Tmux integration sometimes fails to start when connecting to remote server

Hi!

I'm using tmux integration mode to connect to remote server running tmux. Sometimes it refuses to connect with the following message: Reason: %begin with empty command queue. I'm able to reproduce it with this steps:

1. Close all tabs, quit iTerm2 and launch it again - it now has a single tab.
2. Try to connect to remote server with the command ssh foo -t "tmux -CC attach -t foo || tmux -CC new -s foo". (tmux session was not started before)
3. iTerm creates a new window for the session (according to my settings) with a single tab.
4. Type Ctrl+D to quit the remote shell. It will end remote tmux session and iTerm will disconnect.
5. Try to connect again with the same command.
6. You'll get the alert with Reason: %begin with empty command queue.
7. Subsequent attempts to connect may fail at random.

$ ssh imp -t "tmux -CC attach -t imp || tmux -CC new -s imp" 
** tmux mode started **

Command Menu
----------------------------
esc    Detach cleanly.
  X    Force-quit tmux mode.
  L    Toggle logging.
  C    Run tmux command.
Detached
Connection to imp closed.
$ ssh imp -t "tmux -CC attach -t imp || tmux -CC new -s imp" 
** tmux mode started **

Command Menu
----------------------------
esc    Detach cleanly.
  X    Force-quit tmux mode.
  L    Toggle logging.
  C    Run tmux command.
Detached
show-window-options -g aggressive-resize
refresh-client -C 160,75; list-windows -F "#{window_id} #{window_layout}"
** tmux mode started **

Command Menu
----------------------------
esc    Detach cleanly.
  X    Force-quit tmux mode.
  L    Toggle logging.
  C    Run tmux command.
Detached
%begin 1451118518 14 1
%end 1451118518 14 1
%exit
Connection to imp closed.

• iTerm2 version: Build 2.1.4
• remote tmux version: 2.1
• OS version: 10.9.5
• ~/Library/Preferences/com.googlecode.iterm2.plist
• Attach a debuglog.txt.gz

It seems there was no existing session to attach to. Unfortunately the error message gets buried because the hooks aren't there to handle responses to commands sent on the command line (like tmux attach).

Try tmux new-session -A instead.

Hi, George!

Yes, there is no session, but that's why there is the second part of the ssh command (tmux -CC attach -t imp || tmux -CC new -s imp). I think, that the problem lies in the attach in integration mode producing commands as well, which confuses iTerm.

$ ssh imp -t -C "tmux -CC attach -t foo || tmux -CC new -s foo"
1000p%begin 1451922733 1 0
can't find session foo
%error 1451922733 1 0
%exit
1000p%begin 1451922733 1 0
%end 1451922733 1 0
%window-add @12
%sessions-changed
%session-changed $11 foo
%layout-change @12 5961,80x24,0,0,12
%output %12 [imp ~]$

So the question is - should tmux -CC attach produce commands if there is no session to attach?

Meanwhile, new-session -A worked like a charm. Thank you, George!

There's some special handling for initial launch which is a bit fragile. The problem is the use of new. The following works (at least for me, in the beta version):

ssh -t example.com "tmux -CC attach -t foo || tmux -CC -s foo"

Milestone changed to Feature Complete 3.1

@gnachman In my case, ssh -t example.com "tmux -CC attach -t foo || tmux -CC -s foo" fails already on the tmux side of things with tmux: unknown option -- s, presumably because tmux fails to imply the new in the fallback command. If I put it there explicitly, I get the same problem as described in the OP (with the message window from iTerm2), though in the meantime tmux clearly starts on the remote server because if I try to connect a second time, it succeeds and everything works peachy.

A better workaround in my case seems to be to put new in my barebones .tmux.conf and just run ssh -t example.com "tmux -CC attach". If no session is found, attach falls back to initializing a session using .tmux.conf if it finds one there (which it does thanks to the new).

Let me know if I can be of any help in debugging this!

I don't know what I was thinking but that was obviously wrong! This command should do what you want:

ssh -t example.com "tmux -CC new-session -A -s foo"

Yes, thank you, that works perfectly and it's very elegant! It also makes perfect sense, after reading the relevant section of the man page :)

By the way, I'm falling in love with iTerm's tmux integration! (Especially viewing images from the terminal is handy, no more rsync / scp / cp -t ~/public_html just to check which of my assets is which.) Let me just find that donate button...

Cheers and thanks a lot once again for everything!

Status changed to closed