SNOW-3869839: Treat S3 HEAD 403 as file-not-found in preflight upload check - #2987
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SNOW-3869839: Treat S3 HEAD 403 as file-not-found in preflight upload check#2987sfc-gh-turbaszek wants to merge 3 commits into
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… check S3 returns 403 (instead of 404) for a HEAD request on a non-existent key when the caller's credentials lack s3:ListBucket on the bucket. The scoped credentials Snowflake issues for internal-stage PUTs grant PutObject/ GetObject on the prefix but not bucket-level ListBucket, so the connector's pre-flight existence check was raising a hard 403 error even though the subsequent PUT would succeed. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
The preflight HEAD result is only consulted when meta.overwrite is False,
so treating an ambiguous 403 as "file absent" in that case would upload
over a file the user asked us to keep, silently breaking
PUT ... OVERWRITE = FALSE. Restrict the 403 tolerance to the case where
the file is going to be overwritten anyway - where the answer cannot
change what happens next - and keep raising otherwise. This also leaves
the download preflight, where overwrite is False, reporting genuine
permission failures instead of "not found".
When the 403 is raised, log a warning naming the likely cause (missing
s3:ListBucket) and both remedies, since a bare "403 Client Error:
Forbidden" is what made this hard to diagnose in the first place. Also
include the status code in the not-found debug line so 404 ("absent") is
distinguishable from 403 ("assuming absent") in logs.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #2987 +/- ##
==========================================
+ Coverage 65.04% 65.13% +0.09%
==========================================
Files 123 123
Lines 17413 17438 +25
Branches 2387 2394 +7
==========================================
+ Hits 11326 11359 +33
+ Misses 5648 5639 -9
- Partials 439 440 +1 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
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Summary
PUTuploads to S3-backed internal stages could fail with403 Client Error: Forbiddenon the pre-flight existence check (get_file_header()→HEAD), even though the underlyingPUTwould have succeeded.403(not404) forHeadObjecton a non-existent key when the caller lackss3:ListBucketon the bucket — which is the case for the scoped STS credentials Snowflake issues for stage uploads (they grantPutObject/GetObjecton the prefix but not bucket-levelListBucket).get_file_header()(sync and async S3 storage clients) now treats403the same as404— i.e. "cannot confirm the file exists, proceed to upload" — instead of raising.Test plan
test_get_header_403_treated_as_not_foundtotest/unit/test_s3_util.pyandtest/unit/aio/test_s3_util_async.pytest/unit/test_s3_util.pyandtest/unit/aio/test_s3_util_async.pysuites — all passingDESCRIPTION.mdchangelogFixes SNOW-3869839.
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