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fix: fix a race condition caused due to concurrent writes #785

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fix: fix a race condition caused due to concurrent writes #785

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42afdd3
fix: fix a race condition caused due to concurrent writes
nidhiii-27 Mar 31, 2026
a01297c
fix: add thread locking
nidhiii-27 Mar 31, 2026
ac28573
fix lint
nidhiii-27 Mar 31, 2026
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19 changes: 13 additions & 6 deletions gcs/upload.py
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
import hashlib
import itertools
import json
import threading
import types
import uuid

Expand Down Expand Up @@ -58,6 +59,7 @@ def init(cls, request, metadata, bucket, location, upload_id):
media=b"",
complete=False,
transfer=set(),
lock=threading.Lock(),
)

@classmethod
Expand Down Expand Up @@ -585,7 +587,8 @@ def update_upload_checksums(upload_metadata, object_checksums):
# Currently, the testbench will always checkpoint and flush data for testing purposes,
# instead of the 15 seconds interval used in the GCS server.
# TODO(#592): Refactor testbench checkpointing to more closely follow GCS server behavior.
upload.media += content
with upload.lock:
upload.media += content

# Update appendable blob size and media here, as part of #720.
# TODO(#720): (a) Update crc and update_time in object metadata.
Expand All @@ -595,9 +598,11 @@ def update_upload_checksums(upload_metadata, object_checksums):
update_upload_checksums(upload.metadata, object_checksums)

def update_appendable_blob(blob, unused_generation):
blob.media = upload.media
blob.metadata.size = len(upload.media)
blob.metadata.checksums.crc32c = crc32c.crc32c(upload.media)
with upload.lock:
snapshot = bytes(upload.media)
blob.media = snapshot
blob.metadata.size = len(snapshot)
blob.metadata.checksums.crc32c = crc32c.crc32c(snapshot)
return blob

blob = db.do_update_object(
Expand Down Expand Up @@ -632,11 +637,13 @@ def update_appendable_blob(blob, unused_generation):
if is_appendable:

def finalize_blob(blob, unused_generation):
blob.media = upload.media
with upload.lock:
snapshot = bytes(upload.media)
blob.media = snapshot
blob.metadata.finalize_time.FromDatetime(
datetime.datetime.now(datetime.timezone.utc)
)
blob.metadata.size = len(upload.media)
blob.metadata.size = len(snapshot)
blob.upload = None
blob.upload_gen = 0
return blob
Expand Down
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