83 lines
3.1 KiB
Markdown
83 lines
3.1 KiB
Markdown
Some remotes are too small to sync everything to them.
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The case of a small remote on a gadget that the user interacts with,
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such as a phone, where they may want to request it get content
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it doesn't currently have, is covered by the [[partial_content]] page.
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But often the remote is just a removable drive or a cloud remote,
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that has a limited size. This page is about making the assistant do
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something smart with such remotes.
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## specifying what data belongs on a remote
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Imagine a per-remote `annex-accept` setting, that matches things that
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should be stored on the remote.
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For example, a MP3 player might use:
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`smallerthan(10mb) and filename(*.mp3) and (not filename(junk/*))`
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Adding that as a filter to files sent to a remote should be
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straightforward.
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A USB drive that is carried between three laptops and used to sync data
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between them might use: `not (in=laptop1 and in=laptop2 and in=laptop3)`
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In this case, transferring data from the usb repo should
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check if `annex-accept` then rejects the data, and if so, drop it
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from the repo. So once all three laptops have the data, it is
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pruned from the transfer drive.
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It may make sense to have annex-accept info also be stored in the git-annex
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branch, for settings that should apply to a repo globally. Does it make
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sense to have local configuration too?
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## repo groups
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Seems like git-annex needs a way to know the groups of repos. Some
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groups:
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* enduser: The user interacts with this repo directly.
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* archival: This repo accumulates stuff, and once it's in enough archives,
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it tends to get removed from other places.
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* transfer: This repo is used to transfer data between enduser repos,
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it does not hold data for long periods of time, and tends to have a
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limited size.
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Add a group.log that can assign repos to these or other groups. **done**
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Some examples of using groups:
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* Want to remove content from a repo, if it's not an archival repo,
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and the content has reached at least one archival repo:
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`(not group=archival) and (not copies=archival:1)`
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That would make send to configure on all repos, or even set
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a global `annex.accept` to it. **done**
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* Make a cloud repo only hold data until all known clients have a copy:
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`not inall(enduser)`
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## configuration
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The above is all well and good for those who enjoy boolean algebra, but
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how to configure these sorts of expressions in the webapp?
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## the state change problem
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Imagine that a trusted repo has setting like `not copies=trusted:2`
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This means that `git annex get --auto` should get files not in 2 trusted
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repos. But once it has, the file is in 3 trusted repos, and so `git annex
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drop --auto` should drop it again!
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How to fix? Can it even be fixed? Maybe care has to be taken when
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writing expressions, to avoid this problem. One that avoids it:
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`not (copies=trusted:2 or (in=here and trusted=here and copies=trusted:3))`
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Or, expressions could be automatically rewritten to avoid the problem.
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Or, perhaps simulation could be used to detect the problem. Before
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dropping, check the expression. Then simulate that the drop has happened.
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Does the expression now make it want to add it? Then don't drop it!
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How to implement this simulation?
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