Leverage the new chunked remotes to automatically resume downloads.
Sort of like rsync, although of course not as efficient since this
needs to start at a chunk boundry.
But, unlike rsync, this method will work for S3, WebDAV, external
special remotes, etc, etc. Only directory special remotes so far,
but many more soon!
This implementation will also properly handle starting a download
from one remote, interrupting, and resuming from another one, and so on.
(Resuming interrupted chunked uploads is similarly doable, although
slightly more expensive.)
This commit was sponsored by Thomas Djärv.
Needed for resuming from chunks.
Url keys are considered not stable. I considered treating url keys with a
known size as stable, but just don't feel that is enough information.
When chunk=0, always try the unchunked key first. This avoids the overhead
of needing to read the git-annex branch to find the chunkcount.
However, if the unchunked key is not present, go on and try the chunks.
Also, when removing a chunked key, update the chunkcounts even when
chunk=0.
No need to process each L.ByteString chunk, instead ask it to split.
Doesn't seem to have really sped things up much, but it also made the code
simpler.
Note that this does (and already did) buffer in memory. It seems that only
the directory special remote could take advantage of streaming chunks to
files w/o buffering, so probably won't add an interface to allow for that.
This will allow things like WebDAV to opean a single persistent connection
and reuse it for all the chunked data.
The crazy types allow for some nice code reuse.
Push it down from needing to be done in every Storer,
to being checked once inside ChunkedEncryptable.
Also, catch exceptions from PrepareStorer and PrepareRetriever,
just in case..
I'd have liked to keep these two concepts entirely separate,
but that are entagled: Storing a key in an encrypted and chunked remote
need to generate chunk keys, encrypt the keys, chunk the data, encrypt the
chunks, and send them to the remote. Similar for retrieval, etc.
So, here's an implemnetation of all of that.
The total win here is that every remote was implementing encrypted storage
and retrival, and now it can move into this single place. I expect this
to result in several hundred lines of code being removed from git-annex
eventually!
This commit was sponsored by Henrik Ahlgren.
Not yet used by any special remotes, but should not be too hard to add it
to most of them.
storeChunks is the hairy bit! It's loosely based on
Remote.Directory.storeLegacyChunked. The object is read in using a lazy
bytestring, which is streamed though, creating chunks as needed, without
ever buffering more than 1 chunk in memory.
Getting the progress meter update to work right was also fun, since
progress meter values are absolute. Finessed by constructing an offset
meter.
This commit was sponsored by Richard Collins.
This avoids a proliferation of hash directories when using new-style
chunking, and should improve performance since chunks are accessed
in sequence and so should have a common locality.
Of course, when a chunked key is encrypted, its hash directories have no
relation to the parent key.
This commit was sponsored by Christian Kellermann.
Slightly tricky as they are not normal UUIDBased logs, but are instead maps
from (uuid, chunksize) to chunkcount.
This commit was sponsored by Frank Thomas.
Moved old legacy chunking code, and cleaned up the directory and webdav
remotes use of it, so when no chunking is configured, that code is not
used.
The config for new style chunking will be chunk=1M instead of chunksize=1M.
There should be no behavior changes from this commit.
This commit was sponsored by Andreas Laas.
