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better design

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Avoids possible repeated password prompts, at the cost of a small bit of
locking complication.
This commit is contained in:
Joey Hess 2012-01-19 21:15:13 -04:00
parent 3783ccf252
commit e96726caa3
1 changed files with 9 additions and 15 deletions
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24
doc/todo/wishlist:_Prevent_repeated_password_prompts_for_one_command.mdwn
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@ -22,28 +22,22 @@ Simple, when performing various git annex command over ssh, in particular a mult
Slightly more elaborate design for using ssh connection caching:
* Per-uuid ssh socket in `.git/annex/ssh/user@host.socket`
* Can be shared amoung concurrent git-annex processes.
* Can be shared amoung concurrent git-annex processes as well as ssh
invocations inside the current git-annex.
* Also a lock file, `.git/annex/ssh/user@host.lock`.
Open and take shared lock before running ssh; store lock in lock pool.
(Not locking socket directly, because ssh might want to.)
* Run ssh like: `ssh -S .git/annex/ssh/user@host.socket -o ControlMaster=auto -o ControlPersist=yes user@host`
* At shutdown, enumerate all existing sockets, and on each:
1. Rename to .old (prevents various races)
2. `ssh -q -S .git/annex/ssh/user@host.old -o ControlMaster=auto -o ControlPersist=yes -O stop user@host`
1. Drop any shared lock.
2. Attempt to take an exclusive lock (non-blocking).
3. `ssh -q -S .git/annex/ssh/user@host.socket -o ControlMaster=auto -o ControlPersist=yes -O stop user@host`
(Will exit nonzero if ssh is not running on that socket.)
3. And then remove the socket.
4. And then remove the socket and the lock file.
* Do same *at startup*. Why? In case an old git-annex was interrupted
and left behind a ssh. May have moved to a different network
in the meantime, etc, and be stalled waiting for a response from the
network, or talking to the wrong interface or something.
(Ie, the reason why I don't use ssh connection caching by default.)
* This would stop ssh's used by a concurrently running git-annex,
but only after they finish servicing their current connection.
Could use locks to detect if another git-annex is using a ssh
socket, but concurrent git-annex is rare enough, and the impact small
enough (next ssh it runs needs to do a full connect), that
the locks are probably not justified. Could be added later if needed tho.
* Could also set ControlPersist to something like "1h", in order to
auto-terminate leftover ssh's when git-annex is ctrl-c'd or somehow
exits. When transferring big enough files that the next ssh doesn't
happen for an hour, the overhead of that ssh needing to reconnect is
not significant.
* User should be able to override this, to use their own preferred
connection caching setup. `annex.sshcaching=false`