design

1 files changed, 31 insertions, 0 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 808b8496f..e5b5e3c5c 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
@@ -16,3 +16,34 @@ Simple, when performing various git annex command over ssh, in particular a mult
 >> 
 >> Complicated slightly by not doing this if the user has already set up
 >> more broad ssh connection caching. --[[Joey]]
+
+---
+
+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.
+* 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`
+     (Will exit nonzero if ssh is not running on that socket.)
+  3. And then remove the socket.
+* 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`