Remote snapshotter extension for containerd

Snapshots crate implements containerd's proxy plugin for snapshotting. It aims hide the underlying complexity of GRPC interfaces, streaming, and request/response conversions and provide one Snapshots trait to implement.

containerd Documentation

Proxy plugins

A proxy plugin is configured using containerd's config file and will be loaded alongside the internal plugins when containerd is started. These plugins are connected to containerd using a local socket serving one of containerd's GRPC API services. Each plugin is configured with a type and name just as internal plugins are.

How to use from containerd

Add the following to containerd's configuration file: toml [proxy_plugins] [proxy_plugins.custom] type = "snapshot" address = "/tmp/snap2.sock"

Start daemons and try pulling an image with custom snapshotter: ```bash

Start containerd daemon

$ containerd --config /path/config.toml

Run remote snapshotter instance

$ cargo run --example snapshotter /tmp/snap2.sock

Now specify the snapshotter when pulling an image

$ ctr i pull --snapshotter custom docker.io/library/hello-world:latest ```

Getting started

Snapshotters are required to implement Snapshotter trait (which is very similar to containerd's Snapshotter interface).

```rust

[derive(Default)]

struct Example;

[snapshots::tonic::async_trait]

impl snapshots::Snapshotter for Example { type Error = ();

async fn stat(&self, key: String) -> Result<Info, Self::Error> {
    info!("Stat: {}", key);
    Ok(Info::default())
}

// ...

async fn commit(
    &self,
    name: String,
    key: String,
    labels: HashMap<String, String>,
) -> Result<(), Self::Error> {
    info!("Commit: name={}, key={}, labels={:?}", name, key, labels);
    Ok(())
}

} ```

The library provides snapshots::server for convenience to wrap the implementation into a GRPC server, so it can be used with tonic like this:

```rust

use snapshots::tonic::transport::Server;

Server::builder() .addservice(snapshots::server(example)) .servewith_incoming(incoming) .await .expect("Serve failed"); ```