better design

Avoids possible repeated password prompts, at the cost of a small bit of
locking complication.

1 files changed, 9 insertions, 15 deletions

diff --git a/doc/todo/wishlist:_Prevent_repeated_password_prompts_for_one_command.mdwn b/doc/todo/wishlist:_Prevent_repeated_password_prompts_for_one_command.mdwn
index e5b5e3c5c..a047370ac 100644
--- a/doc/todo/wishlist:_Prevent_repeated_password_prompts_for_one_command.mdwn
+++ b/doc/todo/wishlist:_Prevent_repeated_password_prompts_for_one_command.mdwn
@@ -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`