streamFromVolumeServers wrote the 200/206 status from filer metadata
before any byte had been fetched from a volume server, so a missing or
corrupted needle surfaced as a broken 200 body and the request metrics
recorded a success. Defer the status commit to the first body write: a
failed first read now returns a clean 500 before headers, while the
wire timing of successful responses is unchanged since net/http buffers
the status line until body bytes arrive anyway.
Chris LuandGitHub
d9d5fab35b