54Z

google/cloud/storage/_experimental/asyncio/async_multi_range_downloader.py

+                    except Exception as e:
+                        print(f"--- Error unpacking redirect in _on_open_error: {e}")


Printing to stdout here should be avoided in a library. Please consider using the logging module instead. Additionally, catching a broad Exception is risky. It would be more robust to catch a specific exception, like google.protobuf.message.DecodeError.

gemini-code-assist · 2025-12-24T06:02:54Z

google/cloud/storage/_experimental/asyncio/retry/reads_resumption_strategy.py

+                    except Exception as e:
+                        print(f"--- Error unpacking redirect in _on_open_error: {e}")


Printing to stdout should be avoided in a library. It's better to use the logging module for such errors. Also, catching a broad Exception can hide other potential issues. Please consider catching a more specific exception, like google.protobuf.message.DecodeError.

gemini-code-assist · 2025-12-24T06:02:54Z

google/cloud/storage/_experimental/asyncio/retry/writes_resumption_strategy.py

+                    except Exception:
+                        # Could not parse the error, ignore
+                        pass


Using a broad except Exception: can hide unexpected errors. It would be more robust to catch a specific exception, such as google.protobuf.message.DecodeError, to avoid silently ignoring other potential problems during parsing.

…riter

chandra-siri · 2026-01-13T07:22:29Z

google/cloud/storage/_experimental/asyncio/async_appendable_object_writer.py

+            BidiWriteObjectRedirectedError
+        ),
+    ):
+        logger.info(f"Retryable write exception encountered: {exc}")


make it warning

chandra-siri · 2026-01-13T07:24:39Z

google/cloud/storage/_experimental/asyncio/async_appendable_object_writer.py

+                    if detail.type_url == _BIDI_WRITE_REDIRECTED_TYPE_URL:
+                        return True
+            except Exception:
+                logger.error("Error unpacking redirect details from gRPC error.")


add Exception details in log

chandra-siri · 2026-01-14T07:40:03Z

google/cloud/storage/_experimental/asyncio/async_appendable_object_writer.py

        self.flush_interval = writer_options.get(
            "FLUSH_INTERVAL_BYTES", _DEFAULT_FLUSH_INTERVAL_BYTES
        )
        # TODO: add test case for this.


remove this unwanted TODO.

chandra-siri · 2026-01-15T10:35:43Z

google/cloud/storage/_experimental/asyncio/retry/_helpers.py

    return routing_token, read_handle
+
+
+def _extract_bidi_writes_redirect_proto(exc: Exception):


this method is almost same as _handle_redirect method. Please merge both of them. Also please refer to this comment

chandra-siri · 2026-01-15T10:38:28Z

google/cloud/storage/_experimental/asyncio/async_appendable_object_writer.py

+            self.persisted_size = response.persisted_size
+            return self.persisted_size
+
+    def _on_open_error(self, exc):


Please use the same method which is defined in MRD 's _on_open_error -

by moving it to _retry/helpers.py

Please refer to this comment

chandra-siri · 2026-01-15T10:45:16Z

google/cloud/storage/_experimental/asyncio/async_appendable_object_writer.py

+                    try:
+                        await self.write_obj_stream.close()
+                    except Exception:  # ignore cleanup errors
+                        pass


log warning

chandra-siri · 2026-01-15T10:57:02Z

google/cloud/storage/_experimental/asyncio/async_appendable_object_writer.py

-        total_bytes = len(data)
-        if total_bytes == 0:
-            # TODO: add warning.
+        if not data:


log.debug("Empty bytes sent")

chandra-siri · 2026-01-15T11:03:00Z

google/cloud/storage/_experimental/asyncio/async_appendable_object_writer.py

+logger = logging.getLogger(__name__)
+
+
+def _is_write_retryable(exc):


Please merge this and _is_read_retryable and move comment code to _helpers.py

chandra-siri · 2026-01-15T11:27:51Z

google/cloud/storage/_experimental/asyncio/async_appendable_object_writer.py

+        write_state.persisted_size = self.persisted_size
+        write_state.bytes_sent = self.persisted_size


If both are self.persisted_size , then why do we need 2 variables ?

chandra-siri · 2026-01-15T11:45:51Z

google/cloud/storage/_experimental/asyncio/async_appendable_object_writer.py

+                        requests = strategy.generate_requests(state)
+
+                    num_requests = len(requests)


observed regression in appends might be because of this, generating all at sending one by one.

instead try making generate_requests an true generator (ie have yield instead of return)

product-auto-label bot added size: xl Pull request size is extra large. api: storage Issues related to the googleapis/python-storage API. labels Dec 24, 2025

gemini-code-assist bot reviewed Dec 24, 2025

View reviewed changes

Pulkit0110 force-pushed the bidi-writes-retry-integrate branch from c3ba20d to 36a02d7 Compare January 2, 2026 10:57

product-auto-label bot added size: l Pull request size is large. and removed size: xl Pull request size is extra large. labels Jan 2, 2026

Pulkit0110 added 7 commits January 12, 2026 09:35

integrate retry logic with the MRD

4c4079a

feat(experimental): add write resumption strategy

c7f6d46

address gemini bot comments

c0350f5

feat(experimental): integrate writes strategy and appendable object w…

d1cc1ef

…riter

more changes

ccf667a

adding unit tests

c131588

adding more unit tests

5d39296

Pulkit0110 force-pushed the bidi-writes-retry-integrate branch from 36a02d7 to 5d39296 Compare January 13, 2026 06:53

product-auto-label bot added size: xl Pull request size is extra large. and removed size: l Pull request size is large. labels Jan 13, 2026

Pulkit0110 marked this pull request as ready for review January 13, 2026 06:59

Pulkit0110 requested review from a team as code owners January 13, 2026 06:59

blunderbuss-gcf bot assigned chandra-siri Jan 13, 2026

Pulkit0110 added 3 commits January 13, 2026 09:17

fix lint errors

e8696d7

refactor unit tests

8c81047

fix lint errors

ad68e91

chandra-siri requested changes Jan 15, 2026

View reviewed changes

		except Exception as e:
		print(f"--- Error unpacking redirect in _on_open_error: {e}")

		return routing_token, read_handle


		def _extract_bidi_writes_redirect_proto(exc: Exception):

		logger = logging.getLogger(__name__)


		def _is_write_retryable(exc):

		write_state.persisted_size = self.persisted_size
		write_state.bytes_sent = self.persisted_size

		requests = strategy.generate_requests(state)

		num_requests = len(requests)

feat(experimental): integrate writes strategy and appendable object writer #1695

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Pulkit0110 commented Dec 24, 2025

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