Vscode-remote-release: Stuck when connecting remote server using Remote Development while remote server is reachable in ssh (random nodes assigned)

[SaltedFishLZ]

• VSCode Version: 1.34.20-insider
• OS Version: Local Client - Ubuntu 16.04, Remote Server - Ubuntu 16.04

I am using a group server and when I try to connect it using the new Remote Development extension, the SSH tunnel process stalls. But I can use normal SSH to connect to the server.

The terminal outputs are as follows:

> bash: cannot set terminal process group (21617): Inappropriate ioctl for device
> bash: no job control in this shell
> Found existing installation...
> Found running server...
>  
> *
> * Reminder: You may only use this software with Visual Studio family products,
> * as described in the license (https://go.microsoft.com/fwlink/?linkid=2077057)
> *
>  
> 8ab17bf7-eebb-479a-a4d8-c0813ff9ec5c==46161==
"install" terminal command done
Received install output: 8ab17bf7-eebb-479a-a4d8-c0813ff9ec5c==46161==
Server is listening on port 46161
Spawning tunnel with: ssh  a18 -L localhost:42233:localhost:46161 "echo -e 'Connected to SSH Host - Please do not close this terminal' && sleep infinity"
Spawned SSH tunnel between local port 42233 and remote port 46161
Waiting for ssh tunnel to be ready
Tunneling remote port 46161 to local port 42233
Resolving "ssh-remote+a18" to "localhost:42233", attempt: 1
> channel 3: open failed: connect failed: Connection refused
> channel 4: open failed: connect failed: Connection refused
> channel 5: open failed: connect failed: Connection refused
> Connected to SSH Host - Please do not close this terminal

Does this issue occur when all extensions are disabled?: Yes

[roblourens]

the SSH tunnel process stalls

Can you explain what the problem is exactly? The log doesn't necessarily show an issue (Connection refused may or may not be an issue)

[SaltedFishLZ]

The problem is that I cannot create a new bash session or open any file in the remote group server in my university. In detail, when I tried to create a new bash session or open any file on the group server, VS Code has no response.
So I suspect that the SSH connection cannot be established correctly (I am not sure because the terminal tells me VS Code has connected to SSH Host).

[Update]

When I tried it on a Google Cloud server, it works. So there might be some problems on the university server. However, I cannot see any error information from the Remote Development extension. I don't know what to do.

[safelix]

Hi there, I experienced the same behavior as @SaltedFishLZ when trying to access an HPC cluster.

As the log suggests, the connection seems to be established. However, there is no response when I try to open Folder/Files. When I start a new terminal, it will open a new terminal without any contents.

I tried to investigate a little more on this by examining and debugging parts of %TEMP%\vscode-linux-multi-line-command-myHost.sh. After a while, I figured that the $PORT numbers did not always match:

> VSCode Output: Remote - SSH
...
Received install output: ababba7d-6b8f-447b-816b-0ddc7762d999==$PORT==
...

> cat "$HOME/.vscode-remote/.$COMMIT_ID.log" | grep -E 'Extension host agent listening on [0-9]+' | grep -v grep | grep -o -E '[0-9]+'
$PORT

> lsof -i
COMMAND   PID    USER   FD   TYPE   DEVICE SIZE/OFF NODE NAME
node    19279 user 13u  IPv6 38349751      0t0  TCP localhost:$PORT->localhost:$client_PORT (ESTABLISHED)

I then realized that the cluster, obviously, does some kind of load-balancing. By using ssh [email protected] there is no guarantee that I repeatedly connect to a specific node.

During the connection setup, the extension uses multiple ssh connections to the host, assuming that the domain is always resolved to the same machine. I am able to successfully start the server-script and successfully establish an ssh-tunnel but since the assumption does not hold, the local client doesn't receive any response.

I was able to circumvent the load-balancing, by accessing a specific node with ssh [email protected]. However, it would be nice if the server initialization and tunnel-establishing could be done in one step. But this is a question of what kind of systems you want to support. Also, a little bit more documentation and possibilities to modify the existing script would have saved me quite some time ;)

Thanks for this great extension, it makes my life much easier!

TL;DR
The extension assumes that a domain is always resolved to the same machine, which is not the case with clusters. Solution might be to access nodes directly.

[roblourens]

That's really interesting! I think your analysis is correct and would bet that @SaltedFishLZ is seeing the same thing.

I would like to get down to opening just one ssh connection but it's tricky. Another workaround for you might be using the "ControlMaster" feature, https://code.visualstudio.com/docs/remote/troubleshooting#_enabling-alternate-ssh-authentication-methods

[safelix]

Yes, I would expect the "ControlMaster" feature to be a much cleaner workaround. Unfortunately, I'm using OpenSSH on Windows where this features is not supported (yet). https://github.com/PowerShell/Win32-OpenSSH/issues/1328

Yes, doing it in one ssh connection without Control Master seems to be very tricky. This is what I found on the topic, but you probably already consider this: https://unix.stackexchange.com/questions/30515/how-to-setup-port-redirection-after-a-ssh-connection-has-been-opened

[hamed6]

Im facing the same problem. installed "remote development" extension and tried to connect through SSH Tunnel but Im getting:

Connected to SSH Host - Please do not close this terminal

I tried to open new terminal and surprisingly the second one worked while first terminal still trying to connect:

[roblourens]

@hamed6 this is expected, the first terminal is keeping the SSH port tunnel open. In the future please open your own issue.

[happyringtail]

I was confused with this too. And I installed this extension in windows and Mac, the windows one didn't show message like this at all.
Connected to SSH Host - Please do not close this terminal

A little more description after this would help. e.g,
Connected to SSH Host - Please keep this SSH Tunnel open and have fun with new terminal!

[roblourens]

We now use dynamic port forwarding by default and only have to create one ssh connection. That should solve the issue that some people have had here.

If you are assigned to a different node each time you connect, then you may also have an issue with connecting to a workspace and editing files, then ending up on a new node that doesn't have those files. I think it's likely that a system like this would mount your home dir using a network drive to share files though.

Also in this case, if you lose your connection then reconnecting may fail because we would try to reconnect to a new node that doesn't have the running vscode server. But I will close this because I don't think there's anything I can do about that. The workaround for that would be to modify your ssh config so that you are connecting to exactly the same node each time.