emacs tramp over an unreliable connection

Question

I want to run R on a remote box under a local Emacs (I do not want to run Emacs on the remote box).

I can run R on a remote host using TRAMP:

(let ((default-directory "/user@remote:~"))
  (R))

and everything works fine except that when the connection to remote is lost, R dies. This is no good because this means that I have to re-load all the data into R after restarting it, which takes time.

Is it possible to tell TRAMP to use a persistent terminal? (GNU Screen or tmux or Mosh or dtach)

See also emacs-devel thread tramp:sshx:(screen|tmux).

Phio

Answer 1

Here is how to use ESS with R running in a remote screen session:

• ssh to the remote host (outside of emacs)

• start screen session

• detach it

• open shell in emacs (M-x shell)

• ssh to the remote host again in the emacs shell

• resume the screen session (screen -r)

• start R

• finally attach ESS to the R process using M-x ess-remote in the shell buffer where you started R

There are more details, screenshots, and keybindings in this post http://blog.nguyenvq.com/2010/07/11/using-r-ess-remote-with-screen-in-emacs/

Capsular

ESS developers seem to consider ess-remote to be obsolete. – Phio

Well, the function itself is rather simple, all it does is sets a few variables and initializes inferior-ess mode for the buffer plus some language-specific customizations. I use ess-remote a lot to run remote R and SAS processes and have not had any problems with the function. You can also use it with R launched ssh.el – Capsular

@Phio As ESS developer I can assure that ess-remote is maintaned and is improving. I am looking into screen integration with ess and tramp/ess-remote. Any ideas suggestions are welcome. – Miner

Um, this doesn't work. Emacs shell sets your TERM to dumb. When you ssh to the remote host, you find that screen doesn't support your terminal setting. "Clear screen capability required." – Alamein

Try setting TERM=xterm after you launch shell in emacs, then ssh, etc. – Capsular

You could always use the Emacs terminal (M-x ansi-term) to run your shell, instead of M-x shell. If all you want to do locally is ssh to the remote host, you could even run ssh directly in the terminal, instead of a shell. In some cases you'd also want to make eterm-color a recognised terminal type on the remote host. – Rema

Following all these steps worked but the connection is super laggy used from org-mode (compared to launching the R session via org-mode/ess)? Any suggestions? – Masked

Answer 2

Here is an alternative approach using dtach:

(defvar R-remote-host "remote-server")
(defvar R-remote-session "R")
(defvar R-remote-directory "~")
(defun R-remote (&optional remote-host session directory)
  "Connect to the remote-host's dtach session running R."
  (interactive (list
                (read-from-minibuffer "R remote host: " R-remote-host)
                (read-from-minibuffer "R remote session: " R-remote-session)
                (read-from-minibuffer "R remote directory: " R-remote-directory)))
  (pop-to-buffer (make-comint (concat "remote-" session)
                              "ssh" nil "-t" "-t" remote-host
                              "cd" directory ";"
                              "dtach" "-A" (concat ".dtach-" session)
                              "-z" "-E" "-r" "none"
                              inferior-R-program-name "--no-readline"
                              inferior-R-args))
  (ess-remote (process-name (get-buffer-process (current-buffer))) "R")
  (setq comint-process-echoes t))

Call M-x R-remote RET RET RET RET.

It works for me.

PS. The answer to the problem (as opposed to the question as asked) is to use ein with Jupyter.

Phio

Thanks for your code. Right now when starting a remote process, the process starts in the home directory. I tried to modify your code open R remotely in a specific directory but had some problem achieving this. Do you have any way of choosing the directory where the process should start? – Scalise

Ok I got it just adding the line "cd ~/Documents/R;" after remote host does the job. Many thanks again for your code it saved me a lot of trouble. – Scalise

@DJJ: I added R-remote-directory, thanks for the suggestion. – Phio