Errors when processing gsutil -m -q setmeta - google-cloud-storage

Question

When processing the command:
gsutil -m -q setmeta -h "Cache-Control:public, max-age=10"
I get these errors frequently:
ERROR 1028 16:10:46.257674 retry_decorator.py] Retrying in 0.94 seconds ...
Traceback (most recent call last):
File "/usr/local/share/google/google-cloud-sdk/platform/gsutil/third_party/retry-decorator/retry_decorator/retry_decorator.py", line 20, in f_retry
return f(*args, **kwargs)
File "/usr/local/share/google/google-cloud-sdk/platform/gsutil/gslib/commands/setmeta.py", line 248, in SetMetadataFunc
provider=exp_src_url.scheme)
File "/usr/local/share/google/google-cloud-sdk/platform/gsutil/gslib/cloud_api_delegator.py", line 212, in PatchObjectMetadata
generation=generation, preconditions=preconditions, fields=fields)
File "/usr/local/share/google/google-cloud-sdk/platform/gsutil/gslib/gcs_json_api.py", line 819, in PatchObjectMetadata
generation=generation)
File "/usr/local/share/google/google-cloud-sdk/platform/gsutil/gslib/gcs_json_api.py", line 1308, in _TranslateExceptionAndRaise
raise translated_exception
PreconditionException: PreconditionException: 412 Precondition Failed
The server is on Google Compute engine and is updated frequently with:
gcloud components update
It seems the process actually completes but these errors keep occurring. Any idea what causes them and if there is a solution?
Thanks.

Answer 1

This can occur for two reasons:
Another client updated the object (or its metadata) concurrently.
There was a transient service or network error that needed to be retried (thus the "Retrying" message), but the original request actually succeeded. The retry gets preconditioned against the original object's metageneration, so it fails, even though the original operation succeeded.
If the cause is #1, you can solve it by avoiding concurrent updates to the objects. If the cause is #2, unfortunately, there is not much you can do.