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This is to avoid inserting a cluster uuid into the location log when only dead nodes in the cluster contain the content of a key. One reason why this is necessary is Remote.keyLocations, which excludes dead repositories from the list. But there are probably many more. Implementing this was challenging, because Logs.Location importing Logs.Cluster which imports Logs.Trust which imports Remote.List resulted in an import cycle through several other modules. Resorted to making Logs.Location not import Logs.Cluster, and instead it assumes that Annex.clusters gets populated when necessary before it's called. That's done in Annex.Startup, which is run by the git-annex command (but not other commands) at early startup in initialized repos. Or, is run after initialization. Note that is Remote.Git, it is unable to import Annex.Startup, because Remote.Git importing Logs.Cluster leads the the same import cycle. So ensureInitialized is not passed annexStartup in there. Other commands, like git-annex-shell currently don't run annexStartup either. So there are cases where Logs.Location will not see clusters. So it won't add any cluster UUIDs when loading the log. That's ok, the only reason to do that is to make display of where objects are located include clusters, and to make commands like git-annex get --from treat keys as being located in a cluster. git-annex-shell certainly does not do anything like that, and I'm pretty sure Remote.Git (and callers to Remote.Git.onLocalRepo) don't either.
94 lines
3.3 KiB
Markdown
94 lines
3.3 KiB
Markdown
This is a summary todo covering several subprojects, which would extend
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git-annex to be able to use proxies which sit in front of a cluster of
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repositories.
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1. [[design/passthrough_proxy]]
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2. [[design/p2p_protocol_over_http]]
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3. [[design/balanced_preferred_content]]
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4. [[todo/track_free_space_in_repos_via_git-annex_branch]]
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5. [[todo/proving_preferred_content_behavior]]
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Joey has received funding to work on this.
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Planned schedule of work:
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* June: git-annex proxy
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* July, part 1: git-annex proxy support for exporttree
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* July, part 2: p2p protocol over http
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* August: balanced preferred content
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* September: streaming through proxy to special remotes (especially S3)
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* October: proving behavior of balanced preferred content with proxies
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[[!tag projects/openneuro]]
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# work notes
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In development on the `proxy` branch.
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For June's work on [[design/passthrough_proxy]], implementation plan:
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* UUID discovery via git-annex branch. Add a log file listing UUIDs
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accessible via proxy UUIDs. It also will contain the names
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of the remotes that the proxy is a proxy for,
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from the perspective of the proxy. (done)
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* Add `git-annex updateproxy` command (done)
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* Remote instantiation for proxies. (done)
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* Implement git-annex-shell proxying to git remotes. (done)
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* Proxy should update location tracking information for proxied remotes,
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so it is available to other users who sync with it. (done)
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* Implement `git-annex updatecluster` command (done)
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* Implement cluster UUID insertation on location log load, and removal
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on location log store. (done)
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* Omit cluster UUIDs when constructing drop proofs, since lockcontent will
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always fail on a cluster. (done)
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* Don't count cluster UUID as a copy. (Including in `whereis` display.)
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Work in progress. fromNumCopies is sometimes used to get a
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number that is compared with a list of UUIDs. And limitCopies doesn't
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use numcopies machinery
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* Basic proxying to special remote support (non-streaming).
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* Consider getting instantiated remotes into git remote list.
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See design.
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* Implement upload with fanout and reporting back additional UUIDs over P2P
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protocol.
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* Getting a key from a cluster should proxy from one of the nodes that has
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it, or from the proxy repository itself if it has the key.
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* On upload to a cluster, as well as fanout to nodes, if the key is
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preferred content of the proxy repository, store it there.
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(But not when preferred content is not configured.)
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* Implement cluster drops, trying to remove from all nodes, and returning
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which UUIDs it was dropped from.
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* Support proxies-of-proxies better, eg foo-bar-baz.
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Currently, it does work, but have to run `git-annex updateproxy`
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on foo in order for it to notice the bar-baz proxied remote exists,
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and record it as foo-bar-baz. Make it skip recording proxies of
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proxies like that, and instead automatically generate those from the log.
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(With cycle prevention there of course.)
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* Cycle prevention including cluster-in-cluster cycles. See design.
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* Optimise proxy speed. See design for ideas.
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* Use `sendfile()` to avoid data copying overhead when
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`receiveBytes` is being fed right into `sendBytes`.
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* Encryption and chunking. See design for issues.
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* Indirect uploads (to be considered). See design.
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* Support using a proxy when its url is a P2P address.
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(Eg tor-annex remotes.)
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