nixl-cu12 0.10.0
NIXL Python API
Requires Python: >=3.10

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# NVIDIA Inference Xfer Library (NIXL)

NVIDIA Inference Xfer Library (NIXL) is targeted for accelerating point to point communications in AI inference frameworks such as NVIDIA Dynamo, while providing an abstraction over various types of memory (e.g., CPU and GPU) and storage (e.g., file, block and object store) through a modular plug-in architecture.

[![License](https://img.shields.io/badge/License-Apache_2.0-blue.svg)](https://opensource.org/licenses/Apache-2.0)
[![GitHub Release](https://img.shields.io/github/v/release/ai-dynamo/nixl)](https://github.com/ai-dynamo/nixl/releases/latest)

## Documentation and Resources

* [NIXL overview](https://github.com/ai-dynamo/nixl/blob/main/docs/nixl.md) - Core concepts/architecture overview (`docs/nixl.md`)

* [Python API](https://github.com/ai-dynamo/nixl/blob/main/docs/python_api.md) - Python API usage and examples (`docs/python_api.md`)

* [Backend guide](https://github.com/ai-dynamo/nixl/blob/main/docs/BackendGuide.md) - Backend/plugin development guide (`docs/BackendGuide.md`)

* [Telemetry](https://github.com/ai-dynamo/nixl/blob/main/docs/telemetry.md) - Observability and telemetry details (`docs/telemetry.md`)

* [Doxygen guide](https://github.com/ai-dynamo/nixl/blob/main/docs/doxygen/nixl_doxygen.md) - API/class diagrams overview (`docs/doxygen/nixl_doxygen.md`)

* [Doxygen images](https://github.com/ai-dynamo/nixl/tree/main/docs/doxygen) - Diagram assets (`docs/doxygen/`)

* [NIXLBench docs](https://github.com/ai-dynamo/nixl/blob/main/benchmark/nixlbench/README.md) - Benchmark usage guide (`benchmark/nixlbench/README.md`)

* [KVBench docs](https://github.com/ai-dynamo/nixl/tree/main/benchmark/kvbench/docs) - KVBench workflows and tutorials (`benchmark/kvbench/docs/`)

## Supported Platforms
NIXL is supported on a Linux environment only. It is tested on Ubuntu (22.04/24.04) and Fedora. macOS and Windows are not currently supported; use a Linux host or container/VM.

## Pre-build Distributions
### PyPI Wheel

The nixl python API and libraries, including UCX, are available directly through PyPI.
For example, if you have a GPU running on a Linux host, container, or VM, you can do the following install:

It can be installed for CUDA 12 with:

```
pip install nixl[cu12]
```

For CUDA 13 with:

```
pip install nixl[cu13]
```

For backwards compatibility, `pip install nixl` installs automatically `nixl[cu12]`, continuing to work seamlessly for CUDA 12 users without requiring changes to downstream project dependencies.

If both `nixl-cu12` and `nixl-cu13` are installed at the same time in an environment, `nixl-cu13` takes precedence.

## Prerequisites for source build (Linux)
### Ubuntu:

`$ sudo apt install build-essential cmake pkg-config`

### Fedora:

`$ sudo dnf install gcc-c++ cmake pkg-config`

### Python

`$ pip3 install meson ninja pybind11 tomlkit`

### UCX

NIXL was tested with UCX version 1.20.x.

[GDRCopy](https://github.com/NVIDIA/gdrcopy) is available on Github and is necessary for maximum performance, but UCX and NIXL will work without it.

```
$ git clone https://github.com/openucx/ucx.git
$ cd ucx
$ git checkout v1.20.x
$ ./autogen.sh
$ ./contrib/configure-release-mt       \
    --enable-shared                    \
    --disable-static                   \
    --disable-doxygen-doc              \
    --enable-optimizations             \
    --enable-cma                       \
    --enable-devel-headers             \
    --with-cuda=<cuda install>         \
    --with-verbs                       \
    --with-dm                          \
    --with-gdrcopy=<gdrcopy install>
$ make -j
$ make -j install-strip
$ ldconfig
```

### ETCD (Optional)
NIXL can use ETCD for metadata distribution and coordination between nodes in distributed environments. To use ETCD with NIXL:
#### ETCD Server and Client
 ```
$ sudo apt install etcd etcd-server etcd-client

# Or use Docker
$ docker run -d -p 2379:2379 quay.io/coreos/etcd:v3.5.1
```

#### ETCD CPP API
Installed from https://github.com/etcd-cpp-apiv3/etcd-cpp-apiv3

```
$ sudo apt install libgrpc-dev libgrpc++-dev libprotobuf-dev protobuf-compiler-grpc
$ sudo apt install libcpprest-dev
$ git clone https://github.com/etcd-cpp-apiv3/etcd-cpp-apiv3.git
$ cd etcd-cpp-apiv3
$ mkdir build && cd build
$ cmake ..
$ make -j$(nproc) && make install
```

### Additional plugins

Some plugins may have additional build requirements, see them here:

- [Mooncake](src/plugins/mooncake/README.md)
- [POSIX](src/plugins/posix/README.md)
- [GDS](src/plugins/cuda_gds/README.md)

## Getting started
### Build & install

```
$ meson setup <name_of_build_dir>
$ cd <name_of_build_dir>
$ ninja
$ ninja install
```

### Build Options

#### Release build (default)

```bash
$ meson setup <name_of_build_dir>
```

#### Debug build

```bash
$ meson setup <name_of_build_dir> --buildtype=debug
```

#### NIXL-specific build options

```bash
# Example with custom options
$ meson setup <name_of_build_dir> \
    -Dbuild_docs=true \           # Build Doxygen documentation
    -Ducx_path=/path/to/ucx \     # Custom UCX installation path
    -Dinstall_headers=true \      # Install development headers
    -Ddisable_gds_backend=false   # Enable GDS backend
```

Common build options:
- `build_docs`: Build Doxygen documentation (default: false)
- `ucx_path`: Path to UCX installation (default: system path)
- `install_headers`: Install development headers (default: true)
- `disable_gds_backend`: Disable GDS backend (default: false)
- `cudapath_inc`, `cudapath_lib`: Custom CUDA paths
- `static_plugins`: Comma-separated list of plugins to build statically
- `enable_plugins`: Comma-separated list of plugins to build (e.g. `-Denable_plugins=UCX,POSIX`). Cannot be used with `disable_plugins`.
- `disable_plugins`: Comma-separated list of plugins to exclude (e.g. `-Ddisable_plugins=GDS`). Cannot be used with `enable_plugins`.

#### Environment Variables

There are a few environment variables that can be set to configure the build:
- `NIXL_NO_STUBS_FALLBACK`: If not set or 0, build NIXL stub library if the library build fails

### Building Documentation

If you have Doxygen installed, you can build the documentation:

```bash
# Configure with documentation enabled
$ meson setup <name_of_build_dir> -Dbuild_docs=true
$ cd <name_of_build_dir>
$ ninja

# Documentation will be generated in <name_of_build_dir>/html
# After installation (ninja install), documentation will be available in <prefix>/share/doc/nixl/
```

### Python Interface

NIXL provides Python bindings through pybind11. For detailed Python API documentation, see [docs/python_api.md](docs/python_api.md).

The preferred way to install the Python bindings is through pip from PyPI:

```bash
pip install nixl[cu12]
```

Or for CUDA 13 with:

```bash
pip install nixl[cu13]
```

#### Installation from source

Prerequisites:

- `uv`: https://docs.astral.sh/uv/getting-started/installation/
- `tomlkit`: https://pypi.org/project/tomlkit/
- `PyTorch`: https://pytorch.org/get-started/locally/

`uv` is always required *even if* you have another kind of Python virtual environment manager or if you are using a system-wide Python installation without using a virtual environment.

Example with `uv` Python virtual environment:

```
curl -LsSf https://astral.sh/uv/install.sh | sh
export PATH="$HOME/.local/bin:${PATH}"

uv venv .venv --python 3.12
source .venv/bin/activate
uv pip install tomlkit
```

Example with python-virtualenv:

```
curl -LsSf https://astral.sh/uv/install.sh | sh
export PATH="$HOME/.local/bin:${PATH}"

python3 -m venv .venv
source .venv/bin/activate
pip install tomlkit
```

Example with system-wide Python installation without using a virtual environment:

```
curl -LsSf https://astral.sh/uv/install.sh | sh
export PATH="$HOME/.local/bin:${PATH}"

pip install tomlkit
```

Then install PyTorch following the instructions on the PyTorch website: https://pytorch.org/get-started/locally/

After installing the prerequisites, you can build and install the NIXL binaries and the Python bindings from source. You have to:

1. Build NIXL binaries and install them
2. Build and install the CUDA platform-specific package (`nixl-cu12` or `nixl-cu13`)
3. Build and install the `nixl` meta-package

**For CUDA 12:**

```
pip install .
meson setup build
ninja -C build install
pip install build/src/bindings/python/nixl-meta/nixl-*-py3-none-any.whl
```

**For CUDA 13:**

```
pip install .
./contrib/tomlutil.py --wheel-name nixl-cu13 pyproject.toml
meson setup build
ninja -C build install
pip install build/src/bindings/python/nixl-meta/nixl-*-py3-none-any.whl
```

To check if the installation is successful, you can run the following command:

```
python3 -c "import nixl; agent = nixl.nixl_agent('agent1')"
```

which should print:

```
2026-01-08 13:36:27 NIXL INFO    _api.py:363 Backend UCX was instantiated
2026-01-08 13:36:27 NIXL INFO    _api.py:253 Initialized NIXL agent: agent1
```

You can also run a complete Python example to test the installation:

```
python3 examples/python/expanded_two_peers.py --mode=target --use_cuda=true --ip=127.0.0.1 --port=4242 &
sleep 5
python3 examples/python/expanded_two_peers.py --mode=initiator --use_cuda=true --ip=127.0.0.1 --port=4242
```

For more Python examples, see [examples/python/](examples/python/).

### Rust Bindings
#### Build
- Use `-Drust=true` meson option to build rust bindings.
- Use `--buildtype=debug` for a debug build (default is release).
- Or build manually:
    ```bash
    $ cargo build --release
    ```
#### Install
The bindings will be installed under `nixl-sys` in the configured installation prefix.
Can be done using ninja, from project build directory:
```bash
$ ninja install
```

#### Test
```
# Rust bindings tests
$ cargo test
```

Use in your project by adding to `Cargo.toml`:
```toml
[dependencies]
nixl-sys = { path = "path/to/nixl/bindings/rust" }
```

### Other build options
See [contrib/README.md](contrib/README.md) for more build options.

### Building Docker container
To build the docker container, first clone the current repository. Also make sure you are able to pull docker images to your machine before attempting to build the container.

Run the following from the root folder of the cloned NIXL repository:
```
$ ./contrib/build-container.sh
```

By default, the container is built with Ubuntu 24.04. To build a container for Ubuntu 22.04 use the --os option as follows:
```
$ ./contrib/build-container.sh --os ubuntu22
```

To see all the options supported by the container use:
```
$ ./contrib/build-container.sh -h
```

The container also includes a prebuilt python wheel in /workspace/dist if required for installing/distributing. Also, the wheel can be built with a separate script (see below).

### Building the python wheel
The contrib folder also includes a script to build the python wheel with the UCX dependencies. Note, that UCX and other NIXL dependencies are required to be installed.
```
$ ./contrib/build-wheel.sh
```

## Running with ETCD
NIXL can use ETCD for metadata exchange between distributed nodes. This is especially useful in containerized or cloud-native environments.

### Environment Setup
To use ETCD with NIXL, set the following environment variables:

```bash
# Set ETCD endpoints (required) - replace localhost with the hostname of the etcd server
export NIXL_ETCD_ENDPOINTS="http://localhost:2379"

# Set ETCD namespace (optional, defaults to /nixl/agents)
export NIXL_ETCD_NAMESPACE="/nixl/agents"
```

### Running the ETCD Example
NIXL includes an example demonstrating metadata exchange and data transfer using ETCD:

```bash
# Start an ETCD server if not already running
# For example:
# docker run -d -p 2379:2379 quay.io/coreos/etcd:v3.5.1

# Set the ETCD env variables as above

# Run the example. The two agents in the example will exchange metadata through ETCD
# and perform data transfers
./<nixl_build_path>/examples/nixl_etcd_example
```

### nixlbench Benchmark
For more comprehensive testing, the nixlbench benchmarking tool supports ETCD for worker coordination:

```bash
# Build nixlbench (see benchmark/nixlbench/README.md for details)
cd benchmark/nixlbench
meson setup build && cd build && ninja

# Run benchmark with ETCD
./nixlbench --etcd-endpoints http://localhost:2379 --backend UCX --initiator_seg_type VRAM
```

## Code Examples

* [C++ examples](https://github.com/ai-dynamo/nixl/tree/main/examples/cpp)

* [Python examples](https://github.com/ai-dynamo/nixl/tree/main/examples/python)

## Contributing

For contribution guidelines, see [CONTRIBUTING.md](https://github.com/ai-dynamo/nixl/blob/main/CONTRIBUTING.md) (`CONTRIBUTING.md`).

## Third-Party Components

This project will download and install additional third-party open source software projects. Review the license terms of these open source projects before use.