77a8a4455d
An SLO PUT requires that we HEAD every referenced object; as a result, it can be a very time-intensive operation. This makes it difficult as a client to differentiate between a proxy-server that's still doing work and one that's crashed but left the socket open. Now, clients can opt-in to receiving heartbeats during long-running PUTs by including the query parameter heartbeat=on With heartbeating turned on, the proxy will start its response immediately with 202 Accepted then send a single whitespace character periodically until the request completes. At that point, a final summary chunk will be sent which includes a "Response Status" key indicating success or failure and (if successful) an "Etag" key indicating the Etag of the resulting SLO. This mechanism is very similar to the way bulk extractions and deletions work, and even the way SLO behaves for ?multipart-manifest=delete requests. Note that this is opt-in: this prevents us from sending the 202 response to existing clients that may mis-interpret it as an immediate indication of success. Co-Authored-By: Alistair Coles <alistairncoles@gmail.com> Related-Bug: 1718811 Change-Id: I65cee5f629c87364e188aa05a06d563c3849c8f3