Provide a simplified API when using libcontainer

.github/workflows/action-fmt.yml

@@ -25,11 +25,5 @@ jobs:
       - run: 
           # needed to run rustfmt in nightly toolchain
           rustup toolchain install nightly --component rustfmt
-      - name: Set environment variables for Windows
-        if: runner.os == 'Windows'
-        run: |
-          # required until standalong is implemented for windows (https://github.com/WasmEdge/wasmedge-rust-sdk/issues/54)
-          echo "WASMEDGE_LIB_DIR=C:\Program Files\WasmEdge\lib" >> $env:GITHUB_ENV
-          echo "WASMEDGE_INCLUDE_DIR=C:\Program Files\WasmEdge\include" >> $env:GITHUB_ENV
       - name: Run checks
         run: make check

.github/workflows/action-test-k3s.yml

@@ -37,6 +37,12 @@ jobs:
       - name: run
         timeout-minutes: 5
         run: make test/k3s-${{ inputs.runtime }}
+      # only runs when the previous step fails
+      - name: inspect failed pods
+        if: failure()
+        run: |
+          sudo bin/k3s kubectl get pods --all-namespaces
+          sudo bin/k3s kubectl describe pods --all-namespaces
       - name: cleanup
         if: always()
         run: make test/k3s/clean

Cargo.toml

@@ -37,6 +37,7 @@ sha256 = "1.4.0"
 libcontainer = { version = "0.2", default-features = false }
 windows-sys = { version = "0.48" }
 crossbeam = { version = "0.8.2", default-features = false }
+wat = "*" # Use whatever version wasmtime will make us pull
 
 [profile.release]
 panic = "abort"

README.md

@@ -25,10 +25,19 @@ There are two modes of operation supported:
 1. "Normal" mode where there is 1 shim process per container or k8s pod.
 2. "Shared" mode where there is a single manager service running all shims in process.
 
-In either case you need to implement the `Instance` trait:
+In either case you need to implement a trait to teach runwasi how to use your wasm host.
+
+There are two ways to do this:
+* implementing the `sandbox::Instance` trait
+* or implementing the `container::Engine` trait
+
+The most flexible but complex is the `sandbox::Instance` trait:
 
 ```rust
 pub trait Instance {
+    /// The WASI engine type
+    type Engine: Send + Sync + Clone;
+
     /// Create a new instance
     fn new(id: String, cfg: Option<&InstanceConfig<Self::E>>) -> Self;
     /// Start the instance
@@ -48,6 +57,25 @@ pub trait Instance {
 }
 ```
 
+The `container::Engine` trait provides a simplified API:
+
+```rust
+pub trait Engine: Clone + Send + Sync + 'static {
+    /// The name to use for this engine
+    fn name() -> &'static str;
+    /// Run a WebAssembly container
+    fn run_wasi(&self, ctx: &impl RuntimeContext, stdio: Stdio) -> Result<i32>;
+    /// Check that the runtime can run the container.
+    /// This checks runs after the container creation and before the container starts.
+    /// By it checks that the wasi_entrypoint is either:
+    /// * a file with the `wasm` filetype header
+    /// * a parsable `wat` file.
+    fn can_handle(&self, ctx: &impl RuntimeContext) -> Result<()> { /* default implementation*/ }
+}
+```
+
+After implementing `container::Engine` you can use `container::Instance<impl container::Engine>`, which implements the `sandbox::Instance` trait.
+
 To use your implementation in "normal" mode, you'll need to create a binary which has a main that looks something like this:
 
 ```rust
@@ -67,6 +95,25 @@ fn main() {
 }
 ```
 
+or when using the `container::Engine` trait, like this:
+
+```rust
+use containerd_shim as shim;
+use containerd_shim_wasm::{sandbox::ShimCli, container::{Instance, Engine}}
+
+struct MyEngine {
+    // ...
+}
+
+impl Engine for MyEngine {
+    // ...
+}
+
+fn main() {
+    shim::run::<ShimCli<Instance<Engine>>>("io.containerd.myshim.v1", opts);
+}
+```
+
 Note you can implement your own ShimCli if you like and customize your wasm engine and other things.
 I encourage you to checkout how that is implemented.
 

crates/containerd-shim-wasm/Cargo.toml

@@ -24,6 +24,7 @@ chrono = { workspace = true }
 log = { workspace = true }
 libc = { workspace = true }
 crossbeam = { workspace = true }
+wat = { workspace = true }
 
 [target.'cfg(unix)'.dependencies]
 clone3 = "0.2"

crates/containerd-shim-wasm/src/container/context.rs

@@ -0,0 +1,181 @@
+use std::path::{Path, PathBuf};
+
+use oci_spec::runtime::Spec;
+
+pub trait RuntimeContext {
+    // ctx.args() returns arguments from the runtime spec process field, including the
+    // path to the entrypoint executable.
+    fn args(&self) -> &[String];
+
+    // ctx.entrypoint() returns the entrypoint path from arguments on the runtime
+    // spec process field.
+    fn entrypoint(&self) -> Option<&Path>;
+
+    // ctx.wasi_entrypoint() returns a `WasiEntrypoint` with the path to the module to use
+    // as an entrypoint and the name of the exported function to call, obtained from the
+    // arguments on process OCI spec.
+    // The girst argument in the spec is specified as `path#func` where `func` is optional
+    // and defaults to _start, e.g.:
+    //   "/app/app.wasm#entry" -> { path: "/app/app.wasm", func: "entry" }
+    //   "my_module.wat" -> { path: "my_module.wat", func: "_start" }
+    //   "#init" -> { path: "", func: "init" }
+    fn wasi_entrypoint(&self) -> WasiEntrypoint;
+}
+
+pub struct WasiEntrypoint {
+    pub path: PathBuf,
+    pub func: String,
+}
+
+impl RuntimeContext for Spec {
+    fn args(&self) -> &[String] {
+        self.process()
+            .as_ref()
+            .and_then(|p| p.args().as_ref())
+            .map(|a| a.as_slice())
+            .unwrap_or_default()
+    }
+
+    fn entrypoint(&self) -> Option<&Path> {
+        self.args().first().map(Path::new)
+    }
+
+    fn wasi_entrypoint(&self) -> WasiEntrypoint {
+        let arg0 = self.args().first().map(String::as_str).unwrap_or("");
+        let (path, func) = arg0.split_once('#').unwrap_or((arg0, "_start"));
+        WasiEntrypoint {
+            path: PathBuf::from(path),
+            func: func.to_string(),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use anyhow::Result;
+    use oci_spec::runtime::{ProcessBuilder, RootBuilder, SpecBuilder};
+
+    use super::*;
+
+    #[test]
+    fn test_get_args() -> Result<()> {
+        let spec = SpecBuilder::default()
+            .root(RootBuilder::default().path("rootfs").build()?)
+            .process(
+                ProcessBuilder::default()
+                    .cwd("/")
+                    .args(vec!["hello.wat".to_string()])
+                    .build()?,
+            )
+            .build()?;
+        let spec = &spec;
+
+        let args = spec.args();
+        assert_eq!(args.len(), 1);
+        assert_eq!(args[0], "hello.wat");
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_get_args_return_empty() -> Result<()> {
+        let spec = SpecBuilder::default()
+            .root(RootBuilder::default().path("rootfs").build()?)
+            .process(ProcessBuilder::default().cwd("/").args(vec![]).build()?)
+            .build()?;
+        let spec = &spec;
+
+        let args = spec.args();
+        assert_eq!(args.len(), 0);
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_get_args_returns_all() -> Result<()> {
+        let spec = SpecBuilder::default()
+            .root(RootBuilder::default().path("rootfs").build()?)
+            .process(
+                ProcessBuilder::default()
+                    .cwd("/")
+                    .args(vec![
+                        "hello.wat".to_string(),
+                        "echo".to_string(),
+                        "hello".to_string(),
+                    ])
+                    .build()?,
+            )
+            .build()?;
+        let spec = &spec;
+
+        let args = spec.args();
+        assert_eq!(args.len(), 3);
+        assert_eq!(args[0], "hello.wat");
+        assert_eq!(args[1], "echo");
+        assert_eq!(args[2], "hello");
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_get_module_returns_none_when_not_present() -> Result<()> {
+        let spec = SpecBuilder::default()
+            .root(RootBuilder::default().path("rootfs").build()?)
+            .process(ProcessBuilder::default().cwd("/").args(vec![]).build()?)
+            .build()?;
+        let spec = &spec;
+
+        let path = spec.wasi_entrypoint().path;
+        assert!(path.as_os_str().is_empty());
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_get_module_returns_function() -> Result<()> {
+        let spec = SpecBuilder::default()
+            .root(RootBuilder::default().path("rootfs").build()?)
+            .process(
+                ProcessBuilder::default()
+                    .cwd("/")
+                    .args(vec![
+                        "hello.wat#foo".to_string(),
+                        "echo".to_string(),
+                        "hello".to_string(),
+                    ])
+                    .build()?,
+            )
+            .build()?;
+        let spec = &spec;
+
+        let WasiEntrypoint { path, func } = spec.wasi_entrypoint();
+        assert_eq!(path, Path::new("hello.wat"));
+        assert_eq!(func, "foo");
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_get_module_returns_start() -> Result<()> {
+        let spec = SpecBuilder::default()
+            .root(RootBuilder::default().path("rootfs").build()?)
+            .process(
+                ProcessBuilder::default()
+                    .cwd("/")
+                    .args(vec![
+                        "/root/hello.wat".to_string(),
+                        "echo".to_string(),
+                        "hello".to_string(),
+                    ])
+                    .build()?,
+            )
+            .build()?;
+        let spec = &spec;
+
+        let WasiEntrypoint { path, func } = spec.wasi_entrypoint();
+        assert_eq!(path, Path::new("/root/hello.wat"));
+        assert_eq!(func, "_start");
+
+        Ok(())
+    }
+}

crates/containerd-shim-wasm/src/container/engine.rs

@@ -0,0 +1,39 @@
+use std::fs::File;
+use std::io::Read;
+
+use anyhow::{Context, Result};
+
+use crate::container::{PathResolve, RuntimeContext};
+use crate::sandbox::Stdio;
+
+pub trait Engine: Clone + Send + Sync + 'static {
+    /// The name to use for this engine
+    fn name() -> &'static str;
+
+    /// Run a WebAssembly container
+    fn run_wasi(&self, ctx: &impl RuntimeContext, stdio: Stdio) -> Result<i32>;
+
+    /// Check that the runtime can run the container.
+    /// This checks runs after the container creation and before the container starts.
+    /// By it checks that the wasi_entrypoint is either:
+    /// * a file with the `wasm` filetype header
+    /// * a parsable `wat` file.
+    fn can_handle(&self, ctx: &impl RuntimeContext) -> Result<()> {
+        let path = ctx
+            .wasi_entrypoint()
+            .path
+            .resolve_in_path_or_cwd()
+            .next()
+            .context("module not found")?;
+
+        let mut buffer = [0; 4];
+        File::open(&path)?.read_exact(&mut buffer)?;
+
+        if buffer.as_slice() != b"\0asm" {
+            // Check if this is a `.wat` file
+            wat::parse_file(&path)?;
+        }
+
+        Ok(())
+    }
+}