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on cycles

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Joey Hess 2024-06-12 13:52:17 -04:00
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19
doc/design/passthrough_proxy.mdwn
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@ -282,6 +282,23 @@ in front of the proxy.
## cycles
A repo can advertise that it proxies for a repo which has the same uuid as
itself. Or there can be a larger cycle involving a proxy that proxies to a
proxy, etc.
Since the proxied repo uuid is communicated to git-annex-shell via
--uuid, a repo that advertises proxying for itself will be connected to
with its own uuid. No proxying is done in this case. Same happens with a
larger cycle.
Instantiating remotes needs to identity cycles and break them. Otherwise
it would construct an infinite number of proxied remotes with names
like "foo-foo-foo-foo-..." or "foo-bar-foo-bar-..."
Once `git-annex copy --to proxy` is implemented, and the proxy decides
where to send content that is being sent directly to it, cycles will
become an issue with that as well.
What if repo A is a proxy and has repo B as a remote. Meanwhile, repo B is
a proxy and has repo A as a remote?
@ -295,7 +312,7 @@ remote that is not part of a cycle, they could deposit the upload there and
the upload still succeed. Otherwise the upload would fail, which is
probably the best that can be done with such a broken configuration.
So, it seems like proxies will need to take transfer locks for uploads,
So, it seems like proxies would need to take transfer locks for uploads,
even though the content is being proxied to elsewhere.
Dropping could have similar cycles with content presence locking, which

7
doc/todo/git-annex_proxies.mdwn
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@ -44,6 +44,13 @@ For June's work on [[design/passthrough_proxy]], implementation plan:
* Consider getting instantiated remotes into git remote list.
See design.
* Support proxies-of-proxies better, eg foo-bar-baz.
Currently, it does work, but have to run `git-annex updateproxy`
on foo in order for it to notice the bar-baz proxied remote exists,
and record it as foo-bar-baz. Make it skip recording proxies of
proxies like that, and instead automatically generate those from the log.
(With cycle prevention there of course.)
* Cycle prevention. See design.
* Make `git-annex copy --from $proxy` pick a node that contains each