69 lines
3.1 KiB
Markdown
69 lines
3.1 KiB
Markdown
git annex sync supports git remote groups, that should be expanded to all
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commands supporting --to and --from. And since there will be a [Remote]
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list, could also support --to foo --to bar etc.
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--[[Joey]]
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Started working on this in multifromto branch.
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Problem: Command.Move uses onlyActionOn, so only allows one remote to
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process a key at a time. Seems that onlyActionOn needs to be expanded to
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include the remote.
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Problem: The concurrency is not right yet. For example,
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`git-annex copy --to foo --to bar -J2` will start actions copying a
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file to both remotes. Assume the copy to bar finishes first.
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Then it will start an action copying the next file to foo, despite a
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copy to foo already running.
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To fix this, it would help to look at Annex.activeremotes when starting the
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next action. If foo is busy, start the action on bar instead. It would
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be possible to build up a queue of actions that have not yet been started on
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a remote. That risks using a lot of memory if one remote is very slow.
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The queue would need to be capped at some amount, and when full,
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delay until the laggard remotes catches up.
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Bonus: git annex sync --content -J2 already works, but it has the same
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problem described above and ought to be able to be fixed the same way.
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Also worth noting that with --auto and -J, git-annex may make more transfers
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than preferred content settings demand, because it will start several
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transfers to different remotes at once. If only one copy is needed
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amoung all the remotes, it won't notice and a copy will be sent to all
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remotes. I think this is something the user can understand though?
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----
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Looking at commands that support --to and --from and what each should do,
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there is a lot of diversity.
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git annex move --to of course removes the local copy. So if moving to
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multiple remotes it would need to delay that removal until it's sent to all
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of them. And it really only ought to try to remove the local copy once
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at the end, not once per remote moved to.
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git annex move --from ought to spread the load amoung remotes with -Jn,
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and once a file is downloaded, it needs to try to remove it from all the
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remotes.
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git annex mirror --from mirrors one remote; mirroring from
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multiple remotes does not really make any sense. mirror --to multiple
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could be done.
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git annex unused --from seems unlikely to make sense with multiple remotes,
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since it would result in a list of keys distributed amoung them, and what
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would be done with that? Perhaps a git annex drop --from multiple remotes,
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but that would be innefficient. A shell script looping over remotes makes
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more sense if the user wants to drop unused from multiple remotes.
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git annex get/fsck/copy/export/transferkey/drop/dropunused all make sense to
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support multiple remotes. But with -Jn the operations that get files behave
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differently than the operations that drop files. The gets want to balance
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load amoung the remotes, while the drops and uploads need to run each
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action over each remote.
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Seems two runners are needed with different concurrency behavior, one that
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balances the load amoung remotes, and one that runs the same action against
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multiple remotes concurrently.
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[[!tag needsthought]]
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