David Turner <dtur...@twosigma.com> writes: > In the event that a HTTP server closes the connection after giving a > 200 but before giving any packets, we don't want to hang forever > waiting for a response that will never come. Instead, we should die > immediately. > > One case where this happens is when attempting to fetch a dangling > object by SHA. > > Prior to this patch, fetch-pack would wait for more data from the > server, and remote-curl would wait for fetch-pack, causing a deadlock. > > Despite this patch, there is other possible malformed input that could > cause the same deadlock (e.g. a half-finished pktline, or a pktline but > no trailing flush). There are a few possible solutions to this: > > 1. Allowing remote-curl to tell fetch-pack about the EOF (so that > fetch-pack could know that no more data is coming until it says > something else). This is tricky because an out-of-band signal would > be required, or the http response would have to be re-framed inside > another layer of pkt-line or something. > > 2. Make remote-curl understand some of the protocol. It turns out > that in addition to understanding pkt-line, it would need to watch for > ack/nak. This is somewhat fragile, as information about the protocol > would end up in two places. Also, pkt-lines which are already at the > length limit would need special handling. > > Both of these solutions would require a fair amount of work, whereas > this hack is easy and solves at least some of the problem. > > Still to do: it would be good to give a better error message > than "fatal: The remote end hung up unexpectedly".
It seems to me that there is some gap/leap in the description between the second and third paragraph above (i.e. the client asks for an object, the server tries to see if the object is reachable from the refs, and then what? who waits for more data without asking?), but other than that, including the future direction, the proposed log message is very nicely described. Thanks, will queue.
