Pause, resume and crashes

Why progress is safe

Rapidly splits a file into blocks of 256 KB. A block counts as done only after three things happen in this order:

1. the data is written to the file,
2. the file is flushed to the disk,
3. only then is the block recorded in the progress journal.

Because the record comes last, the journal can never say "done" about data that is not really there.

What happens on a power cut

After a crash or a power cut, Rapidly reads the journal and continues from the blocks that are really recorded. At worst it downloads again the last few seconds of work. You do not need to do anything; open Rapidly and the downloads carry on or wait for you, as you left them.

Resume checks

Before it continues, Rapidly asks the server whether the file is still the same one (by its tag and modification date). Three outcomes:

• Same file: it carries on.
• Changed file: it does not mix two versions. The partial file is moved aside and the download starts again from the beginning, and you are told.
• Weaker check: some servers give no tag or date. Rapidly carries on but marks the download "resumed with a weaker identity check". The final check at the end still applies.

Expired links

Many sites give links that stop working after a while. When a link expires, the download stops with a clear message and keeps what it has. Add a fresh link for the same file and Rapidly offers to continue the old download.

Waiting after errors

After a network error Rapidly waits a little and tries again. The wait grows each time but never passes 5 minutes. If a server keeps failing, Rapidly stops trying it for 60 seconds so it does not hammer the server, and then tries again.