[Bug]: Google Storage broken in Run:ai model streamer

[bkauf]

Your current environment

vllm/vllm-openai/nightly-8bff831f0aa239006f34b721e63e1340e3472067

🐛 Describe the bug

PR #27308 introduced a bug that breaks the Google cloud storage integration when using the Run:ai model streamer. The bug is because of method is_s3 which is used here
It is only checking S3:// path when gs:// is also a valid path

[dsikka]

Can we add tests to the ci that can capture this case?

This pathway seems to constantly break and fixes are landed without additional testing being added to prevent it from happening again.

I don’t believe anything was flagged when the PR of concern landed.

[noa-neria]

@simon-mo will #27308 be included in the upcoming 11.1 ?

[dsikka]

@rahul-tuli Can we add a fix for this case?
@bkauf Please suggest a test case we can add to the CI to prevent this from happening again.

[FWKMultiverse]

The main problem is that the is_s3() function only checks for s3://, but code in vLLM may encounter a path as gs:// (Google Cloud Storage), which could result in Google Cloud Storage being considered non-S3, causing the maybe_override_with_speculators function to malfunction.

The solution is to extend the is_s3() function to cover both s3:// and gs://, or create a new function, such as is_cloud_storage().

def is_cloud_storage(model_or_path: str) -> bool:
    """Check if path is S3 or Google Cloud Storage."""
    lower_path = model_or_path.lower()
    return lower_path.startswith("s3://") or lower_path.startswith("gs://")

Then change the call to action:

from

if not is_s3(self.model):

is

if not is_cloud_storage(self.model):