====== Using VSCode Backend on Caviness======

==== Download and install ====
  - Install the [[http://code.visualstudio.com/download|Stable Build VSCode]] on the local machine. **DO NOT** install the VSCode Insiders Build, as it will not work with the proxy. If the version of VSCode downloaded is newer than version 1.90, please make sure to do these [[software:vscode:caviness#additional-steps-required-for-vscode-newer-than-version-190|additional steps]].
  - Install a [[https://code.visualstudio.com/docs/remote/troubleshooting|supported SSH client]].
  - In the extensions tab of VSCode, search for [[https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-ssh|Remote - SSH]] and install.

==== Setting up remote connections ====
First, open VSCode on your computer. You'll see an icon on the left-hand side that looks like a square with some smaller squares inside it; this is the ''Extensions'' icon (labeled 1). Click on that icon to open the ''Extensions'' view. In the search bar at the top, type ''Remote - SSH'' and hit Enter. You'll see the ''Remote - SSH'' extension in the search results. Click on the gearwheel icon (labeled 2) located on the right side of the extension, and a drop-down menu will appear. Select ''Extension Settings'' from this menu.

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The ''remote.SSH'' settings are written as a JSON dictionary and can be edited by clicking on the icon for ''Open Settings (JSON)'' located in the upper right corner below the title bar of the window (marked with large red arrow).This will open a the ''{} settings.json'' file and display each ''remote.SSH'' settings.  **Note:** You will need to create a separate SSH Config file for the 'Remote - SSH' extension without modifying the regular SSH Config file, referred to as ''~/vscode-remote-ssh/config'' below.

To ensure the settings are correct, remove all existing lines in ''{} settings.json'' and replace them with these lines between the ''{'' ''}''
<code>
    "remote.SSH.configFile": "~/vscode-remote-ssh/config",
    "remote.SSH.connectTimeout": 300,
    "remote.SSH.defaultForwardedPorts": [],
    "remote.SSH.maxReconnectionAttempts": 0,
    "remote.SSH.localServerDownload": "off",
    "remote.SSH.lockfilesInTmp": true,
    "remote.SSH.useLocalServer": true,
    "remote.SSH.useExecServer": false,
    "remote.SSH.enableRemoteCommand": true
</code>
 
Clicking on the ''X'' next to ''{} settings.json'' will prompt you to save the settings file. Again keep in mind ''~/vscode-remote-ssh/config'' is used for illustrative purposes. You can change this to specify the path and filename of choice. The ''Connect Timeout'' is set to 300 seconds in order to allow Slurm enough time to schedule and launch the interactive job.

<note important>
The path of ''{} settings.json'' can be found at:
          

^ Linux    |~/.config/Code/User/settings.json |
^ Windows   | %APPDATA%\Code\User\settings.json     | 
^ Mac | ~/Library/Application\ Support/Code/User/settings.json|

</note>

Now, click on the ''X'' to close the ''Settings'' tab for the ''Remote - SSH Extensions Settings''. On the lower left corner, click the button ''Open a Remote Window''(or ''F1''), select ''Connect Current Window to Host'' and then ''Configure SSH Hosts''. 

{{:software:vscode:vscode-4.png?400|}}
{{:software:vscode:vscode-5.png?400|}}
{{:software:vscode:vscode-6.png?400|}}
{{:software:vscode:vscode-7.png?400|}}

It will open the Config file located in the path specified by ''~/vscode-remote-ssh/config''. You may have multiple configurations used for Caviness with different Host definitions. For example, in this Config file, ''Host Caviness'' starts the interactive job on the ''devel'' partition and requests 4 CPUs for the remote shell to use. '' Host CavinessGPU'' requests a P100 GPU for the interactive job on the ''devel'' partition.

For this example,  the Config file ''~/vscode-remote-ssh/config'' contains the following definitions  (remember User ''traine'' should be replace with your username as well as possible partition and other options)
<code>
# Read more about SSH config files: https://linux.die.net/man/5/ssh_config
# Use CPU
Host Caviness
    HostName caviness.hpc.udel.edu
    User traine
    Forwardx11 no
    ForwardX11Trusted no
    RemoteCommand vscode-shell-proxy -g it_css --salloc-arg=--partition=devel --salloc-arg=--cpus-per-task=4

# Use GPU
Host CavinessGPU
    HostName caviness.hpc.udel.edu
    User traine
    Forwardx11 no
    ForwardX11Trusted no
    RemoteCommand vscode-shell-proxy -g it_css --salloc-arg=--partition=devel --salloc-arg=--gres=gpu:p100
</code>


<note important>
''vscode-shell-proxy'' does not work properly for MPI over multiple nodes on Caviness due to an older version of Slurm, please do not attempt to use multiple nodes like '-N 2'.  Instead, if you need to use VSCode for MPI over multiple nodes,  do NOT use ''vscode-shell-proxy'', and set the hostname to either ''login00.caviness.hpc.udel.edu'' or ''login01.caviness.hpc.udel.edu''.
<code>
Host CavinessMPI
    HostName login00.caviness.hpc.udel.edu
    User traine
    Forwardx11 no
    ForwardX11Trusted no
</code>
Then open a terminal window, and use ''salloc  %%--%%nodes= %%--%%ntasks= '' to start the multinode interactive session.
</note>

The ''vscode-shell-proxy'' is the Python script executed on the login node to connect the interactive job.  A symbolic link ''vscode-shell-proxy'' was added to /usr/local/bin on the login nodes. The ''%%--%%help'' command show the usage of ''vscode-shell-proxy'':

<code>
usage: vscode-shell-proxy.py [-h] [-v] [-q] [-l <PATH>] [-0 <PATH>] [-1 <PATH>] [-2 <PATH>] [-b <N>] [-B <N>]
                             [-H <HOSTNAME>] [-p <N>] [-g <WORKGROUP>] [-S <SLURM-ARG>]

vscode remote shell proxy

options:
  -h, --help            show this help message and exit
  -v, --verbose         increase the level of output as the program executes
  -q, --quiet           decrease the level of output as the program executes
  -l <PATH>, --log-file <PATH>
                        direct all logging to this file rather than stderr; the token "[PID]" will be replaced with
                        the running pid
  -0 <PATH>, --tee-stdin <PATH>
                        send a copy of input to the script stdin to this file; the token "[PID]" will be replaced with
                        the running pid
  -1 <PATH>, --tee-stdout <PATH>
                        send a copy of output to the script stdout to this file; the token "[PID]" will be replaced
                        with the running pid
  -2 <PATH>, --tee-stderr <PATH>
                        send a copy of output to the script stderr to this file; the token "[PID]" will be replaced
                        with the running pid
  -b <N>, --backlog <N>
                        number of backlogged connections held by the proxy socket (see man page for listen(), default
                        8)
  -B <N>, --byte-limit <N>
                        maximum bytes read at one time per socket (default 4096
  -H <HOSTNAME>, --listen-host <HOSTNAME>
                        the client-facing TCP proxy should bind to this interface (default 127.0.0.1; use 0.0.0.0 for
                        all interfaces)
  -p <N>, --listen-port <N>
                        the client-facing TCP proxy port (default 0 implies a random port is chosen)
  -g <WORKGROUP>, --group <WORKGROUP>, --workgroup <WORKGROUP>
                        the workgroup used to submit the vscode job
  -S <SLURM-ARG>, --salloc-arg <SLURM-ARG>
                        used zero or more times to specify arguments to the salloc command being wrapped (e.g.
                        --partition=<name>, --ntasks=<N>)
</code>
<note important>
Do not run the script ''vscode-shell-proxy'' itself on the login node, as it will start a remote interactive session.
</note>

==== Connect VSCode to Compute Node ====
Now, we can connect the VSCode to the compute node. Follow the similar steps when adding the Config file from the [[:software:vscode:caviness#setting-up-remote-connections|Setting up Remote Connections]] except step 3. Since we created the host named ''Caviness'', choose it and enter the credentials for Caviness login (or use [[software:vscode:caviness#using-ssh-keys|SSH keys]]). 

{{:software:vscode:vscode-4.png?400|}}
{{:software:vscode:vscode-5.png?400|}}
{{:software:vscode:vscode-8.png?400|}}

After successful login, you will now connect to the compute node. Open the built-in terminal in VSCode and print the hostname,

<code>
[(it_css:traine)@r00n56 ~]$ hostname
r00n56.localdomain.hpc.udel.edu
</code>

You can open the file on your home directory in Caviness and edit it. After completing the job, click ''Close Remote Connection'' to stop the job.
{{:software:vscode:vscode-9.png?400|}}

==== Additional Steps required for VSCode newer than version 1.90 ====

Recent releases of VSCode require a newer version of ''wget'' than the system's default version on Caviness. This discrepancy can result in a "connection failed" error as reported and discussed [[https://groups.google.com/a/udel.edu/g/hpc-ask/c/l8jvUHk2bUE/m/mAzWz7k5AAAJ|here]]. To resolve this, wget v1.24.5 has been installed at ''/opt/shared/wget/bin/wget''. 

<note important>

To ensure the updated version of wget is used by default, you can create a symbolic link in your ''~/bin'' directory by following the steps below:


1. Create a bin directory in your home directory (if it doesn't already exist):
<code>mkdir ~/bin</code>


2. Create a symbolic link for wget v1.24.5 in the ''~/bin'' directory:
<code>ln -s /opt/shared/wget/1.24.5/bin/wget ~/bin/wget</code>

3. Modify your ''~/.bash_profile'' on Caviness:

Update the PATH variable by changing the line from:
<code>PATH=$PATH:$HOME/.local/bin:$HOME/bin</code> 
to:
<code>PATH=$HOME/.local/bin:$HOME/bin:$PATH</code>

4. Apply the changes to your ''~/.bash_profile'':

After making the changes, you can apply them by either logging out and back in or by running:
<code>source ~/.bash_profile</code>

</note>

==== Using SSH keys ====
SSH public key authentication is a secure way to authenticate with an SSH host by combining a local "private" key with a "public" key associated with your user account. Once you set up the SSH keys, you will not need to enter the password for every login. If you have previously set up your SSH keys (i.e. you can login with SSH to Caviness without having to enter your password), then you do not need to do this step unless you want to create SSH keys specifically for VSCode. Please only generate the SSH keys on the trusted computer. For macOS / Linux, you can run the following command in a local terminal:
<code>
ssh-keygen -t ed25519 -f ~/.ssh/id_ed25519-remote-ssh
export USER_AT_HOST="your-user-name@caviness.hpc.udel.edu"
export PUBKEYPATH="$HOME/.ssh/id_ed25519-remote-ssh.pub"
ssh-copy-id -i "$PUBKEYPATH" "$USER_AT_HOST"
</code>
For Windows, run the following command in a local PowerShell as administrator:
<code>
ssh-keygen -t ed25519 -f "$HOME\.ssh\id_ed25519-remote-ssh"
$USER_AT_HOST="your-user-name@caviness.hpc.udel.edu"
$PUBKEYPATH="$HOME\.ssh\id_ed25519-remote-ssh.pub"

$pubKey=(Get-Content "$PUBKEYPATH" | Out-String); ssh "$USER_AT_HOST" "mkdir -p ~/.ssh && chmod 700 ~/.ssh && echo '${pubKey}' >> ~/.ssh/authorized_keys && chmod 600 ~/.ssh/authorized_keys"

</code>

Open VSCode and run "Remote-SSH: Open Configuration File" in the Command Palette (F1). Then, select ''~/vscode-remote-ssh/config'' and add or modify a host entry as shown below:

<code>
Host Caviness
    HostName caviness.hpc.udel.edu
    User traine
    Forwardx11 no
    ForwardX11Trusted no
    RemoteCommand vscode-shell-proxy -g it_css --salloc-arg=--partition=devel --salloc-arg=--cpus-per-task=4
    IdentityFile ~/.ssh/id_ed25519-remote-ssh
</code>

For more information, please refer to [[https://code.visualstudio.com/docs/remote/troubleshooting|SSH tips]].