VS Code¶

Introduction¶

Visual Studio Code (VS Code) is a code editor widely used for software development. Its integration with remote systems via the Remote-SSH extension allows users to work on HPC clusters directly from their local machines.

However, to facilitate this functionality VS Code runs a program called the vscode-server on the HPC login nodes, which can significantly degrade performance and negatively impact all other users. Moreover, the vscode-server can remain even after users finish their work and disconnect.

Warning

Do not run vscode-server on login nodes. The additional processes can overload these shared resources, leading to slow response times and potential system instability.

Hint

On this page we present different strategies for working with VS Code in our cluster environments while avoiding negatively impacting the login node(s).

Solutions¶

Instead of running VS Code remotely, consider a two-step workflow consisting of

Editing your code and then
Deploying your code only when ready.

This workflow offers several advantages:

Improved Performance: Work on your code without the added latency of a remote connections.
Version Control with Git: Collaborate with others, track changes and revert them if necessary.
Flexible Deployment Options: Deploy updates via git, scp, or sftp to the clusters.

For quick edits on the clusters, such as changing a parameter or a single string inside a file a number of command line editors such as vi or nano are available.

Hint

This approach is considered best practise.

A very usable web version of VS Code is available via Open OnDemand (OOD) on the CoSTAR cluster.

To launch the OOD editor:

Log in to Open OnDemand (OOD) on the CoSTAR cluster.
Navigate to the Dashboard and select Code Server / System Installed App from the landing page or from the Interactive Apps menu.
Fill in the form asking you about number of hours, CPU cores, and amount of RAM.

A reasonable choice could be 5 hours, 4 cores, 8 GB. The lower your request for resources is, the faster it will be granted by the scheduler.
Click on Launch to submit your request.
Once the server has allocated your resources, click on Connect to VS Code.

More about OOD: Open OnDemand

Hint

This approach is suitable for HPC newcomers.

Instead of connecting to the login node, you can configure VS Code to connect directly to a compute node. This method ensures that the vscode-server process runs on a compute node, keeping the shared login nodes free from heavy load. Your local VS-Code IDE can be configured to ask for a compute node on the cluster in an interactive session.

Warning

This solution is the technically most advanced option. It does require a certain understanding of SSH configuration and our cluster’s scheduler.

Step 1: Modify Your SSH Config File

Add the following entries to your SSH config file.

For macOS and Linux users:

Host costar
    HostName costar-login01.surrey.ac.uk
    User ab1234

Host costar-vscode
    ForwardAgent yes
    StrictHostKeyChecking no
    UserKnownHostsFile=/dev/null
    ProxyCommand ssh costar "/usr/bin/salloc --nodes=1 --ntasks-per-node=2 --time=8:00:00 /bin/bash -c 'nc \$SLURM_NODELIST 22'"
    User ab1234

For Windows users, the configuration is nearly identical:

Host costar
    HostName costar-login01.surrey.ac.uk
    User ab1234

Host costar-vscode
    ForwardAgent yes
    StrictHostKeyChecking no
    UserKnownHostsFile=/dev/null
    ProxyCommand ssh costar "/usr/bin/salloc --nodes=1 --ntasks-per-node=2 --time=8:00:00 /bin/bash -c 'nc $SLURM_NODELIST 22'"
    User ab1234

This setup creates a special SSH host entry called costar-vscode that, when connected to, automatically requests and further connects to a compute node via the scheduler.

For connecting to a running job, see the Direct SSH to Compute Nodes guide.

Hint

For detailed instructions on locating and editing your SSH config file, please see our Generating SSH Keys page.
Replace ab1234 with your actual username .
Change the requested resources, i.e., CPU cores, time (set to 2 and 8 hours in the example above) to your liking.
You might need to adjust the SSH connection timeout limit in VS Code (see Optional Steps below) to allow for the time the scheduler needs to allocate your job request.

Step 2: Connect with the VS Code Remote-SSH Extension

Open the Command Palette (Ctrl+Shift+P on Windows/Linux or Cmd+Shift+P on macOS).
Run the command Remote-SSH: Connect to Host....
Select the costar-vscode host from the list.

Optional Steps

Increase the SSH Timeout:

Open VS Code settings (File > Preferences > Settings or Code > Settings.. > Settings).
Search for remote.SSH.connectTimeout and set it to 180 seconds. This should give the scheduler enough time to allocate a compute node.

Set Up Passwordless SSH (optional):

Configure SSH key authentication for a smoother connection process. See Generating SSH Keys for details.