This is a summary todo covering several subprojects, which would extend
git-annex to be able to use proxies which sit in front of a cluster of
repositories.

1. [[design/passthrough_proxy]]
2. [[design/p2p_protocol_over_http]]
3. [[design/balanced_preferred_content]]
4. [[todo/track_free_space_in_repos_via_git-annex_branch]]
5. [[todo/proving_preferred_content_behavior]]

Joey has received funding to work on this.
Planned schedule of work:

* June: git-annex proxies and clusters
* July, part 1: git-annex proxy support for exporttree
* July, part 2: p2p protocol over http
* August: balanced preferred content
* September: streaming through proxy to special remotes (especially S3)
* October: proving behavior of balanced preferred content with proxies

[[!tag projects/openneuro]]

# work notes

In development on the `proxy` branch.

For June's work on [[design/passthrough_proxy]], remaining todos:

* Since proxying to special remotes is not supported yet, and won't be for
  the first release, make it fail in a reasonable way.

- or -

* Proxying for special remotes.
  Including encryption and chunking. See design for issues.

# items deferred until later for [[design/passthrough_proxy]]

* Indirect uploads when proxying for special remote
  (to be considered). See design.

* Getting a key from a cluster currently picks from amoung
  the lowest cost remotes at random. This could be smarter,
  eg prefer to avoid using remotes that are doing other transfers at the
  same time.

* The cost of a proxied node that is accessed via an intermediate gateway
  is currently the same as a node accessed via the cluster gateway.
  To fix this, there needs to be some way to tell how many hops through
  gateways it takes to get to a node. Currently the only way is to
  guess based on number of dashes in the node name, which is not satisfying.

  Even counting hops is not very satisfying, one cluster gateway could
  be much more expensive to traverse than another one.

  If seriously tackling this, it might be worth making enough information
  available to use spanning tree protocol for routing inside clusters.

* Optimise proxy speed. See design for ideas.

* Use `sendfile()` to avoid data copying overhead when
  `receiveBytes` is being fed right into `sendBytes`.
  Library to use:
  <https://hackage.haskell.org/package/hsyscall-0.4/docs/System-Syscall.html>

* Support using a proxy when its url is a P2P address.
  (Eg tor-annex remotes.)

# completed items for June's work on [[design/passthrough_proxy]]:

* UUID discovery via git-annex branch. Add a log file listing UUIDs
  accessible via proxy UUIDs. It also will contain the names
  of the remotes that the proxy is a proxy for, 
  from the perspective of the proxy. (done)

* Add `git-annex updateproxy` command (done)

* Remote instantiation for proxies. (done)

* Implement git-annex-shell proxying to git remotes. (done)

* Proxy should update location tracking information for proxied remotes,
  so it is available to other users who sync with it. (done)

* Implement `git-annex initcluster` and `git-annex updatecluster` commands (done)

* Implement cluster UUID insertation on location log load, and removal
  on location log store. (done)

* Omit cluster UUIDs when constructing drop proofs, since lockcontent will
  always fail on a cluster. (done)

* Don't count cluster UUID as a copy in numcopies checking etc. (done)

* Tab complete proxied remotes and clusters in eg --from option. (done)

* Getting a key from a cluster should proxy from one of the nodes that has
  it. (done)

* Implement upload with fanout to multiple cluster nodes and reporting back
  additional UUIDs over P2P protocol. (done)

* Implement cluster drops, trying to remove from all nodes, and returning
  which UUIDs it was dropped from. (done)

* `git-annex testremote` works against proxied remote and cluster. (done)

* Avoid `git-annex sync --content` etc from operating on cluster nodes by
  default since syncing with a cluster implicitly syncs with its nodes. (done)

* On upload to cluster, send to nodes where its preferred content, and not
  to other nodes. (done)

* Support annex.jobs for clusters. (done)

* Add `git-annex extendcluster` command and extend `git-annex updatecluster` 
  to support clusters with multiple gateways. (done)

* Support proxying for a remote that is proxied by another gateway of
  a cluster. (done)

* Support distributed clusters: Make a proxy for a cluster repeat
  protocol messages on to any remotes that have the same UUID as
  the cluster. Needs extension to P2P protocol to avoid cycles.
  (done)

* Proxied cluster nodes should have slightly higher cost than the cluster
  gateway. (done)