feat(event streaming): configurable worker path, use SharedWorker (#2080

)

This commit allows any worker path to be used instead of hardcoded worker.js file. The worker path can be specified using worker_path in event_stream_configuration, if not specified worker.js will be used as default. Also, shared worker is used to allow using event streaming worker from multiple contexts.

mm2src/mm2_event_stream/src/lib.rs

@@ -1,5 +1,9 @@
 use serde::Deserialize;
 use std::collections::HashMap;
+#[cfg(target_arch = "wasm32")] use std::path::PathBuf;
+
+#[cfg(target_arch = "wasm32")]
+const DEFAULT_WORKER_PATH: &str = "event_streaming_worker.js";
 
 /// Multi-purpose/generic event type that can easily be used over the event streaming
 pub struct Event {
@@ -34,8 +38,16 @@ pub struct EventStreamConfiguration {
     pub access_control_allow_origin: String,
     #[serde(default)]
     active_events: HashMap<String, EventConfig>,
+    /// The path to the worker script for event streaming.
+    #[cfg(target_arch = "wasm32")]
+    #[serde(default = "default_worker_path")]
+    pub worker_path: PathBuf,
 }
 
+#[cfg(target_arch = "wasm32")]
+#[inline]
+fn default_worker_path() -> PathBuf { PathBuf::from(DEFAULT_WORKER_PATH) }
+
 /// Represents the configuration for a specific event within the event stream.
 #[derive(Clone, Default, Deserialize)]
 pub struct EventConfig {
@@ -51,6 +63,8 @@ impl Default for EventStreamConfiguration {
         Self {
             access_control_allow_origin: String::from("*"),
             active_events: Default::default(),
+            #[cfg(target_arch = "wasm32")]
+            worker_path: default_worker_path(),
         }
     }
 }

mm2src/mm2_net/Cargo.toml

@@ -49,7 +49,7 @@ wasm-bindgen-futures = "0.4.21"
 web-sys = { version = "0.3.55", features = ["console", "CloseEvent", "DomException", "ErrorEvent", "IdbDatabase",
     "IdbCursor", "IdbCursorWithValue", "IdbFactory", "IdbIndex", "IdbIndexParameters", "IdbObjectStore",
     "IdbObjectStoreParameters", "IdbOpenDbRequest", "IdbKeyRange", "IdbTransaction", "IdbTransactionMode",
-    "IdbVersionChangeEvent", "MessageEvent", "ReadableStreamDefaultReader", "ReadableStream", "WebSocket", "Worker"] }
+    "IdbVersionChangeEvent", "MessageEvent", "MessagePort", "ReadableStreamDefaultReader", "ReadableStream", "SharedWorker", "WebSocket"] }
 
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]

mm2src/mm2_net/src/wasm_event_stream.rs

@@ -1,5 +1,14 @@
 use mm2_core::mm_ctx::MmArc;
 use serde_json::json;
+use web_sys::SharedWorker;
+
+struct SendableSharedWorker(SharedWorker);
+
+unsafe impl Send for SendableSharedWorker {}
+
+struct SendableMessagePort(web_sys::MessagePort);
+
+unsafe impl Send for SendableMessagePort {}
 
 /// Handles broadcasted messages from `mm2_event_stream` continuously for WASM.
 pub async fn handle_worker_stream(ctx: MmArc) {
@@ -11,16 +20,34 @@ pub async fn handle_worker_stream(ctx: MmArc) {
     let mut channel_controller = ctx.stream_channel_controller.clone();
     let mut rx = channel_controller.create_channel(config.total_active_events());
 
+    let worker_path = config
+        .worker_path
+        .to_str()
+        .expect("worker_path contains invalid UTF-8 characters");
+    let worker = SendableSharedWorker(
+        SharedWorker::new(worker_path).unwrap_or_else(|_| {
+            panic!(
+                "Failed to create a new SharedWorker with path '{}'.\n\
+                This could be due to the file missing or the browser being incompatible.\n\
+                For more details, please refer to https://developer.mozilla.org/en-US/docs/Web/API/SharedWorker#browser_compatibility",
+                worker_path
+            )
+        }),
+    );
+
+    let port = SendableMessagePort(worker.0.port());
+    port.0.start();
+
     while let Some(event) = rx.recv().await {
         let data = json!({
             "_type": event.event_type(),
             "message": event.message(),
         });
-
-        let worker = web_sys::Worker::new("worker.js").expect("Missing worker.js");
         let message_js = wasm_bindgen::JsValue::from_str(&data.to_string());
 
-        worker.post_message(&message_js)
-            .expect("Incompatible browser!\nSee https://developer.mozilla.org/en-US/docs/Web/API/Worker/postMessage#browser_compatibility for details.");
+        port.0.post_message(&message_js)
+            .expect("Failed to post a message to the SharedWorker.\n\
+            This could be due to the browser being incompatible.\n\
+            For more details, please refer to https://developer.mozilla.org/en-US/docs/Web/API/MessagePort/postMessage#browser_compatibility");
     }
 }