Hey,
> A second issue is caused when a build product download is started, then > aborted. In that case, sendfile throws an exception or enters an endless > loop. Ok, so I found a couple of errors here. First, I noticed that it was not possible to download simultaneously two build products, because the first download was blocking the whole process. This is solved by: 6ad9c602697ffe33c8fbb09ccd796b74bf600223. In short, current-fiber was set to #f, both in the context of the caller and the spawned thread. So I think the get-message operating was blocking the whole thread instead of suspending the current fiber. But if someone else could take a look it would be nice :). Second issue, sendfile may throw EPIPE or ECONNRESET if the client disconnects before the end of the transfer. I think, besides the dirty backtrace, it was not harmful. But anyway, its better to catch this as we are doing in "guix publish", see: 0955a11abd9e27c96a1375cca6a1c97869b5780a. I fear it won't be enough to fix the 504 errors, but at least it's a start. Thanks, Mathieu
