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seaweedfs/weed/remote_storage
Chris Lu b763a5f6bf s3: improve TTFB for large remote objects (#10010)
* s3: add streaming reader interface for remote storage

Add RemoteStorageStreamReader optional interface to support efficient
streaming of large remote objects without buffering entire file in memory.
This enables future stream-through caching where data can be served to
clients while simultaneously writing to volume servers.

Implement ReadFileAsStream() for S3, GCS, and Azure backends using their
native streaming APIs. This provides the foundation for improving TTFB
on large remote file access by serving data directly from remote storage
while background cache operation populates local chunks.

The streaming interface allows remote storage backends to return io.ReadCloser,
enabling efficient memory usage for multi-GB objects compared to the
current ReadFile() approach which buffers entire ranges in memory.

* s3: adaptive timeout for remote object caching to improve TTFB

Use size-aware cache polling timeout to balance cache-hit rate against
time-to-first-byte:

- Small files (<50MB): 10s timeout - more likely to complete caching
  before timeout, improving subsequent request performance
- Medium files (50-500MB): 5s timeout - default balance
- Large files (>500MB): 2s timeout - fail-fast to improve initial TTFB
  for very large downloads

This reduces waiting time for large remote files while maintaining
high cache-hit rate for smaller files that cache quickly.

* s3: address code review feedback for stream-through cache

- Move startBackgroundRemoteCache call after policy recheck to avoid
  cache side effects for denied requests (authorization first)
- Make startBackgroundRemoteCache version-aware by accepting versionId
  parameter and using buildVersionedRemoteObjectPath
- Add timeout (5 minutes) to background cache context to prevent
  goroutine pile-up if RPC stalls under load
- Update cacheRemoteObjectForStreamingWithShortTimeout to return both
  entry and error, allowing callers to distinguish transient errors
  (timeout/cancellation) from permanent errors (not found, denied)
- Update streamFromVolumeServers to handle permanent cache errors with
  appropriate HTTP status codes (404 for not found, 503 for transient)
2026-06-18 17:22:32 -07:00
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