This is seriously super hairy. It has to handle interrupted exports,
which may be resumed with the same or a different tree. It also has to
recover from export conflicts, which could cause the wrong content
to be renamed to a file.
I think this works, or is close to working. See the update to the design
for how it works.
This is definitely not optimal, in that it does more renames than are
necessary. It would probably be worth finding the keys that are really
renamed and only renaming those. But let's get the "simple" approach to
work first..
This commit was supported by the NSF-funded DataLad project.
Not yet used, but essential for resuming cleanly.
Note that, in normmal operation, only one commit is made to export.log
during an export; the incomplete version only gets to the journal and
is then overwritten.
This commit was supported by the NSF-funded DataLad project.
Straightforward enough, except for the needed belt-and-suspenders sanity
checks to avoid foot shooting due to exports not being key/value stores.
* Even when annex.verify=false, always verify from exports.
* Only get files from exports that use a backend that supports
checksum verification.
* Never trust exports, even if the user says to, because then
`git annex drop` would drop content if the export seemed to contain
a copy.
This commit was supported by the NSF-funded DataLad project.
Removed uncorrect UniqueKey key in db schema; a key can appear multiple
times with different files.
The database has to be flushed after each removal. But when adding files
to the export, lots of changes are able to be queued up w/o flushing.
So it's still fairly efficient.
If large removals of files from exports are too slow, an alternative
would be to make two passes over the diff, one pass queueing deletions
from the database, then a flush and the a second pass updating the
location log. But that would use more memory, and need to look up
exportKey twice per removed file, so I've avoided such optimisation yet.
This commit was supported by the NSF-funded DataLad project.
Went with a separate db per export remote, rather than a single export
database. Mostly because there will probably not be a lot of separate
export remotes, and it might be convenient to be able to delete a given
remote's export database.
This commit was supported by the NSF-funded DataLad project.
* Only export to remotes that were initialized to support it.
* Prevent storing key/value on export remotes.
* Prevent enabling exporttree=yes and encryption in the same remote.
SetupStage Enable was changed to take the old RemoteConfig.
This allowed only setting exporttree when initially setting up a
remote, and not configuring it later after stuff might already be stored
in the remote.
Went with =yes rather than =true for consistency with other parts of
git-annex. Changed docs accordingly.
This commit was supported by the NSF-funded DataLad project.
This will allow disabling exports for remotes that are not configured to
allow them. Also, exportSupported will be useful for the external
special remote to probe.
This commit was supported by the NSF-funded DataLad project
So it will be available later and elsewhere, even after GC.
I first though to use git update-index to do this, but feeding it a line
with a tree object seems to always cause it to generate a git subtree
merge. So, fell back to using the Git.Tree interface to maniupulate the
trees, and not involving the git-annex branch index file at all.
This commit was sponsored by Andreas Karlsson.
This avoids needing to deal with the complexity of partially transferred
files in the export. We'd not be able to resume uploading to such a file
anyway, so just avoid them.
The implementation in Remote.Directory is not completely ideal, because
it could leave the temp file hanging around in the export directory.
This only happens if it's killed with -9, or there's a power failure;
normally viaTmp cleans up after itself, even when interrupted. I could
not see a better way to do it though, since the export directory might
be the root of a filesystem.
Also some design thoughts on resuming, which depend on storeExport being
atomic.
This commit was sponsored by Fernando Jimenez on Partreon.
Make a pass over the whole exported tree, and upload anything that has
not yet reached the export. Update location log when exporting.
Note that the synthesized keys for non-annexed files are stored in the
location log too.
Some cases involving files in the tree with the same content are not
handled correctly yet.
This commit was sponsored by Boyd Stephen Smith Jr. on Patreon.
Rather than providing the key to export, provide the file.
When exporting a treeish that contains files that are not annexed,
this will let the content of those files also be exported.
There's still a Key in the interface; it will be used by the external
special remote protocol. A SHA1 key can be used when exporting
non-annexed files.
This commit was sponsored by Brock Spratlen on Patreon.
Implemented so far for the directory special remote.
Several remotes don't make sense to export to. Regular Git remotes,
obviously, do not. Bup remotes almost certianly do not, since bup would
need to be used to extract the export; same store for Ddar. Web and
Bittorrent are download-only. GCrypt is always encrypted so exporting to
it would be pointless. There's probably no point complicating the Hook
remotes with exporting at this point. External, S3, Glacier, WebDAV,
Rsync, and possibly Tahoe should be modified to support export.
Thought about trying to reuse the storeKey/retrieveKeyFile/removeKey
interface, rather than adding a new interface. But, it seemed better to
keep it separate, to avoid a complicated interface that sometimes
encrypts/chunks key/value storage and sometimes users non-key/value
storage. Any common parts can be factored out.
Note that storeExport is not atomic.
doc/design/exporting_trees_to_special_remotes.mdwn has some things in
the "resuming exports" section that bear on this decision. Basically,
I don't think, at this time, that an atomic storeExport would help with
resuming, because exports are not key/value storage, and we can't be
sure that a partially uploaded file is the same content we're currently
trying to export.
Also, note that ExportLocation will always use unix path separators.
This is important, because users may export from a mix of windows and
unix, and it avoids complicating the API with path conversions,
and ensures that in such a mix, they always use the same locations for
exports.
This commit was sponsored by Bruno BEAUFILS on Patreon.
