feat: add support for running a subset of app components

Signed-off-by: Kate Goldenring <[email protected]>

containerd-shim-spin/Cargo.toml

@@ -13,6 +13,7 @@ Containerd shim for running Spin workloads.
 [dependencies]
 containerd-shim-wasm = "0.6.0"
 containerd-shim = "0.7.1"
+http = "1"
 log = "0.4"
 spin-app = { git = "https://github.com/fermyon/spin", rev = "485b04090644ecfda4d0034891a5feca9a90332c" }
 spin-core = { git = "https://github.com/fermyon/spin", rev = "485b04090644ecfda4d0034891a5feca9a90332c" }
@@ -35,8 +36,9 @@ spin-factors-executor = { git = "https://github.com/fermyon/spin", rev = "485b04
 spin-telemetry = { git = "https://github.com/fermyon/spin", rev = "485b04090644ecfda4d0034891a5feca9a90332c" }
 spin-runtime-factors = { git = "https://github.com/fermyon/spin", rev = "485b04090644ecfda4d0034891a5feca9a90332c" }
 spin-factors = { git = "https://github.com/fermyon/spin", rev = "485b04090644ecfda4d0034891a5feca9a90332c" }
+spin-factor-outbound-networking = { git = "https://github.com/fermyon/spin", rev = "485b04090644ecfda4d0034891a5feca9a90332c" }
 wasmtime = "22.0"
-tokio = { version = "1.38", features = ["rt"] }
+tokio = { version = "1", features = ["rt"] }
 openssl = { version = "*", features = ["vendored"] }
 serde = "1.0"
 serde_json = "1.0"
@@ -49,3 +51,5 @@ ctrlc = { version = "3.4", features = ["termination"] }
 [dev-dependencies]
 wat = "1"
 temp-env = "0.3.6"
+toml = "0.8"
+tempfile = "3"

containerd-shim-spin/src/constants.rs

@@ -18,3 +18,6 @@ pub(crate) const SPIN_MANIFEST_FILE_PATH: &str = "/spin.toml";
 pub(crate) const SPIN_APPLICATION_VARIABLE_PREFIX: &str = "SPIN_VARIABLE";
 /// Working directory for Spin applications
 pub(crate) const SPIN_TRIGGER_WORKING_DIR: &str = "/";
+/// Defines the subset of application components that should be executable by the shim
+/// If empty or DNE, all components will be supported
+pub(crate) const SPIN_COMPONENTS_TO_RETAIN_ENV: &str = "SPIN_COMPONENTS_TO_RETAIN";

containerd-shim-spin/src/engine.rs

@@ -136,7 +136,13 @@ impl SpinEngine {
     async fn wasm_exec_async(&self, ctx: &impl RuntimeContext) -> Result<()> {
         let cache = initialize_cache().await?;
         let app_source = Source::from_ctx(ctx, &cache).await?;
-        let locked_app = app_source.to_locked_app(&cache).await?;
+        let mut locked_app = app_source.to_locked_app(&cache).await?;
+        let components_to_execute = env::var(constants::SPIN_COMPONENTS_TO_RETAIN_ENV)
+            .ok()
+            .map(|s| s.split(',').map(|s| s.to_string()).collect::<Vec<String>>());
+        if let Some(components) = components_to_execute {
+            crate::retain::retain_components(&mut locked_app, &components)?;
+        }
         configure_application_variables_from_environment_variables(&locked_app)?;
         let trigger_cmds = get_supported_triggers(&locked_app)
             .with_context(|| format!("Couldn't find trigger executor for {app_source:?}"))?;

containerd-shim-spin/src/main.rs

@@ -6,6 +6,7 @@ use containerd_shim_wasm::{
 
 mod constants;
 mod engine;
+mod retain;
 mod source;
 mod trigger;
 mod utils;

containerd-shim-spin/src/retain.rs

@@ -0,0 +1,241 @@
+//! This module contains the logic for modifying a locked app to only contain a subset of its components
+
+use std::collections::HashSet;
+
+use anyhow::{bail, Context, Result};
+use spin_app::locked::LockedApp;
+use spin_factor_outbound_networking::{allowed_outbound_hosts, parse_service_chaining_target};
+
+/// Scrubs the locked app to only contain the given list of components
+/// Introspects the LockedApp to find and selectively retain the triggers that correspond to those components
+pub fn retain_components(locked_app: &mut LockedApp, retained_components: &[String]) -> Result<()> {
+    // Create a temporary app to access parsed component and trigger information
+    let tmp_app = spin_app::App::new("tmp", locked_app.clone());
+    validate_retained_components_exist(&tmp_app, retained_components)?;
+    validate_retained_components_service_chaining(&tmp_app, retained_components)?;
+    let (component_ids, trigger_ids): (HashSet<String>, HashSet<String>) = tmp_app
+        .triggers()
+        .filter_map(|t| match t.component() {
+            Ok(comp) if retained_components.contains(&comp.id().to_string()) => {
+                Some((comp.id().to_owned(), t.id().to_owned()))
+            }
+            _ => None,
+        })
+        .collect();
+    locked_app
+        .components
+        .retain(|c| component_ids.contains(&c.id));
+    locked_app.triggers.retain(|t| trigger_ids.contains(&t.id));
+    Ok(())
+}
+
+// Validates that all service chaining of an app will be satisfied by the
+// retained components.
+//
+// This does a best effort look up of components that are
+// allowed to be accessed through service chaining and will error early if a
+// component is configured to to chain to another component that is not
+// retained. All wildcard service chaining is disallowed and all templated URLs
+// are ignored.
+fn validate_retained_components_service_chaining(
+    app: &spin_app::App,
+    retained_components: &[String],
+) -> Result<()> {
+    app
+        .triggers().try_for_each(|t| {
+            let Ok(component) = t.component() else  { return Ok(()) };
+            if retained_components.contains(&component.id().to_string()) {
+            let allowed_hosts = allowed_outbound_hosts(&component).context("failed to get allowed hosts")?;
+            for host in allowed_hosts {
+                // Templated URLs are not yet resolved at this point, so ignore unresolvable URIs
+                if let Ok(uri) = host.parse::<http::Uri>() {
+                    if let Some(chaining_target) = parse_service_chaining_target(&uri) {
+                        if !retained_components.contains(&chaining_target) {
+                            if chaining_target == "*" {
+                                bail!("Component selected with '--component {}' cannot use wildcard service chaining: allowed_outbound_hosts = [\"http://*.spin.internal\"]", component.id());
+                            }
+                            bail!(
+                                "Component selected with '--component {}' cannot use service chaining to unselected component: allowed_outbound_hosts = [\"http://{}.spin.internal\"]",
+                                component.id(), chaining_target
+                            );
+                        }
+                    }
+                }
+            }
+        }
+        anyhow::Ok(())
+    })?;
+
+    Ok(())
+}
+
+// Validates that all components specified to be retained actually exist in the app
+fn validate_retained_components_exist(
+    app: &spin_app::App,
+    retained_components: &[String],
+) -> Result<()> {
+    let app_components = app
+        .components()
+        .map(|c| c.id().to_string())
+        .collect::<HashSet<_>>();
+    for c in retained_components {
+        if !app_components.contains(c) {
+            bail!("Specified component \"{c}\" not found in application");
+        }
+    }
+    Ok(())
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    pub async fn build_locked_app(
+        manifest: &toml::map::Map<String, toml::Value>,
+    ) -> anyhow::Result<LockedApp> {
+        let toml_str = toml::to_string(manifest).context("failed serializing manifest")?;
+        let dir = tempfile::tempdir().context("failed creating tempdir")?;
+        let path = dir.path().join("spin.toml");
+        std::fs::write(&path, toml_str).context("failed writing manifest")?;
+        spin_loader::from_file(&path, spin_loader::FilesMountStrategy::Direct, None).await
+    }
+
+    #[tokio::test]
+    async fn test_retain_components_filtering_for_only_component_works() {
+        let manifest = toml::toml! {
+            spin_manifest_version = 2
+
+            [application]
+            name = "test-app"
+
+            [[trigger.test-trigger]]
+            component = "empty"
+
+            [component.empty]
+            source = "does-not-exist.wasm"
+        };
+        let mut locked_app = build_locked_app(&manifest).await.unwrap();
+        retain_components(&mut locked_app, &["empty".to_string()]).unwrap();
+        let components = locked_app
+            .components
+            .iter()
+            .map(|c| c.id.to_string())
+            .collect::<HashSet<_>>();
+        assert!(components.contains("empty"));
+        assert!(components.len() == 1);
+    }
+
+    #[tokio::test]
+    async fn test_retain_components_filtering_for_non_existent_component_fails() {
+        let manifest = toml::toml! {
+            spin_manifest_version = 2
+
+            [application]
+            name = "test-app"
+
+            [[trigger.test-trigger]]
+            component = "empty"
+
+            [component.empty]
+            source = "does-not-exist.wasm"
+        };
+        let mut locked_app = build_locked_app(&manifest).await.unwrap();
+        let Err(e) = retain_components(&mut locked_app, &["dne".to_string()]) else {
+            panic!("Expected component not found error");
+        };
+        assert_eq!(
+            e.to_string(),
+            "Specified component \"dne\" not found in application"
+        );
+        assert!(retain_components(&mut locked_app, &["dne".to_string()]).is_err());
+    }
+
+    #[tokio::test]
+    async fn test_retain_components_app_with_service_chaining_fails() {
+        let manifest = toml::toml! {
+            spin_manifest_version = 2
+
+            [application]
+            name = "test-app"
+
+            [[trigger.test-trigger]]
+            component = "empty"
+
+            [component.empty]
+            source = "does-not-exist.wasm"
+            allowed_outbound_hosts = ["http://another.spin.internal"]
+
+            [[trigger.another-trigger]]
+            component = "another"
+
+            [component.another]
+            source = "does-not-exist.wasm"
+
+            [[trigger.third-trigger]]
+            component = "third"
+
+            [component.third]
+            source = "does-not-exist.wasm"
+            allowed_outbound_hosts = ["http://*.spin.internal"]
+        };
+        let mut locked_app = build_locked_app(&manifest)
+            .await
+            .expect("could not build locked app");
+        let Err(e) = retain_components(&mut locked_app, &["empty".to_string()]) else {
+            panic!("Expected service chaining to non-retained component error");
+        };
+        assert_eq!(
+            e.to_string(),
+            "Component selected with '--component empty' cannot use service chaining to unselected component: allowed_outbound_hosts = [\"http://another.spin.internal\"]"
+        );
+        let Err(e) = retain_components(
+            &mut locked_app,
+            &["third".to_string(), "another".to_string()],
+        ) else {
+            panic!("Expected wildcard service chaining error");
+        };
+        assert_eq!(
+            e.to_string(),
+            "Component selected with '--component third' cannot use wildcard service chaining: allowed_outbound_hosts = [\"http://*.spin.internal\"]"
+        );
+        assert!(retain_components(&mut locked_app, &["another".to_string()]).is_ok());
+    }
+
+    #[tokio::test]
+    async fn test_retain_components_app_with_templated_host_passes() {
+        let manifest = toml::toml! {
+            spin_manifest_version = 2
+
+            [application]
+            name = "test-app"
+
+            [variables]
+            host = { default = "test" }
+
+            [[trigger.test-trigger]]
+            component = "empty"
+
+            [component.empty]
+            source = "does-not-exist.wasm"
+
+            [[trigger.another-trigger]]
+            component = "another"
+
+            [component.another]
+            source = "does-not-exist.wasm"
+
+            [[trigger.third-trigger]]
+            component = "third"
+
+            [component.third]
+            source = "does-not-exist.wasm"
+            allowed_outbound_hosts = ["http://{{ host }}.spin.internal"]
+        };
+        let mut locked_app = build_locked_app(&manifest)
+            .await
+            .expect("could not build locked app");
+        assert!(
+            retain_components(&mut locked_app, &["empty".to_string(), "third".to_string()]).is_ok()
+        );
+    }
+}