Documentation of the wasmer plugin prototype (wip)

developer/src/SUMMARY.md

@@ -5,7 +5,13 @@
 - [Architecture](architecture/README.md)
 - [Plugin System](plugin/README.md)
     - [Wasmer](plugin/wasmer/README.md)
-        - [Plugin Proposal](plugin/wasmer/proposal.md) 
+        - [Proposal](plugin/wasmer/proposal.md) 
+        - [Plugin Factory](plugin/wasmer/plugin-factory.md)
+        - [Plugin Proxy](plugin/wasmer/plugin-proxy.md)
+        - [Parser Plugin](plugin/wasmer/parser-plugin.md)
+        - [Source Plugin](plugin/wasmer/source-plugin.md)
+        - [Results](plugin/wasmer/results.md)
+        - [Conclusion](plugin/wasmer/conclusion.md)
     - [Wasmtime](plugin/wasmtime/README.md)
         - [Component Model](plugin/wasmtime/component-model.md)
         - [Advantages](plugin/wasmtime/advantages.md)

developer/src/plugin/wasmer/conclusion.md

@@ -0,0 +1,19 @@
+# Conclusion
+
+With the given approach plugins can be integrated easily into the host application, eg. in case of a `MessageProducer`:
+
+```rust,no_run
+        let source_plugin_factory = SourcePluginFactory::new();
+        let source_plugin = source_plugin_factory.create(0).unwrap();
+        let source = ByteSourceProxy::new(source_plugin, ...);
+
+        let dlt_plugin_factory = DltPluginFactory::new();
+        let dlt_plugin = dlt_plugin_factory.create(1).unwrap();
+        let dlt_parser = DltParserProxy::new(dlt_plugin, ...);
+
+        let mut dlt_msg_producer = MessageProducer::new(dlt_parser, source, ...);
+```
+
+Though, some difficulties with the current one-step processing logic of Chipmunk in contrast to performance saving bulk operations between the host and plugins have to be considered.
+
+Given the acceptable performance impact of this low-level WebAssembly approach using memory-copy, it could serve as a first integration step towards a plugin support for Chipmunk, however.

developer/src/plugin/wasmer/parser-plugin.md

@@ -0,0 +1,157 @@
+# Parser Plugin for Dlt
+
+The parser plugin for DLT is realized by a `wasm` module in `application/apps/indexer/plugin/dlt` together with a corresponding host proxy for the `Parser` trait in `application/apps/indexer/session/src/plugin`. 
+
+In order to minimize actual calls to the plugin, each data chunk provided to the proxy is being processed in a bulk operation within the plugin.
+
+## DltParser WASM module
+
+The plugin will parse a given chunk of data and return all results to the host.
+
+```rust,no_run
+// Singleton instance of the DltParser within the plugin.
+lazy_static! {
+    static ref PARSER: Mutex<DltParser<'static>> = DltParser::default().into();
+}
+
+#[repr(C)]
+pub struct Response(*mut u8, u32);
+
+#[allow(clippy::missing_safety_doc)]
+#[no_mangle]
+pub unsafe extern "C" fn message(ptr: *const u8, len: u32) -> Response {
+    // Get the instance of our parser.
+    let mut parser = PARSER.lock().unwrap_or_else(|error| panic("lock", &error.to_string()));
+
+    // Deserialize the request from the module's memory.
+    let input = unsafe { std::slice::from_raw_parts(ptr, len.try_into().unwrap()) };
+    let request = rkyv::from_bytes(input).unwrap_or_else(|error| panic("from_bytes", &error.to_string()));
+
+    // Process the request.
+    let response = match request {
+        PluginRpc::Request(DltParserRpc::Setup(ParserSettings {
+            with_storage_header,
+        })) => {
+            print("init parser");
+            parser.with_storage_header = with_storage_header;
+            PluginRpc::Response(DltParserRpc::SetupDone)
+        }
+        PluginRpc::Request(DltParserRpc::Parse(ParseInput { bytes })) => {
+            let response: PluginRpc<DltParserRpc>;
+            let mut results: Vec<ParserResult> = Vec::new();
+            let mut input: &[u8] = &bytes;
+            loop {
+                match parser.parse(input, None) {
+                    Ok((rest, Some(result))) => {
+                        let bytes_remaining = rest.len();
+                        let message = match result {
+                            ParseYield::Message(message) => {
+                                print(&format!("parse message ({} bytes remaining)", bytes_remaining));
+                                Some(format!("{}", message)) // TODO
+                            }
+                            ...
+                        };
+                        results.push(ParserResult::ParseOk(ParseOutput {
+                            bytes_remaining,
+                            message,
+                        }));
+                        if rest.is_empty() {
+                            response = PluginRpc::Response(DltParserRpc::ParseResult(results));
+                            break;
+                        } else {
+                            input = rest;
+                        }
+                    }
+                    ...
+                };
+            }
+            response
+        }
+        ...
+    };
+
+    // Serialize the response to the module's memory.
+    let mut output = rkyv::to_bytes::<_, 256>(&response).unwrap_or_else(|error| panic("to_bytes", &error.to_string()));
+    let ptr = output.as_mut_ptr();
+    let len = output.len();
+    mem::forget(output);
+
+    Response(ptr, len as u32)
+}
+```
+
+## DltParser Host proxy
+
+The proxy will store the results retrieved from the plugin and returns them to the host as long as unconsumed results are available.
+
+```rust,no_run
+impl DltParserProxy {
+    pub fn new(mut proxy: PluginProxy, with_storage_header: bool) -> Self {
+        // Init plugin with given settings.
+        let request: PluginRpc<DltParserRpc> =
+            PluginRpc::Request(DltParserRpc::Setup(ParserSettings {
+                with_storage_header,
+            }));
+        let request_bytes = rkyv::to_bytes::<_, 256>(&request).unwrap();
+
+        match proxy.call(&request_bytes) {
+            Ok(response_bytes) => {
+                let response: PluginRpc<DltParserRpc> = rkyv::from_bytes(&response_bytes).unwrap();
+                if let PluginRpc::Response(DltParserRpc::SetupDone) = response {
+                    // nothing
+                } 
+                ...
+            }
+            ...
+        }
+
+        Self {
+            proxy,
+            results: VecDeque::new(), // Current bulk results from plugin.
+        }
+    }
+
+    // Returns the next item from stored results.
+    fn next_result<'b>(
+        &mut self,
+        input: &'b [u8],
+    ) -> Option<Result<(&'b [u8], Option<ParseYield<DltProxyMessage>>), ParserError>> {
+        ...
+    }
+}
+
+impl Parser<DltProxyMessage> for DltParserProxy {
+    fn parse<'b>(
+        &mut self,
+        input: &'b [u8],
+        _timestamp: Option<u64>,
+    ) -> Result<(&'b [u8], Option<ParseYield<DltProxyMessage>>), ParserError> {
+        // As long as we have stored results we return next item.
+        if let Some(result) = self.next_result(input) {
+            return result;
+        }
+
+        // Create request with next chunk of data to be parsed.
+        let request: PluginRpc<DltParserRpc> =
+            PluginRpc::Request(DltParserRpc::Parse(ParseInput {
+                bytes: input.to_vec(),
+            }));
+        let request_bytes = rkyv::to_bytes::<_, 256>(&request).unwrap();
+
+        match self.proxy.call(&request_bytes) {
+            Ok(response_bytes) => {
+                let response: PluginRpc<DltParserRpc> = rkyv::from_bytes(&response_bytes).unwrap();
+                if let PluginRpc::Response(DltParserRpc::ParseResult(results)) = response {
+                    
+                    // Store results and return first item, if any.
+                    self.results = VecDeque::from(results);
+                    if let Some(result) = self.next_result(input) {
+                        result
+                    } 
+                    ...
+            }
+            ...
+        }
+    }
+}
+```

developer/src/plugin/wasmer/plugin-factory.md

@@ -0,0 +1,151 @@
+# Plugin Factory
+
+In `application/apps/indexer/plugin/host` some generic host components are defined, such as the trait for a plugin factory and its actual implementations for `wasm` and `wasi` plugins:
+
+```rust,no_run
+pub trait PluginFactory {
+    fn create(&self, id: PluginId) -> Result<PluginProxy, PluginError>;
+}
+```
+
+## Wasm Plugin Factory
+
+The implementation for a plain `wasm` plugin factory would get a precompiled WebAssembly binary and instantiate a proxy based on the `wasmer` runtime:
+
+```rust,no_run
+use wasmer::{
+    imports, AsStoreRef, Function, FunctionEnv, FunctionEnvMut, Instance, Memory, Module, Store,
+    TypedFunction, WasmPtr, WasmSlice,
+};
+...
+
+impl WasmPluginFactory {
+    pub fn new(binary: Vec<u8>) -> Self {
+        WasmPluginFactory { binary }
+    }
+}
+
+impl PluginFactory for WasmPluginFactory {
+    fn create(&self, id: PluginId) -> Result<PluginProxy, PluginError> {
+        let mut store = Store::default();
+
+        // Load the module from the precompiled binary.
+        let module = Module::from_binary(&store, &self.binary).expect("from_binary");
+
+        // Create a plugin environment to be used at runtime.
+        let plugin_env = FunctionEnv::new(&mut store, PluginEnv { id, memory: None });
+
+        // Add a debug-print function from the host to be imported in the plugin.
+        let host_print = Function::new_typed_with_env(
+            &mut store,
+            &plugin_env,
+            |env: FunctionEnvMut<PluginEnv>, ptr: WasmPtr<u8>, len: u32| {
+                let store = env.as_store_ref();
+                let memory = env.data().memory.as_ref().unwrap();
+                let memory_view = memory.view(store.borrow());
+                let string = ptr.read_utf8_string(&memory_view, len).unwrap();
+                debug!("proxy<{}> : {}", env.data().id, string);
+            },
+        );
+
+        let imports = imports! {
+            "host" => {
+                "host_print" => host_print,
+            },
+        };
+
+        // Create an instance of the plugin runtime.
+        let instance = Instance::new(&mut store, &module, &imports).expect("instance");
+
+        // Add the instance's memory to the plugin-env so it could be accessed from import functions.
+        let env = plugin_env.as_mut(&mut store);
+        env.memory = Some(
+            instance.exports.get_memory("memory").expect("memory").clone(),
+        );
+
+        Ok(PluginProxy::new(id, store, instance))
+    }
+}
+```
+
+## Wasi Plugin Factory
+
+The implementation for a `wasi` plugin factory would respectively get a precompiled WebAssembly binary and instantiate a proxy based on the `wasmer` runtime and a `wasmer_wasix` environment to support eg. system I/O operations:
+
+```rust,no_run
+use wasmer::{
+    AsStoreRef, Function, FunctionEnv, FunctionEnvMut, Instance, Memory, Module, Store,
+    TypedFunction, WasmPtr, WasmSlice,
+};
+use wasmer_wasix::{default_fs_backing, WasiEnv};
+
+impl WasiPluginFactory {
+    pub fn new(binary: Vec<u8>) -> Self {
+        WasiPluginFactory { binary }
+    }
+}
+
+impl PluginFactory for WasiPluginFactory {
+    fn create(&self, id: PluginId) -> Result<PluginProxy, PluginError> {
+        let mut store = Store::default();
+
+        // Load the module from the precompiled binary.
+        let module = Module::from_binary(&store, &self.binary).expect("from_binary");
+
+        // Create a wasi environment to be used at runtime and map pre-opened host file handles.
+        let mut wasi_env = WasiEnv::builder(format!("wasi-proxy<{}>", id))
+            .fs(default_fs_backing())
+            .preopen_dir(Path::new("/")) // NOTE: Map currently only the working-directory of the application.
+            .expect("preopen_dir")
+            .map_dir("/", ".")
+            .expect("map_dir")
+            .finalize(&mut store)
+            .expect("finalize_env");
+
+        let mut imports = wasi_env
+            .import_object(&mut store, &module)
+            .expect("imports");
+
+        // Create a plugin environment to be used at runtime.
+        let plugin_env = FunctionEnv::new(&mut store, PluginEnv { id, memory: None });
+
+        // Add a debug-print function from the host to be imported in the plugin.
+        let host_print = Function::new_typed_with_env(
+            &mut store,
+            &plugin_env,
+            |env: FunctionEnvMut<PluginEnv>, ptr: WasmPtr<u8>, len: u32| {
+                let store = env.as_store_ref();
+                let memory = env.data().memory.as_ref().unwrap();
+                let memory_view = memory.view(store.borrow());
+                let string = ptr.read_utf8_string(&memory_view, len).unwrap();
+                debug!("proxy<{}> : {}", env.data().id, string);
+            },
+        );
+
+        imports.define("host", "host_print", host_print);
+
+        // Create an instance of the plugin runtime.
+        let instance = Instance::new(&mut store, &module, &imports).expect("instance");
+
+        // Initialize the wasi environment
+        wasi_env
+            .initialize(&mut store, instance.clone())
+            .expect("initialize_env");
+
+        // Add the instance's memory to the plugin-env so it could be accessed from import functions.
+        let env = plugin_env.as_mut(&mut store);
+        env.memory = Some(
+            instance.exports.get_memory("memory").expect("memory").clone(),
+        );
+
+        // Start the wasi plugin as a reactor.
+        let start = instance
+            .exports
+            .get_function("_initialize")
+            .expect("exports");
+        start.call(&mut store, &[]).expect("start");
+
+        Ok(PluginProxy::new(id, store, instance))
+    }
+}
+```