João Távora <joaotavora@gmail.com> writes:

> So maybe one should disable it by default.  How does one disable it? I
> have trouble understanding from tramp-use-ssh-controlmaster-options and
> tramp-ssh-controlmaster-options.

In the meantime I have finally, with great Docker-relearning hardship,
setup a reproduction environment.  You'll see it follows exactly
Thomas's reproduction recipe almost until the end.  It sets up a server
on port 2022 

I attach the dockerfile.

$ docker build -t sshubuntu .
$ docker run -d -p 2022:22 sshubuntu
$ /path/to/emacs -Q /ssh:sshuser@localhost#2022:/home/sshuser/yacy_search_server/source/net/yacy/yacy.java -f eglot

Now the odd bit.  Sometimes this works, sometimes it doesn't!!!
Sometimes it finds '~/bin/jtdls' in the remote's PATH and sometimes it
doesn't!  I have no idea why.  Maybe someone can help me debug: how is
PATH to work?  In the server I can see that on simple ssh login,
~/bin/jdtls _is_ found.

Anyway, when I _do_ manage to get it to find sshuser's '~/bin/jtdls':

* I do experience the hang regularly, but not always at the same point
  in time.

* I don't know how to obtain the pretty Backtrace that you Michael got.
  Michael how do you get that??  Maybe you're using some tramp flag,
  because debug-on-error and debug-on-quit don't work.

* If I set 

    (setq tramp-ssh-controlmaster-options nil
        tramp-use-ssh-controlmaster-options nil)

  I _no longer_ experience the hang.  This is after visiting 5 or 6
  files, trying some completion, M-. xref-find-definitions, etc.

Michael can you confirm that these are per-buffer values?  Would it
make sense for Eglot to set them like so in its minor mode hook?

João