52 lines
2.2 KiB
Text
52 lines
2.2 KiB
Text
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[[!comment format=mdwn
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username="joey"
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subject="""comment 4"""
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date="2017-07-10T17:30:23Z"
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content="""
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Yoh suggested storing a treeish associated with the export to a special
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remote. Pointed out that the diff from that treeish to the next one could
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be used to update the export.
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(That does seem very close to [[todo/dumb, unsafe, human-readable_backend]].)
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Would need to somehow deal with partial uploads. There are two ways
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an upload can be partial:
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* Some of the files in the treeish have been uploaded; others have not.
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* A file has been partially uploaded.
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These two cases need to be disentangled somehow in order to handle
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them. It could use the location log, so once a key gets uploaded
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to the special remote, its content is marked present. However, using the
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location log does not seem sufficient to handle all cases (eg two files
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swapping names between two treeishes, where one of the files has been
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uploaded only partially to the special remote).
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It seems promosing to keep track of two separate treeishes:
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1. The treeish that is the current goal to have exported to the special
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remote.
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2. The treeish for the current state of the special remote. Note that
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after even an interrupted transfer, this treeish needs to be updated to
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contain the current state of the special remote, which would mean
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constructing a new treeish. (Perhaps a per-remote index file could be
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used.)
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Having these two treeishes allows:
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* Detecting renames of exported files, which some special remotes can do
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more efficiently.
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* Determining the key that a given file on the special remote is
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storing the content of.
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* Resuming an interrupted export, without re-uploading all the files.
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* Detecting a partially uploaded file, because the current state treeish
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for the remote should not contain that file.
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* Knowing what key was in the process of being sent to a partially uploaded
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file, and so resuming that upload. Look at the goal treeish and see what
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key it has for the file; as long as the goal treeish is the same goal
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that was used for the interrupted export, that's the key. (This needs a
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way to track if the goal has changed.)
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* Optionally, making `git annex sync` and the assistant upload as needed
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to satisfy goal treeishes for special remotes.
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"""]]
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