sglang/docs/developer/development_guide_using_docker.md

# Development Guide Using Docker

## Setup VSCode on a Remote Host
(Optional - you can skip this step if you plan to run the SGLang dev container locally)

1. In the remote host, download `code` from [https://code.visualstudio.com/docs/?dv=linux64cli](https://code.visualstudio.com/download) and run `code tunnel` in a shell.

Example
```bash
wget https://vscode.download.prss.microsoft.com/dbazure/download/stable/fabdb6a30b49f79a7aba0f2ad9df9b399473380f/vscode_cli_alpine_x64_cli.tar.gz
tar xf vscode_cli_alpine_x64_cli.tar.gz

# https://code.visualstudio.com/docs/remote/tunnels
./code tunnel
```

2. In your local machine, press F1 in VSCode and choose "Remote Tunnels: Connect to Tunnel".

## Setup Docker Container

### Option 1. Use the default dev container automatically from VSCode
There is a `.devcontainer` folder in the SGLang repository root folder to allow VSCode to automatically start up within dev container. You can read more about this VSCode extension in VSCode official document [Developing inside a Container](https://code.visualstudio.com/docs/devcontainers/containers).
![image](https://github.com/user-attachments/assets/6a245da8-2d4d-4ea8-8db1-5a05b3a66f6d)
(*Figure 1: Diagram from VSCode official documentation [Developing inside a Container](https://code.visualstudio.com/docs/devcontainers/containers).*)

To enable this, you only need to:
1. Start Visual Studio Code and install the [VSCode dev container extension](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-containers).
2. Press F1, type and choose "Dev Container: Open Folder in Container.
3. Input the `sglang` local repo path in your machine and press enter.

The first time you open it in the dev container might take longer due to docker pull and build. Once it's successful, you should set on your status bar at the bottom left displaying that you are in a dev container:

![image](https://github.com/user-attachments/assets/650bba0b-c023-455f-91f9-ab357340106b)

Now when you run `sglang.launch_server` in the VSCode terminal or start debugging using F5, the SGLang server will be started in the dev container with all your local changes applied automatically:

![image](https://github.com/user-attachments/assets/748c85ba-7f8c-465e-8599-2bf7a8dde895)


### Option 2. Start up containers manually (advanced)

The following startup command is an example for internal development by the SGLang team. You can **modify or add directory mappings as needed**, especially for model weight downloads, to prevent repeated downloads by different Docker containers.

❗️ **Note on RDMA**

    1. `--network host` and `--privileged` are required by RDMA. If you don't need RDMA, you can remove them but keeping them there does not harm. Thus, we enable these two flags by default in the commands below.
    2. You may need to set `NCCL_IB_GID_INDEX` if you are using RoCE, for example: `export NCCL_IB_GID_INDEX=3`.

```bash
# Change the name to yours
docker run -itd --shm-size 32g --gpus all -v <volumes-to-mount> --ipc=host --network=host --privileged --name sglang_dev lmsysorg/sglang:dev /bin/zsh
docker exec -it sglang_dev /bin/zsh
```
Some useful volumes to mount are:
1. **HuggingFace model cache**: mounting model cache can avoid the need to re-download every time docker restarts. Default location on Linux is `~/.cache/huggingface/`.
2. **SGLang repository**: code changes in the SGLang local repository will be automatically synced to the .devcontainer.

Example 1: Mounting local cache folder `/opt/dlami/nvme/.cache` but not the SGLang repo. Use this when you prefer to manually transfer local code changes to the devcontainer.
```bash
docker run -itd --shm-size 32g --gpus all -v /opt/dlami/nvme/.cache:/root/.cache --ipc=host --network=host --privileged --name sglang_zhyncs lmsysorg/sglang:dev /bin/zsh
docker exec -it sglang_zhyncs /bin/zsh
```
Example 2: Mounting both the HuggingFace cache and the local SGLang repo. Local code changes are automatically synced to the devcontainer as SGLang is installed in editable mode in the dev image.
```bash
docker run -itd --shm-size 32g --gpus all -v $HOME/.cache/huggingface/:/root/.cache/huggingface -v $HOME/src/sglang:/sgl-workspace/sglang --ipc=host --network=host --privileged --name sglang_zhyncs lmsysorg/sglang:dev /bin/zsh
docker exec -it sglang_zhyncs /bin/zsh
```
## Debug SGLang with VSCode Debugger
1. (Create if it does not exist) open `launch.json` in VSCode.
2. Add the following config and save. Please note that you can edit the script as needed to apply different parameters or debug a different program (e.g. benchmark script).
     ```JSON
       {
          "version": "0.2.0",
          "configurations": [
              {
                  "name": "Python Debugger: launch_server",
                  "type": "debugpy",
                  "request": "launch",
                  "module": "sglang.launch_server",
                  "console": "integratedTerminal",
                  "args": [
                      "--model-path", "meta-llama/Llama-3.2-1B",
                      "--host", "0.0.0.0",
                      "--port", "30000",
                      "--trust-remote-code",
                  ],
                  "justMyCode": false
              }
          ]
      }
    ```

3. Press "F5" to start. VSCode debugger will ensure that the program will pause at the breakpoints even if the program is running at remote SSH/Tunnel host + dev container.

## Profile

```bash
# Change batch size, input, output and add `disable-cuda-graph` (for easier analysis)
# e.g. DeepSeek V3
nsys profile -o deepseek_v3 python3 -m sglang.bench_one_batch --batch-size 1 --input 128 --output 256 --model deepseek-ai/DeepSeek-V3 --trust-remote-code --tp 8 --disable-cuda-graph
```

## Evaluation

```bash
# e.g. gsm8k 8 shot
python3 benchmark/gsm8k/bench_sglang.py --num-questions 2000 --parallel 2000 --num-shots 8
```