Re: tramp (2.6.1 HEAD/3ff676c2f98cb6c47fecb37f31a589a910dd3876); docker-container ssh multi-hop support

[Kristofer Hjelmtorp]

> From: Michael Albinus <michael.albinus@gmx.de>
> Subject: Re: tramp (2.6.1 
> HEAD/3ff676c2f98cb6c47fecb37f31a589a910dd3876);
>  docker-container ssh multi-hop support
> To: Gene Goykhman <gene@indigo1.com>
> Cc: tramp-devel@gnu.org,  Protesilaos Stavrou 
> <public@protesilaos.com>
> Date: Mon, 24 Jul 2023 09:45:53 +0200 (1 week, 9 hours, 10 
> minutes ago)
> Flags: seen, list
> Maildir: /mailbox/Inbox/TRAMP Dev
>
> Gene Goykhman <gene@indigo1.com> writes:
>
> > Hello and thank you for making TRAMP amazing!
>
> Hi Gene,

Hello, I saw this thread and wanted to jump in with some thoughts.

> > I don't know whether this is a bug or currently unsupported
> > functionality, but I am trying to get docker-container support 
> > through an
> > ssh connection and it is not working. docker-container works 
> > fine for
> > docker running on the local machine.
> >
> > However:
> >
> >   M-x find-file RET /ssh:root@remotehost|docker:
> >
> > Also suggests the SAME list of docker containers running on the 
> > local
> > host, rather than the (expected) list of containers on 
> > remotehost.
>
> Yes, this is a general weakness of Tramp, for all methods. It 
> doesn't
> complete user and host names for multi-hop names but the first
> hop. Perhaps I shall add something which doesn't offer 
> completion in
> this case.

A very simple change I tried when previously trying to get 
multihop completion working
with another backend was that if I changed the variable 
`tramp-compat-temporary-file-directory'
for the function `temporary-file-directory' in the completion 
functions (like `tramp-container--completion-function'), 
then at least we get completion when we are on the remote server. 
It doesn't give us completion for a multi-hop when 
we are starting in the local computer but if we first jump to the 
remote host and then try a multi-hop, we get completion 
for the container names.

Now their may reasons why we shouldn't call 
`temporary-file-directory' that I don't know about.


But for a more general solution; would it be possible to parse the 
whole tramp path while doing the completion and setting the 
`default-directory'
depending on where in the multi-hop path we are at the moment?
So when we are past "/ssh:user@host|" we start setting the 
default-directory to a tmp dir on "user@host".

Another issue that I found, which maybe is unavoidable, is that 
some of the completion functions in `tramp-container' requires 
that the container
program is installed on the local host, but sometimes I only have 
those programs installed on the remote host. Which stop the 
completion from working.

> > I tried ignoring the (incorrect) completion candidates and 
> > manually typing the name of the
> > running docker container on the remote host as follows:
> >
> >   M-x find-file RET 
> >   /ssh:root@remotehost|docker:remotecontainername
> >
> > But that opened a new, empty buffer in Fundamental mode and 
> > emitted the
> > error: "File not found and directory write-protected"
>
> This misses the trailing colon, you need
>
> M-x find-file RET 
> /ssh:root@remotehost|docker:remotecontainername:
>
> > Is using TRAMP to connect to docker containers running on a 
> > remote host
> > via ssh (i.e. multihop) supported? If so, could you point me to 
> > some information or
> > instructions?
>
> Yes, it is supported. I test it regularly with the regression 
> tests. If
> it still doesn't work for you, pls set tramp-verbose to 6 and 
> rerun the
> test. Show the resulting Tramp debug buffer.
>
> > Thank you!
>
> Best regards, Michael.


--
Best Regards
Kristofer