refactor: reinstate module cache

CHANGELOG.md

@@ -2,6 +2,11 @@
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+- **BREAKING CHANGE:** Instance cache in host crate has been removed in favor of a deserialized module cache `DeserializedModuleCache`. An abstraction for caching (serialized & deserialized modules) called `ModuleCache` was added.
+- Refactor: All logic related to modules and wasmer caching from `holochain` has been moved to the host crate. Consequently functions for wasmer development under iOS need to be imported from there.
+
 ## [0.0.90]
 
 - Bump wasmer to 4.2.4

Cargo.toml

@@ -1,3 +1,5 @@
 [workspace]
 members = ["crates/host", "crates/common"]
 exclude = ["test"]
+
+resolver = "2"

crates/host/src/module.rs

@@ -6,19 +6,30 @@ use bytes::Bytes;
 use bytes::BytesMut;
 use holochain_wasmer_common::WasmError;
 use parking_lot::Mutex;
+use parking_lot::RwLock;
 use std::collections::BTreeMap;
 use std::fs::File;
 use std::fs::OpenOptions;
 use std::io::Write;
 use std::path::PathBuf;
+use std::str::FromStr;
 use std::sync::Arc;
+use tracing::info;
+use wasmer::wasmparser;
 use wasmer::BaseTunables;
+use wasmer::CompileError;
+use wasmer::CompilerConfig;
+use wasmer::CpuFeature;
 use wasmer::Cranelift;
+use wasmer::DeserializeError;
 use wasmer::Engine;
 use wasmer::Instance;
 use wasmer::Module;
 use wasmer::NativeEngineExt;
 use wasmer::Store;
+use wasmer::Target;
+use wasmer::Triple;
+use wasmer_middlewares::Metering;
 
 /// We expect cache keys to be produced via hashing so 32 bytes is enough for all
 /// purposes.
@@ -119,6 +130,60 @@ pub trait PlruCache {
     }
 }
 
+#[cfg(not(test))]
+/// one hundred giga ops
+pub const WASM_METERING_LIMIT: u64 = 100_000_000_000;
+
+#[cfg(test)]
+/// ten mega ops.
+/// We don't want tests to run forever, and it can take several minutes for 100 giga ops to run.
+pub const WASM_METERING_LIMIT: u64 = 10_000_000;
+
+/// Generate an engine with a wasm compiler
+/// and Metering (use limits) in place.
+pub fn make_compiler_engine() -> Engine {
+    let cost_function = |_operator: &wasmparser::Operator| -> u64 { 1 };
+    // @todo 100 giga-ops is totally arbitrary cutoff so we probably
+    // want to make the limit configurable somehow.
+    let metering = Arc::new(Metering::new(WASM_METERING_LIMIT, cost_function));
+    // the only place where the wasm compiler engine is set
+    let mut compiler = Cranelift::default();
+    compiler.canonicalize_nans(true).push_middleware(metering);
+    Engine::from(compiler)
+}
+
+/// Generate a runtime `Engine` without compiler suitable for iOS.
+/// Useful for re-building an iOS Module from a preserialized WASM Module.
+pub fn make_ios_runtime_engine() -> Engine {
+    Engine::headless()
+}
+
+/// Take WASM binary and prepare a wasmer Module suitable for iOS
+pub fn build_ios_module(wasm: &[u8]) -> Result<Module, CompileError> {
+    info!(
+        "Found wasm and was instructed to serialize it for ios in wasmer format, doing so now..."
+    );
+    let compiler_engine = make_compiler_engine();
+    let store = Store::new(compiler_engine);
+    Module::from_binary(&store, wasm)
+}
+
+/// Deserialize a previously compiled module for iOS from a file.
+pub fn get_ios_module_from_file(path: &PathBuf) -> Result<Module, DeserializeError> {
+    let engine = make_ios_runtime_engine();
+    unsafe { Module::deserialize_from_file(&engine, path) }
+}
+
+/// Configuration of a Target for wasmer for iOS
+pub fn wasmer_ios_target() -> Target {
+    // use what I see in
+    // platform ios headless example
+    // https://github.com/wasmerio/wasmer/blob/447c2e3a152438db67be9ef649327fabcad6f5b8/examples/platform_ios_headless.rs#L38-L53
+    let triple = Triple::from_str("aarch64-apple-ios").unwrap();
+    let cpu_feature = CpuFeature::set();
+    Target::new(triple, cpu_feature)
+}
+
 /// Cache for serialized modules. These are fully compiled wasm modules that are
 /// then serialized by wasmer and can be cached. A serialized wasm module must still
 /// be deserialized before it can be used to build instances. The deserialization
@@ -128,7 +193,12 @@ pub struct SerializedModuleCache {
     pub plru: MicroCache,
     pub key_map: PlruKeyMap,
     pub cache: BTreeMap<CacheKey, Arc<SerializedModule>>,
-    pub cranelift: fn() -> Cranelift,
+    // a function to create a new compiler engine for every module
+    pub make_compiler_engine: fn() -> Engine,
+    // the runtime engine has to live as long as the module;
+    // keeping it in the cache and using it for all modules
+    // make sure of that
+    pub runtime_engine: Engine,
     pub maybe_fs_dir: Option<PathBuf>,
 }
 
@@ -157,15 +227,21 @@ impl PlruCache for SerializedModuleCache {
 }
 
 impl SerializedModuleCache {
-    /// Build a default `SerializedModuleCache` with a `Cranelift` that will be used
-    /// to compile modules for serialization as needed.
-    pub fn default_with_cranelift(cranelift: fn() -> Cranelift) -> Self {
+    /// Build a default `SerializedModuleCache` with a fn to create an `Engine`
+    /// that will be used to compile modules from wasms as needed.
+    pub fn default_with_engine(
+        make_compiler_engine: fn() -> Engine,
+        maybe_fs_dir: Option<PathBuf>,
+    ) -> Self {
         Self {
-            cranelift,
+            make_compiler_engine,
+            // the engine to execute function calls on instances does not
+            // require a compiler
+            runtime_engine: Engine::headless(),
             plru: MicroCache::default(),
             key_map: PlruKeyMap::default(),
             cache: BTreeMap::default(),
-            maybe_fs_dir: None,
+            maybe_fs_dir,
         }
     }
 
@@ -175,27 +251,13 @@ impl SerializedModuleCache {
             .map(|dir_path| dir_path.clone().join(hex::encode(key)))
     }
 
-    fn store(&self) -> Store {
-        let mut engine: Engine = (self.cranelift)().into();
-        // Workaround for invalid memory access on iOS.
-        // https://github.com/holochain/holochain/issues/3096
-        engine.set_tunables(BaseTunables {
-            static_memory_bound: 0x4000.into(),
-            static_memory_offset_guard_size: 0x1_0000,
-            dynamic_memory_offset_guard_size: 0x1_0000,
-        });
-        Store::new(engine)
-    }
-
-    /// Given a wasm, compiles with cranelift, serializes the result, adds it to
+    /// Given a wasm, compiles with compiler engine, serializes the result, adds it to
     /// the cache and returns that.
     fn get_with_build_cache(
         &mut self,
         key: CacheKey,
         wasm: &[u8],
-    ) -> Result<Arc<ModuleWithStore>, wasmer::RuntimeError> {
-        let store = self.store();
-
+    ) -> Result<Arc<Module>, wasmer::RuntimeError> {
         let maybe_module_path = self.module_path(key);
         let (module, serialized_module) = match maybe_module_path.as_ref().map(|module_path| {
             // We do this the long way to get `Bytes` instead of `Vec<u8>` so
@@ -218,13 +280,27 @@ impl SerializedModuleCache {
             })?;
             Ok::<bytes::Bytes, wasmer::RuntimeError>(bytes_mut.into_inner().freeze())
         }) {
-            Some(Ok(serialized_module)) => (
-                unsafe { Module::deserialize(&store, serialized_module.clone()) }
-                    .map_err(|e| wasm_error!(WasmErrorInner::Compile(e.to_string())))?,
-                serialized_module,
-            ),
+            Some(Ok(serialized_module)) => {
+                let deserialized_module =
+                    unsafe { Module::deserialize(&self.runtime_engine, serialized_module.clone()) }
+                        .map_err(|e| wasm_error!(WasmErrorInner::Compile(e.to_string())))?;
+                (deserialized_module, serialized_module)
+            }
+            // no serialized module found on the file system, so serialize the
+            // wasm binary and write it to the file system
             _fs_miss => {
-                let module = Module::from_binary(&store, wasm)
+                // Each module needs to be compiled with a new engine because
+                // of middleware like metering. Middleware is compiled into the
+                // module once and available in all instances created from it.
+                let mut compiler_engine = (self.make_compiler_engine)();
+                // Workaround for invalid memory access on iOS.
+                // https://github.com/holochain/holochain/issues/3096
+                compiler_engine.set_tunables(BaseTunables {
+                    static_memory_bound: 0x4000.into(),
+                    static_memory_offset_guard_size: 0x1_0000,
+                    dynamic_memory_offset_guard_size: 0x1_0000,
+                });
+                let module = Module::from_binary(&compiler_engine, wasm)
                     .map_err(|e| wasm_error!(WasmErrorInner::Compile(e.to_string())))?;
                 let serialized_module = module
                     .serialize()
@@ -252,53 +328,61 @@ impl SerializedModuleCache {
                     }
                 }
 
+                // deserialize the module to be returned for instantiation
+                //
+                // A new middleware per module is required, hence a new engine
+                // per module is needed too. Serialization allows for uncoupling
+                // the module from the engine that was used for compilation.
+                // After that another engine can be used to deserialize the
+                // module again. The engine has to live as long as the module to
+                // prevent memory access out of bounds errors.
+                //
+                // This procedure facilitates caching of modules that can be
+                // instatiated with fresh stores free from state. Instance
+                // creation is highly performant which makes caching of instances
+                // and stores unnecessary.
+                let module = unsafe {
+                    Module::deserialize(&self.runtime_engine, serialized_module.clone())
+                        .map_err(|e| wasm_error!(WasmErrorInner::Compile(e.to_string())))?
+                };
+
                 (module, serialized_module)
             }
         };
         self.put_item(key, Arc::new(serialized_module.clone()));
 
-        Ok(Arc::new(ModuleWithStore {
-            store: Arc::new(Mutex::new(store)),
-            module: Arc::new(module),
-        }))
+        Ok(Arc::new(module))
     }
 
     /// Given a wasm, attempts to get the serialized module for it from the cache.
-    /// If the cache misses a new serialized module, will be built from the wasm.
-    pub fn get(
-        &mut self,
-        key: CacheKey,
-        wasm: &[u8],
-    ) -> Result<Arc<ModuleWithStore>, wasmer::RuntimeError> {
+    /// If the cache misses, a new serialized module will be built from the wasm.
+    pub fn get(&mut self, key: CacheKey, wasm: &[u8]) -> Result<Arc<Module>, wasmer::RuntimeError> {
         match self.cache.get(&key) {
             Some(serialized_module) => {
-                let store = self.store();
-                let module = unsafe { Module::deserialize(&store, (**serialized_module).clone()) }
-                    .map_err(|e| wasm_error!(WasmErrorInner::Compile(e.to_string())))?;
+                let module = unsafe {
+                    Module::deserialize(&self.runtime_engine, (**serialized_module).clone())
+                }
+                .map_err(|e| wasm_error!(WasmErrorInner::Compile(e.to_string())))?;
                 self.touch(&key);
-                Ok(Arc::new(ModuleWithStore {
-                    store: Arc::new(Mutex::new(store)),
-                    module: Arc::new(module),
-                }))
+                Ok(Arc::new(module))
             }
             None => self.get_with_build_cache(key, wasm),
         }
     }
 }
 
-/// Caches wasm instances. Reusing wasm instances allows maximum speed in function
-/// calls but also introduces the possibility of memory corruption or other bad
-/// state that is inappropriate to persist/reuse/access across calls. It is the
-/// responsibility of the host to discard instances that are not eligible for reuse.
+/// Caches deserialized wasm modules. Deserialization of cached modules from
+/// the cache to create callable instances is slow. Therefore modules are
+/// cached in memory after deserialization.
 #[derive(Default, Debug)]
-pub struct InstanceCache {
+pub struct DeserializedModuleCache {
     plru: MicroCache,
     key_map: PlruKeyMap,
-    cache: BTreeMap<CacheKey, Arc<InstanceWithStore>>,
+    cache: BTreeMap<CacheKey, Arc<Module>>,
 }
 
-impl PlruCache for InstanceCache {
-    type Item = InstanceWithStore;
+impl PlruCache for DeserializedModuleCache {
+    type Item = Module;
 
     fn plru_mut(&mut self) -> &mut MicroCache {
         &mut self.plru
@@ -320,3 +404,97 @@ impl PlruCache for InstanceCache {
         &mut self.cache
     }
 }
+
+#[derive(Debug)]
+pub struct ModuleCache {
+    serialized_module_cache: Arc<RwLock<SerializedModuleCache>>,
+    deserialized_module_cache: Arc<RwLock<DeserializedModuleCache>>,
+}
+
+impl ModuleCache {
+    pub fn new(maybe_fs_dir: Option<PathBuf>) -> Self {
+        let serialized_module_cache = Arc::new(RwLock::new(
+            SerializedModuleCache::default_with_engine(make_compiler_engine, maybe_fs_dir),
+        ));
+        let deserialized_module_cache = Arc::new(RwLock::new(DeserializedModuleCache::default()));
+        ModuleCache {
+            serialized_module_cache,
+            deserialized_module_cache,
+        }
+    }
+
+    pub fn get(&self, key: CacheKey, wasm: &[u8]) -> Result<Arc<Module>, wasmer::RuntimeError> {
+        // check deserialized module cache first for module
+        {
+            let mut deserialized_cache = self.deserialized_module_cache.write();
+            if let Some(module) = deserialized_cache.get_item(&key) {
+                return Ok(module);
+            }
+        }
+        // get module from serialized cache otherwise
+        // if cache does not contain module, it will be built from wasm bytes
+        // and then cached in serialized cache
+        let module;
+        {
+            let mut serialized_cache = self.serialized_module_cache.write();
+            module = serialized_cache.get(key, wasm)?;
+        }
+        // cache in deserialized module cache too
+        {
+            let mut deserialized_cache = self.deserialized_module_cache.write();
+            deserialized_cache.put_item(key, module.clone());
+        }
+        Ok(module)
+    }
+}
+
+#[cfg(test)]
+pub mod tests {
+    use crate::module::{CacheKey, ModuleCache, PlruCache};
+
+    #[test]
+    fn cache_test() {
+        // simple example wasm taken from wasmer docs
+        // https://docs.rs/wasmer/latest/wasmer/struct.Module.html#example
+        let wasm: Vec<u8> = vec![
+            0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00, 0x01, 0x06, 0x01, 0x60, 0x01, 0x7f,
+            0x01, 0x7f, 0x03, 0x02, 0x01, 0x00, 0x07, 0x0b, 0x01, 0x07, 0x61, 0x64, 0x64, 0x5f,
+            0x6f, 0x6e, 0x65, 0x00, 0x00, 0x0a, 0x09, 0x01, 0x07, 0x00, 0x20, 0x00, 0x41, 0x01,
+            0x6a, 0x0b, 0x00, 0x1a, 0x04, 0x6e, 0x61, 0x6d, 0x65, 0x01, 0x0a, 0x01, 0x00, 0x07,
+            0x61, 0x64, 0x64, 0x5f, 0x6f, 0x6e, 0x65, 0x02, 0x07, 0x01, 0x00, 0x01, 0x00, 0x02,
+            0x70, 0x30,
+        ];
+        let module_cache = ModuleCache::new(None);
+        assert_eq!(
+            module_cache.serialized_module_cache.read().cache.is_empty(),
+            true
+        );
+        assert_eq!(
+            module_cache
+                .deserialized_module_cache
+                .read()
+                .cache
+                .is_empty(),
+            true
+        );
+
+        let key: CacheKey = [0u8; 32].into();
+        let module = module_cache.get(key.clone(), &wasm).unwrap();
+
+        // make sure module has been stored in serialized cache under key
+        {
+            let serialized_cached_module =
+                module_cache.serialized_module_cache.write().get_item(&key);
+            assert_eq!(matches!(serialized_cached_module, Some(_)), true);
+        }
+        // make sure module has been stored in deserialized cache under key
+        {
+            let deserialized_cached_module = module_cache
+                .deserialized_module_cache
+                .write()
+                .get_item(&key)
+                .unwrap();
+            assert_eq!(*deserialized_cached_module, *module);
+        }
+    }
+}