Large PUT/POST uploads (>60MB) fail with context canceled when an nginx
reverse proxy sits in front of oauth2-proxy. The root cause is that
http.Transport inherits Go's default 4KB WriteBufferSize, requiring
~15,000 write syscalls for a 60MB upload. This generates backpressure
on the nginx->oauth2-proxy pipe. Once nginx hits proxy_read_timeout
between consecutive write ops, it closes the connection, canceling
req.Context(), which propagates as context canceled on the in-flight
RoundTrip to the upstream.
Expose writeBufferSize and readBufferSize on the Upstream config struct,
wired to transport.WriteBufferSize and transport.ReadBufferSize in
newReverseProxy. Both default to 0 (preserving current behavior, Go
uses 4KB). Setting writeBufferSize to 65536 (64KB) reduces write
syscalls by 16x and resolves the timeout correlation for large uploads.
Fixes#3389
Signed-off-by: Mateen Anjum <mateenali66@gmail.com>
c2a5dfa4ea