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Nydus Snapshotter

Nydus-snapshotter is a non-core sub-project of containerd.

Nydus snapshotter is an external plugin of containerd for Nydus image service which implements a chunk-based content-addressable filesystem on top of a called RAFS (Registry Acceleration File System) format that improves the current OCI image specification, in terms of container launching speed, image space, and network bandwidth efficiency, as well as data integrity with several runtime backends: FUSE, virtiofs and in-kernel EROFS.

Nydus supports lazy pulling feature since pulling image is one of the time-consuming steps in the container lifecycle. Lazy pulling here means a container can run even the image is partially available and necessary chunks of the image are fetched on-demand. Apart from that, Nydus also supports (e)Stargz and OCI (by using zran) lazy pulling directly WITHOUT any explicit conversion.

For more details about how to build Nydus container image, please refer to nydusify conversion tool and acceld.

Architecture

Architecture Based on FUSE

Architecture Based on Fscache/Erofs

Building

Just invoke make and check out the output executable binary ./bin/containerd-nydus-grpc

make

Integrate Nydus-snapshotter into Containerd

The following document will describe how to manually configure containerd + Nydus snapshotter. If you want to run Nydus snapshotter in Kubernetes cluster, you can try to use helm or run nydus snapshotter as a container. You can refer to this documentation.

Containerd provides a general mechanism to exploit different types of snapshotters. Please ensure your containerd's version is 1.4.0 or above. Add Nydus as a proxy plugin into containerd's configuration file which may be located at /etc/containerd/config.toml.

# The `address` field specifies through which socket snapshotter and containerd communicate.
[proxy_plugins]
  [proxy_plugins.nydus]
    type = "snapshot"
    address = "/run/containerd-nydus/containerd-nydus-grpc.sock"

Restart your containerd service making the change take effect. Assume that your node is systemd based, restart the service as below:

systemctl restart containerd

Get Nydus Binaries

Get nydusd nydus-image and nydusctl binaries from nydus releases page. It's suggested to install the binaries to your system path. nydusd is FUSE userspace daemon and a vhost-user-fs backend. Nydus-snapshotter will fork a nydusd process when necessary.

Configure Nydus

Please follow instructions to configure nydus in order to make it work properly in your environment.

Start Nydus Snapshotter

Nydus-snapshotter is implemented as a proxy plugin (containerd-nydus-grpc) for containerd.

Assume your server is systemd based, install nydus-snapshotter: Note: nydusd and nydus-image should be found from $PATH.

make install
systemctl restart containerd

Or you can start nydus-snapshotter manually.

# `--nydusd` specifies the path to nydusd binary. If `nydusd` and `nydus-image` are installed, `--nydusd` and `--nydus-image`can be omitted.
# Otherwise, provide them in below command line.
# `address` is the domain socket that you configured in containerd configuration file
# `--nydusd-config` is the path to `nydusd` configuration file
# The default nydus-snapshotter work directory is located at `/var/lib/containerd-nydus`

$ sudo ./containerd-nydus-grpc --config /etc/nydus/config.toml --nydusd-config /etc/nydus/nydusd-config.json --log-to-stdout

Validate Nydus-snapshotter Setup

Utilize containerd's ctr CLI command to validate if nydus-snapshotter is set up successfully.

$ ctr -a /run/containerd/containerd.sock plugin ls
TYPE                            ID                       PLATFORMS      STATUS
io.containerd.snapshotter.v1    nydus                    -              ok

Optimize Nydus Image as per Workload

Nydus usually prefetch image data to local filesystem before a real user on-demand read. It helps to improve the performance and availability. A containerd NRI plugin container image optimizer can be used to generate nydus image building suggestions to optimize your nydus image making the nydusd runtime match your workload IO pattern. The optimized nydus image has a better performance.

Quickstart Container with Lazy Pulling

Start Container on single Node

Start container using nerdctl (>=v0.22) which has native nydus support with nydus-snapshotter.

# Start container by `nerdctl`
nerdctl --snapshotter nydus run ghcr.io/dragonflyoss/image-service/nginx:nydus-latest

Start Container in Kubernetes Cluster

Change containerd's CRI configuration:

[plugins."io.containerd.grpc.v1.cri".containerd]
   snapshotter = "nydus"
   disable_snapshot_annotations = false

Use crictl to debug starting container via Kubernetes CRI. Dry run steps of using crictl can be found in documents.

Setup with nydus-snapshotter image

We can also use the nydus-snapshotter container image when we want to put Nydus stuffs inside a container. See the nydus-snapshotter example for how to setup and use it.

Integrate with Dragonfly to Distribute Images by P2P

Nydus is a sub-project of Dragonfly. So it closely works with Dragonfly to distribute container images in a fast and efficient P2P fashion to reduce network latency and lower the pressure on a single-point of the registry.

Quickstart Dragonfly & Nydus in Kubernetes

We recommend using the Dragonfly P2P data distribution system to further improve the runtime performance of Nydus images.

If you want to deploy Dragonfly and Nydus at the same time, please refer to this Quick Start.

Config Dragonfly mode

Dragonfly supports both mirror mode and HTTP proxy mode to boost the containers startup. It is suggested to use Dragonfly mirror mode. To integrate with Dragonfly in the mirror mode, please provide registry mirror in nydusd's json configuration file in section device.backend.mirrors

{
  "mirrors": [
    {
      "host": "http://127.0.0.1:65001",
      "headers": "https://index.docker.io/v1/"
    }
  ]
}

Hot updating mirror configurations

In addition to setting the registry mirror in nydusd's json configuration file, nydus-snapshotter also supports hot updating mirror configurations. You can set the configuration directory in nudus-snapshotter's toml configuration file with remote.mirrors_config.dir. The empty remote.mirrors_config.dir means disabling it.

[remote.mirrors_config]
dir = "/etc/nydus/certs.d"

Configuration file is compatible with containerd's configuration file in toml format.

[host]
  [host."http://127.0.0.1:65001"]
    [host."http://127.0.0.1:65001".header]
      # NOTE: For Dragonfly, the HTTP scheme must be explicitly specified.
      X-Dragonfly-Registry = ["https://p2p-nydus.com"]

Mirror configurations loaded from nydusd's json file will be overwritten before pulling image if the valid mirror configuration items loaded from remote.mirrors_config.dir are greater than 0.

Community

Nydus aims to form a vendor-neutral opensource image distribution solution to all communities. Questions, bug reports, technical discussion, feature requests and contribution are always welcomed!

We're very pleased to hear your use cases any time. Feel free to reach/join us via Slack and/or Dingtalk.

Slack: Nydus Workspace
Twitter: @dragonfly_oss
Dingtalk: 34971767

Technical Meeting: Every Wednesday at 06:00 UTC (Beijing, Shanghai 14:00), please see our HackMD page for more information.

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