cleanup(kernel): undo some kernel changes

As mentioned in
https://github.com/extism/extism/pull/696/files#r1993086470, the key
parameter doesnt seem very useful. You can achieve the same effect by
doing `HashMap<Key, PluginPool>` in the client code.

---------

Co-authored-by: zach <zach@dylibso.com>

.github/dependabot.yml

@@ -9,12 +9,8 @@ updates:
     directory: "/" # Location of package manifests
     schedule:
       interval: "weekly"
-    groups:
-      # This is the name of your group, it will be used in PR titles and branch names
-      wasmtime-deps:
-        # A pattern can be...
-        patterns:
-          - "wasmtime"
-          - "wasi-common"
-          - "wiggle"
+    ignore:
+      - dependency-name: "wasmtime"
+      - dependency-name: "wasi-common"
+      - dependency-name: "wiggle"
 

.github/workflows/release-dotnet-native.yaml

@@ -20,10 +20,13 @@ jobs:
         uses: actions/setup-dotnet@v3.0.3
         with:
            dotnet-version: 7.x
-      - uses: dawidd6/action-download-artifact@v6
-        with:
-          workflow: release.yml
-          name: release-artifacts
+      - name: download release
+        run: |
+          tag='${{ github.ref }}'
+          tag="${tag/refs\/tags\//}"
+          gh release download "$tag" -p 'libextism-*.tar.gz'
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       - name: Extract Archive
         run: |      
           extract_archive() {

convert-macros/src/lib.rs

@@ -34,11 +34,11 @@ fn extract_encoding(attrs: &[Attribute]) -> Result<Path> {
         .iter()
         .filter(|attr| attr.path().is_ident("encoding"))
         .collect();
-    ensure!(!encodings.is_empty(), "encoding needs to be specified"; try = "`#[encoding(ToJson)]`");
+    ensure!(!encodings.is_empty(), "encoding needs to be specified"; try = "`#[encoding(Json)]`");
     ensure!(encodings.len() < 2, encodings[1], "only one encoding can be specified"; try = "remove `{}`", encodings[1].to_token_stream());
 
     Ok(encodings[0].parse_args().map_err(
-        |e| error_message!(e.span(), "{e}"; note= "expects a path"; try = "`#[encoding(ToJson)]`"),
+        |e| error_message!(e.span(), "{e}"; note= "expects a path"; try = "`#[encoding(Json)]`"),
     )?)
 }
 

convert-macros/tests/ui/invalid-encoding.stderr

@@ -1,6 +1,6 @@
 error: encoding needs to be specified
 
-         = try: `#[encoding(ToJson)]`
+         = try: `#[encoding(Json)]`
  --> tests/ui/invalid-encoding.rs:3:10
   |
 3 | #[derive(ToBytes)]
@@ -11,7 +11,7 @@ error: encoding needs to be specified
 error: expected attribute arguments in parentheses: #[encoding(...)]
 
          = note: expects a path
-         = try: `#[encoding(ToJson)]`
+         = try: `#[encoding(Json)]`
  --> tests/ui/invalid-encoding.rs:7:3
   |
 7 | #[encoding]
@@ -20,7 +20,7 @@ error: expected attribute arguments in parentheses: #[encoding(...)]
 error: expected parentheses: #[encoding(...)]
 
          = note: expects a path
-         = try: `#[encoding(ToJson)]`
+         = try: `#[encoding(Json)]`
   --> tests/ui/invalid-encoding.rs:11:12
    |
 11 | #[encoding = "string"]
@@ -29,7 +29,7 @@ error: expected parentheses: #[encoding(...)]
 error: unexpected token
 
          = note: expects a path
-         = try: `#[encoding(ToJson)]`
+         = try: `#[encoding(Json)]`
   --> tests/ui/invalid-encoding.rs:15:21
    |
 15 | #[encoding(something, else)]

convert/src/from_bytes.rs

@@ -141,6 +141,16 @@ impl FromBytesOwned for u32 {
     }
 }
 
+impl FromBytesOwned for bool {
+    fn from_bytes_owned(data: &[u8]) -> Result<Self, Error> {
+        if let Some(x) = data.first() {
+            Ok(*x != 0)
+        } else {
+            Err(Error::msg("Expected one byte to read boolean value"))
+        }
+    }
+}
+
 impl FromBytesOwned for () {
     fn from_bytes_owned(_: &[u8]) -> Result<Self, Error> {
         Ok(())

convert/src/tests.rs

@@ -61,6 +61,17 @@ fn rountrip_option() {
     assert_eq!(y.unwrap().0, z.unwrap().0);
 }
 
+#[test]
+fn check_bool() {
+    // `None` case
+    let a = true.to_bytes().unwrap();
+    let b = false.to_bytes().unwrap();
+    assert_ne!(a, b);
+
+    assert_eq!(a, [1]);
+    assert_eq!(b, [0]);
+}
+
 #[cfg(all(feature = "raw", target_endian = "little"))]
 mod raw_tests {
     use crate::*;

convert/src/to_bytes.rs

@@ -144,6 +144,14 @@ impl ToBytes<'_> for u32 {
     }
 }
 
+impl ToBytes<'_> for bool {
+    type Bytes = [u8; 1];
+
+    fn to_bytes(&self) -> Result<Self::Bytes, Error> {
+        Ok([*self as u8])
+    }
+}
+
 impl<'a, T: ToBytes<'a>> ToBytes<'a> for &'a T {
     type Bytes = T::Bytes;
 

runtime/Cargo.toml

@@ -34,10 +34,10 @@ register-filesystem = [] # enables wasm to be loaded from disk
 http = ["ureq"]          # enables extism_http_request
 
 [build-dependencies]
-cbindgen = { version = "0.28", default-features = false }
+cbindgen = { version = "0.29", default-features = false }
 
 [dev-dependencies]
-criterion = "0.5.1"
+criterion = "0.6.0"
 quickcheck = "1"
 rand = "0.9.0"
 

runtime/README.md

@@ -24,7 +24,7 @@ There are a few environment variables that can be used for debugging purposes:
 - `EXTISM_COREDUMP=extism.core`: write [coredump](https://github.com/WebAssembly/tool-conventions/blob/main/Coredump.md) to a file when a WebAssembly function traps
 - `EXTISM_DEBUG=1`: generate debug information
 - `EXTISM_PROFILE=perf|jitdump|vtune`: enable Wasmtime profiling
-- `EXTISM_CACHE_CONFIG=path/to/config.toml`: enable Wasmtime cache, see [the docs](https://docs.wasmtime.dev/cli-cache.html) for details about configuration. Setting this to an empty string will disable caching.
+- `EXTISM_CACHE_CONFIG=path/to/config.toml`: enable Wasmtime cache, details [here](#wasmtime-caching)
 
 > *Note*: The debug and coredump info will only be written if the plug-in has an error.
 
@@ -229,3 +229,42 @@ Inside your host application, the rust-sdk emits these as [tracing](https://gith
 tracing_subscriber::fmt::init();
 ```
 
+### Wasmtime Caching
+
+To enable or disable caching for plugin compilation, you need to provide a configuration file that will be used by the [wasmtime crate](https://github.com/bytecodealliance/wasmtime).
+
+For more information and values that can be used for configuring caching, take a look at [the docs](https://docs.wasmtime.dev/cli-cache.html).
+
+> *Note*: As of now extism uses wasmtime [`version = ">= 27.0.0, < 31.0.0"`](https://github.com/extism/extism/blob/v1.11.1/runtime/Cargo.toml#L12), but the `enabled` key requirement [was removed](https://github.com/bytecodealliance/wasmtime/pull/10859) from `wasmtime` and its documentation, this could explain the `failed to parse config file` error you might encounter without it.
+
+An example configuration for caching would be:
+
+```toml
+[cache]
+enabled = true # This value is required
+directory = "/some/path"
+```
+
+You can :
+- [Create a global `wasmtime` configuration file](#using-a-configuration-file) in `$HOME/.config/wasmtime/config.toml`.
+- [Set the `EXTISM_CACHE_CONFIG` environment variable](#using-an-environment-variable)
+- [Set the configuration file path using `PluginBuilder`](#using-pluginbuilder)
+
+#### Using a configuration file
+
+The [wasmtime](https://github.com/bytecodealliance/wasmtime) crate, by default, will look for a configuration file in your systems' default configuration directory (for example on UNIX systems: `$HOME/.config/wasmtime/config.toml`),
+for more [information on this behaviour](`https://docs.rs/wasmtime/31.0.0/wasmtime/struct.Config.html#method.cache_config_load_default`).
+
+#### Using an environment variable
+
+You can set the `EXTISM_CACHE_CONFIG=path/to/config.toml` environment variable to set the path of the configuration file used by [wasmtime](https://github.com/bytecodealliance/wasmtime).
+Setting the variable to an empty string will disable caching (it won't load any configuration file).
+
+> *Note*: If the environment variable is not set, `wasmtime` will still try to read from a configuration file that may exist in your system's default configuration folder (e.g. `$HOME/.config/wasmtime/config.toml`).
+
+The environment variable does not override the path you might have set using `PluginBuilder`. will only be checked for if you did not specify a cache configuration path in `PluginBuilder`.
+
+#### Using PluginBuilder
+
+If you use a [PluginBuilder](https://docs.rs/extism/latest/extism/struct.PluginBuilder.html), you can set the `wasmtime` configuration path using the [with_cache_config](https://docs.rs/extism/latest/extism/struct.PluginBuilder.html#method.with_cache_config) method.
+This will override the `EXTISM_CACHE_CONFIG` environment variable if it's set, so you could have a "global" and per plugin configuration if needed.

runtime/examples/fs.rs

@@ -16,7 +16,7 @@ fn main() {
 
     let res = plugin.call::<&str, &str>("try_read", "").unwrap();
 
-    println!("{:?}", res);
+    println!("{res:?}");
 
     println!("-----------------------------------------------------");
 
@@ -30,7 +30,7 @@ fn main() {
     );
     let res2 = plugin.call::<&str, &str>("try_write", &line).unwrap();
 
-    println!("{:?}", res2);
+    println!("{res2:?}");
 
     println!("done!");
 }

runtime/examples/linking.rs

@@ -30,6 +30,6 @@ fn main() {
         let res = plugin
             .call::<&str, &str>("reflect", "Hello, world!")
             .unwrap();
-        println!("{}", res);
+        println!("{res}");
     }
 }

runtime/examples/log_callback.rs

@@ -25,6 +25,6 @@ fn main() {
     println!("Dumping logs");
 
     for line in LOGS.lock().unwrap().iter() {
-        print!("{}", line);
+        print!("{line}");
     }
 }

runtime/examples/readme.rs

@@ -52,6 +52,6 @@ fn main() {
         let res = plugin
             .call::<&str, &str>("count_vowels", "Hello, world!")
             .unwrap();
-        println!("{}", res);
+        println!("{res}");
     }
 }

runtime/extism.h

@@ -156,7 +156,7 @@ void extism_current_plugin_memory_free(ExtismCurrentPlugin *plugin, ExtismMemory
  * - `n_outputs`: number of return types
  * - `func`: the function to call
  * - `user_data`: a pointer that will be passed to the function when it's called
- *    this value should live as long as the function exists
+ *   this value should live as long as the function exists
  * - `free_user_data`: a callback to release the `user_data` value when the resulting
  *   `ExtismFunction` is freed.
  *

runtime/src/current_plugin.rs

@@ -477,10 +477,7 @@ impl CurrentPlugin {
             offset: offs,
             length,
         });
-        match s {
-            Ok(s) => Some(s),
-            Err(_) => None,
-        }
+        s.ok()
     }
 
     #[doc(hidden)]

runtime/src/function.rs

@@ -284,8 +284,8 @@ impl Function {
 /// A few things worth noting:
 /// - The function always returns a `Result` that wraps the specified return type
 /// - If a first parameter and type are passed (`_user_data` above) followed by a semicolon it will be
-///    the name of the `UserData` parameter and can be used from inside the function
-//     definition.
+///   the name of the `UserData` parameter and can be used from inside the function
+//    definition.
 #[macro_export]
 macro_rules! host_fn {
     ($pub:vis $name: ident  ($($arg:ident : $argty:ty),*) $(-> $ret:ty)? $b:block) => {

runtime/src/lib.rs

@@ -29,6 +29,7 @@ pub(crate) mod manifest;
 pub(crate) mod pdk;
 mod plugin;
 mod plugin_builder;
+mod pool;
 mod readonly_dir;
 mod timer;
 
@@ -43,6 +44,7 @@ pub use plugin::{
     CancelHandle, CompiledPlugin, Plugin, WasmInput, EXTISM_ENV_MODULE, EXTISM_USER_MODULE,
 };
 pub use plugin_builder::{DebugOptions, PluginBuilder};
+pub use pool::{Pool, PoolBuilder, PoolPlugin};
 
 pub(crate) use internal::{Internal, Wasi};
 pub(crate) use timer::{Timer, TimerAction};
@@ -96,7 +98,7 @@ pub fn set_log_callback<F: 'static + Clone + Fn(&str)>(
         let x = tracing_subscriber::EnvFilter::builder()
             .with_default_directive(tracing::Level::ERROR.into());
         if is_level {
-            x.parse_lossy(format!("extism={}", filter))
+            x.parse_lossy(format!("extism={filter}"))
         } else {
             x.parse_lossy(filter)
         }

runtime/src/manifest.rs

@@ -10,7 +10,7 @@ use crate::*;
 fn hex(data: &[u8]) -> String {
     let mut s = String::new();
     for &byte in data {
-        write!(&mut s, "{:02x}", byte).unwrap();
+        write!(&mut s, "{byte:02x}").unwrap();
     }
     s
 }

runtime/src/plugin.rs

@@ -191,6 +191,7 @@ pub(crate) fn profiling_strategy() -> ProfilingStrategy {
 /// Defines an input type for Wasm data.
 ///
 /// Types that implement `Into<WasmInput>` can be passed directly into `Plugin::new`
+#[derive(Clone)]
 pub enum WasmInput<'a> {
     /// Raw Wasm module
     Data(std::borrow::Cow<'a, [u8]>),
@@ -962,8 +963,7 @@ impl Plugin {
                     }
                     Err(msg) => {
                         res = Err(Error::msg(format!(
-                            "unable to load error message from memory: {}",
-                            msg,
+                            "unable to load error message from memory: {msg}",
                         )));
                     }
                 }

runtime/src/plugin_builder.rs

@@ -33,6 +33,7 @@ impl Default for DebugOptions {
 }
 
 /// PluginBuilder is used to configure and create `Plugin` instances
+#[derive(Clone)]
 pub struct PluginBuilder<'a> {
     pub(crate) source: WasmInput<'a>,
     pub(crate) config: Option<wasmtime::Config>,

runtime/src/pool.rs

@@ -0,0 +1,174 @@
+use crate::{Error, FromBytesOwned, Plugin, ToBytes};
+
+// `PoolBuilder` is used to configure and create `Pool`s
+#[derive(Debug, Clone)]
+pub struct PoolBuilder {
+    /// Max number of concurrent instances for a plugin - by default this is set to
+    /// the output of `std::thread::available_parallelism`
+    pub max_instances: usize,
+}
+
+impl PoolBuilder {
+    /// Create a `PoolBuilder` with default values
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Set the max number of parallel instances
+    pub fn with_max_instances(mut self, n: usize) -> Self {
+        self.max_instances = n;
+        self
+    }
+
+    /// Create a new `Pool` with the given configuration
+    pub fn build<F: 'static + Fn() -> Result<Plugin, Error>>(self, source: F) -> Pool {
+        Pool::new_from_builder(source, self)
+    }
+}
+
+impl Default for PoolBuilder {
+    fn default() -> Self {
+        PoolBuilder {
+            max_instances: std::thread::available_parallelism()
+                .expect("available parallelism")
+                .into(),
+        }
+    }
+}
+
+/// `PoolPlugin` is used by the pool to track the number of live instances of a particular plugin
+#[derive(Clone, Debug)]
+pub struct PoolPlugin(std::rc::Rc<std::cell::RefCell<Plugin>>);
+
+impl PoolPlugin {
+    fn new(plugin: Plugin) -> Self {
+        Self(std::rc::Rc::new(std::cell::RefCell::new(plugin)))
+    }
+
+    /// Access the underlying plugin
+    pub fn plugin(&self) -> std::cell::RefMut<Plugin> {
+        self.0.borrow_mut()
+    }
+
+    /// Helper to call a plugin function on the underlying plugin
+    pub fn call<'a, Input: ToBytes<'a>, Output: FromBytesOwned>(
+        &self,
+        name: impl AsRef<str>,
+        input: Input,
+    ) -> Result<Output, Error> {
+        self.plugin().call(name.as_ref(), input)
+    }
+
+    /// Helper to get the underlying plugin's ID
+    pub fn id(&self) -> uuid::Uuid {
+        self.plugin().id
+    }
+}
+
+type PluginSource = dyn Fn() -> Result<Plugin, Error>;
+
+struct PoolInner {
+    plugin_source: Box<PluginSource>,
+    instances: Vec<PoolPlugin>,
+}
+
+unsafe impl Send for PoolInner {}
+unsafe impl Sync for PoolInner {}
+
+/// `Pool` manages threadsafe access to a limited number of instances of multiple plugins
+#[derive(Clone)]
+pub struct Pool {
+    config: PoolBuilder,
+    inner: std::sync::Arc<std::sync::Mutex<PoolInner>>,
+}
+
+unsafe impl Send for Pool {}
+unsafe impl Sync for Pool {}
+
+impl Pool {
+    /// Create a new pool with the default configuration
+    pub fn new<F: 'static + Fn() -> Result<Plugin, Error>>(source: F) -> Self {
+        Pool {
+            config: Default::default(),
+            inner: std::sync::Arc::new(std::sync::Mutex::new(PoolInner {
+                plugin_source: Box::new(source),
+                instances: Default::default(),
+            })),
+        }
+    }
+
+    /// Create a new pool configured using a `PoolBuilder`
+    pub fn new_from_builder<F: 'static + Fn() -> Result<Plugin, Error>>(
+        source: F,
+        builder: PoolBuilder,
+    ) -> Self {
+        Pool {
+            config: builder,
+            inner: std::sync::Arc::new(std::sync::Mutex::new(PoolInner {
+                plugin_source: Box::new(source),
+                instances: Default::default(),
+            })),
+        }
+    }
+
+    fn find_available(&self) -> Result<Option<PoolPlugin>, Error> {
+        let pool = self.inner.lock().unwrap();
+        for instance in pool.instances.iter() {
+            if std::rc::Rc::strong_count(&instance.0) == 1 {
+                return Ok(Some(instance.clone()));
+            }
+        }
+        Ok(None)
+    }
+
+    /// Get the number of live instances for a plugin
+    pub fn count(&self) -> usize {
+        self.inner.lock().unwrap().instances.len()
+    }
+
+    /// Get access to a plugin, this will create a new instance if needed (and allowed by the specified
+    /// max_instances). `Ok(None)` is returned if the timeout is reached before an available plugin could be
+    /// acquired
+    pub fn get(&self, timeout: std::time::Duration) -> Result<Option<PoolPlugin>, Error> {
+        let start = std::time::Instant::now();
+        let max = self.config.max_instances;
+        if let Some(avail) = self.find_available()? {
+            return Ok(Some(avail));
+        }
+
+        {
+            let mut pool = self.inner.lock().unwrap();
+            if pool.instances.len() < max {
+                let plugin = (*pool.plugin_source)()?;
+                let instance = PoolPlugin::new(plugin);
+                pool.instances.push(instance);
+                return Ok(Some(pool.instances.last().unwrap().clone()));
+            }
+        }
+
+        loop {
+            if let Ok(Some(x)) = self.find_available() {
+                return Ok(Some(x));
+            }
+            if std::time::Instant::now() - start > timeout {
+                return Ok(None);
+            }
+
+            std::thread::sleep(std::time::Duration::from_millis(100));
+        }
+    }
+
+    /// Access a plugin in a callback function. This calls `Pool::get` then the provided
+    /// callback. `Ok(None)` is returned if the timeout is reached before an available
+    /// plugin could be acquired
+    pub fn with_plugin<T>(
+        &self,
+        timeout: std::time::Duration,
+        f: impl FnOnce(&mut Plugin) -> Result<T, Error>,
+    ) -> Result<Option<T>, Error> {
+        if let Some(plugin) = self.get(timeout)? {
+            return f(&mut plugin.plugin()).map(Some);
+        }
+        Ok(None)
+    }
+}

runtime/src/sdk.rs

@@ -180,7 +180,7 @@ pub unsafe extern "C" fn extism_current_plugin_memory_free(
 /// - `n_outputs`: number of return types
 /// - `func`: the function to call
 /// - `user_data`: a pointer that will be passed to the function when it's called
-///    this value should live as long as the function exists
+///   this value should live as long as the function exists
 /// - `free_user_data`: a callback to release the `user_data` value when the resulting
 ///   `ExtismFunction` is freed.
 ///
@@ -871,7 +871,7 @@ fn set_log_file(log_file: impl Into<std::path::PathBuf>, filter: &str) -> Result
         let x = tracing_subscriber::EnvFilter::builder()
             .with_default_directive(tracing::Level::ERROR.into());
         if is_level {
-            x.parse_lossy(format!("extism={}", filter))
+            x.parse_lossy(format!("extism={filter}"))
         } else {
             x.parse_lossy(filter)
         }
@@ -926,7 +926,7 @@ unsafe fn set_log_buffer(filter: &str) -> Result<(), Error> {
         let x = tracing_subscriber::EnvFilter::builder()
             .with_default_directive(tracing::Level::ERROR.into());
         if is_level {
-            x.parse_lossy(format!("extism={}", filter))
+            x.parse_lossy(format!("extism={filter}"))
         } else {
             x.parse_lossy(filter)
         }

runtime/src/tests/issues.rs

@@ -16,7 +16,7 @@ fn test_issue_620() {
     // Call test method, this does not work
     let p = plugin.call::<(), String>("test", ()).unwrap();
 
-    println!("{}", p);
+    println!("{p}");
 }
 
 // https://github.com/extism/extism/issues/619
@@ -53,5 +53,5 @@ fn test_issue_775() {
         Ok(code) => Err(code),
     }
     .unwrap();
-    println!("{}", p);
+    println!("{p}");
 }

runtime/src/tests/kernel.rs

@@ -225,6 +225,26 @@ fn test_kernel_allocations() {
     extism_free(&mut store, instance, q);
 }
 
+#[test]
+fn test_kernel_page_allocations() {
+    let (mut store, mut instance) = init_kernel_test();
+    let instance = &mut instance;
+
+    let a = extism_alloc(&mut store, instance, 65500 * 4);
+    let a_size = extism_length(&mut store, instance, a);
+    let b = extism_alloc(&mut store, instance, 65539);
+
+    extism_free(&mut store, instance, a);
+    let c = extism_alloc(&mut store, instance, 65500 * 2);
+    let c_size = extism_length(&mut store, instance, c);
+
+    let d = extism_alloc(&mut store, instance, 65536);
+
+    assert_eq!(a + (a_size - c_size), c);
+    assert!(c < b);
+    assert!(d < b);
+}
+
 #[test]
 fn test_kernel_error() {
     let (mut store, mut instance) = init_kernel_test();
@@ -436,3 +456,32 @@ quickcheck! {
         true
     }
 }
+
+quickcheck! {
+    fn check_block_reuse(allocs: Vec<u16>) -> bool {
+        let (mut store, mut instance) = init_kernel_test();
+        let instance = &mut instance;
+        let init = extism_alloc(&mut store, instance, allocs.iter().map(|x| *x as u64).sum::<u64>() + (allocs.len() as u64 * (65535 + 128)));
+        let bounds = init + extism_length(&mut store, instance, init);
+        extism_free(&mut store, instance, init);
+        for a in allocs {
+            let ptr = extism_alloc(&mut store, instance, a as u64 + 65535);
+            if ptr == 0 {
+                continue
+            }
+            if extism_length(&mut store, instance, ptr) != a as u64 + 65535  {
+                println!("FAILED ALLOC");
+                return false
+            }
+
+            extism_free(&mut store, instance, ptr);
+
+            if ptr > bounds {
+                println!("ptr={ptr}, bounds={bounds}");
+                return false
+            }
+        }
+
+        true
+    }
+}

runtime/src/tests/mod.rs

@@ -1,3 +1,4 @@
 mod issues;
 mod kernel;
+mod pool;
 mod runtime;

runtime/src/tests/pool.rs

@@ -0,0 +1,48 @@
+use crate::*;
+
+fn run_thread(p: Pool, i: u64) -> std::thread::JoinHandle<()> {
+    std::thread::spawn(move || {
+        std::thread::sleep(std::time::Duration::from_millis(i));
+        let s: String = p
+            .get(std::time::Duration::from_secs(1))
+            .unwrap()
+            .unwrap()
+            .call("count_vowels", "abc")
+            .unwrap();
+        println!("{s}");
+    })
+}
+
+#[test]
+fn test_threads() {
+    for i in 1..=3 {
+        let data = include_bytes!("../../../wasm/code.wasm");
+        let plugin_builder =
+            extism::PluginBuilder::new(extism::Manifest::new([extism::Wasm::data(data)]))
+                .with_wasi(true);
+        let pool: Pool = PoolBuilder::new()
+            .with_max_instances(i)
+            .build(move || plugin_builder.clone().build());
+
+        let threads = vec![
+            run_thread(pool.clone(), 1000),
+            run_thread(pool.clone(), 1000),
+            run_thread(pool.clone(), 1000),
+            run_thread(pool.clone(), 1000),
+            run_thread(pool.clone(), 1000),
+            run_thread(pool.clone(), 1000),
+            run_thread(pool.clone(), 500),
+            run_thread(pool.clone(), 500),
+            run_thread(pool.clone(), 500),
+            run_thread(pool.clone(), 500),
+            run_thread(pool.clone(), 500),
+            run_thread(pool.clone(), 0),
+        ];
+
+        for t in threads {
+            t.join().unwrap();
+        }
+
+        assert!(pool.count() <= i);
+    }
+}

runtime/src/tests/runtime.rs

@@ -133,10 +133,7 @@ fn it_works() {
         .unwrap();
     let native_avg: std::time::Duration = native_sum / native_num_tests as u32;
 
-    println!(
-        "native function call (avg, N = {}): {:?}",
-        native_num_tests, native_avg
-    );
+    println!("native function call (avg, N = {native_num_tests}): {native_avg:?}");
 
     let num_tests = test_times.len();
     let sum: std::time::Duration = test_times
@@ -145,7 +142,7 @@ fn it_works() {
         .unwrap();
     let avg: std::time::Duration = sum / num_tests as u32;
 
-    println!("wasm function call (avg, N = {}): {:?}", num_tests, avg);
+    println!("wasm function call (avg, N = {num_tests}): {avg:?}");
 
     // Check that log file was written to
     if log {
@@ -212,7 +209,7 @@ fn test_cancel() {
         let _output: Result<&[u8], Error> = plugin.call("loop_forever", "abc123");
         let end = std::time::Instant::now();
         let time = end - start;
-        println!("Cancelled plugin ran for {:?}", time);
+        println!("Cancelled plugin ran for {time:?}");
     }
 }
 
@@ -271,7 +268,7 @@ fn test_fuel_consumption() {
     assert!(output.is_err());
 
     let fuel_consumed = plugin.fuel_consumed().unwrap();
-    println!("Fuel consumed: {}", fuel_consumed);
+    println!("Fuel consumed: {fuel_consumed}");
     assert!(fuel_consumed > 0);
 }
 
@@ -440,7 +437,7 @@ fn test_memory_max() {
     assert!(output.is_err());
 
     let err = output.unwrap_err().root_cause().to_string();
-    println!("{:?}", err);
+    println!("{err:?}");
     assert_eq!(err, "oom");
 
     // Should pass with memory.max set to a large enough number
@@ -503,7 +500,7 @@ fn test_extism_error() {
     let mut plugin = Plugin::new(&manifest, [f], true).unwrap();
     let output: Result<String, Error> = plugin.call("count_vowels", "a".repeat(1024));
     assert!(output.is_err());
-    println!("{:?}", output);
+    println!("{output:?}");
     assert_eq!(output.unwrap_err().root_cause().to_string(), "TEST");
 }
 
@@ -823,7 +820,7 @@ fn test_http_response_headers() {
     .unwrap();
     let req = HttpRequest::new("https://extism.org");
     let Json(res): Json<HashMap<String, String>> = plugin.call("http_get", Json(req)).unwrap();
-    println!("{:?}", res);
+    println!("{res:?}");
     assert_eq!(res["content-type"], "text/html; charset=utf-8");
 }
 
@@ -838,6 +835,6 @@ fn test_http_response_headers_disabled() {
     .unwrap();
     let req = HttpRequest::new("https://extism.org");
     let Json(res): Json<HashMap<String, String>> = plugin.call("http_get", Json(req)).unwrap();
-    println!("{:?}", res);
+    println!("{res:?}");
     assert!(res.is_empty());
 }