5b332a87be
Dropping from a cluster drops from every node of the cluster. Including nodes that the cluster does not think have the content. This is different from GET and CHECKPRESENT, which do trust the cluster's location log. The difference is that removing from a cluster should make 100% the content is gone from every node. So doing extra work is ok. Compare with CHECKPRESENT where checking every node could make it very expensive, and the worst that can happen in a false negative is extra work being done. Extended the P2P protocol with FAILURE-PLUS to handle the case where a drop from one node succeeds, but a drop from another node fails. In that case the entire cluster drop has failed. Note that SUCCESS-PLUS is returned when dropping from a proxied remote that is not a cluster, when the protocol version supports it. This is because P2P.Proxy does not know when it's proxying for a single node cluster vs for a remote that is not a cluster.
110 lines
4 KiB
Markdown
110 lines
4 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. (done)
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* Tab complete proxied remotes and clusters in eg --from option. (done)
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* Getting a key from a cluster should proxy from one of the nodes that has
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it. (done)
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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. (done)
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* Getting a key from a cluster currently always selects the lowest cost
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remote, and always the same remote if cost is the same. Should
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round-robin amoung remotes, and prefer to avoid using remotes that
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other git-annex processes are currently using.
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* Implement upload with fanout and reporting back additional UUIDs over P2P
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protocol. (done, but need to check for fencepost errors on resume of
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incomplete upload with remotes at different points)
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* On upload to cluster, send to nodes where it's preferred content, and not
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to other nodes.
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* Problem: `move --from cluster` in "does this make it worse"
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check may fail to realize that dropping from multiple nodes does in fact
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make it worse.
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* Bug: When a cluster has one node, copying a file to it does not update
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location log to say the content is present on it. It's returning SUCCESS
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rather than SUCCESS-PLUS.
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* Support annex.jobs for clusters.
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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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And on download from a cluster, if the proxy repository has the content,
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get it from there to avoid the overhead of proxying to a node.
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* Basic proxying to special remote support (non-streaming).
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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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