Fix instance memory leak

Cargo.toml

@@ -7,7 +7,7 @@ members = [
     "worker-sys",
     "worker-kv",
     "examples/*",
-    "test/container-echo",
+    "test/container-echo"
 ]
 exclude = ["examples/coredump", "examples/axum", "templates/*", "wasm-bindgen"]
 resolver = "2"
@@ -20,17 +20,22 @@ chrono = { version = "0.4.41", default-features = false, features = [
 futures-channel = "0.3.31"
 futures-util = { version = "0.3.31", default-features = false }
 http = "1.3"
-js-sys = { version = "0.3.78", path = "./wasm-bindgen/crates/js-sys" }
+js-sys = { version = "0.3.80", path = "./wasm-bindgen/crates/js-sys" }
 serde = { version = "1.0.164", features = ["derive"] }
 serde_json = "1.0.140"
 serde-wasm-bindgen = "0.6.5"
 wasm-bindgen = { version = "0.2.103", path = "./wasm-bindgen" }
 wasm-bindgen-cli-support = { version = "0.2.103", path = "./wasm-bindgen/crates/cli-support" }
-wasm-bindgen-futures = { version = "0.4.51", path = "./wasm-bindgen/crates/futures" }
+wasm-bindgen-futures = { version = "0.4.53", path = "./wasm-bindgen/crates/futures" }
 wasm-bindgen-macro-support = { version = "0.2.103", path = "./wasm-bindgen/crates/macro-support" }
 wasm-bindgen-shared = { version = "0.2.103", path = "./wasm-bindgen/crates/shared" }
 wasm-bindgen-test = { version = "0.3.51", path = "./wasm-bindgen/crates/test" }
-web-sys = { version = "0.3.79", path = "./wasm-bindgen/crates/web-sys" }
+web-sys = { version = "0.3.80", features = [
+    "File",
+    "ReadableStreamDefaultReader",
+    "WorkerGlobalScope",
+    "WritableStreamDefaultWriter",
+] }
 worker = { path = "worker", version = "0.6.5", features = ["queue", "d1", "axum", "timezone"] }
 worker-codegen = { path = "worker-codegen", version = "0.2.0" }
 worker-kv = { path = "worker-kv", version = "0.9.0" }
@@ -61,11 +66,11 @@ codegen-units = 1
 opt-level = "z"
 
 [patch.crates-io]
-js-sys = { version = "0.3.79", path = './wasm-bindgen/crates/js-sys' }
+js-sys = { version = "0.3.80", path = './wasm-bindgen/crates/js-sys' }
 wasm-bindgen = { version = "0.2.103", path = './wasm-bindgen' }
 wasm-bindgen-cli-support = { version = "0.2.103", path = "./wasm-bindgen/crates/cli-support" }
-wasm-bindgen-futures = { version = "0.4.51", path = './wasm-bindgen/crates/futures' }
+wasm-bindgen-futures = { version = "0.4.53", path = './wasm-bindgen/crates/futures' }
 wasm-bindgen-macro-support = { version = "0.2.103", path = "./wasm-bindgen/crates/macro-support" }
 wasm-bindgen-shared = { version = "0.2.103", path = "./wasm-bindgen/crates/shared" }
 wasm-bindgen-test = { version = "0.3.51", path = "./wasm-bindgen/crates/test" }
-web-sys = { version = "0.3.79", path = './wasm-bindgen/crates/web-sys' }
+web-sys = { version = "0.3.80", path = './wasm-bindgen/crates/web-sys' }

package.json

@@ -15,16 +15,17 @@
   "homepage": "https://github.com/cloudflare/workers-rs#readme",
   "devDependencies": {
     "@types/node": "^24.0.1",
-    "miniflare": "^4.20250823.0",
+    "miniflare": "^4.20250923.0",
     "typescript": "^5.8.3",
-    "undici": "^7.12.0",
+    "undici": "7.14.0",
     "uuid": "^11.1.0",
     "vitest": "^3.2.4"
   },
   "scripts": {
     "build": "cd wasm-bindgen && cargo build -p wasm-bindgen-cli --bin wasm-bindgen && cd .. && cargo build -p worker-build",
     "test": "cd test && NO_MINIFY=1 WASM_BINDGEN_PATH=../wasm-bindgen/target/debug/wasm-bindgen ../target/debug/worker-build --dev && NODE_OPTIONS='--experimental-vm-modules' npx vitest run",
     "test-http": "cd test && NO_MINIFY=1 WASM_BINDGEN_PATH=../wasm-bindgen/target/debug/wasm-bindgen ../target/debug/worker-build --release --features http && NODE_OPTIONS='--experimental-vm-modules' npx vitest run",
+    "test-mem": "cd test && npx wrangler dev --enable-containers=false",
     "lint": "cargo clippy --features d1,queue --all-targets --workspace -- -D warnings",
     "lint:fix": "cargo fmt && cargo clippy --features d1,queue --all-targets --workspace --fix -- -D warnings"
   }

test/src/alarm.rs

@@ -6,36 +6,34 @@ use super::SomeSharedData;
 #[durable_object]
 pub struct AlarmObject {
     state: State,
+    // used for memory leak detection
+    _buffer: Vec<u8>,
 }
 
 impl DurableObject for AlarmObject {
     fn new(state: State, _: Env) -> Self {
-        Self { state }
+        Self {
+            state,
+            _buffer: Vec::with_capacity(111_000_000),
+        }
     }
 
     async fn fetch(&self, _: Request) -> Result<Response> {
+        self.state
+            .storage()
+            .set_alarm(Duration::from_millis(100))
+            .await?;
         let alarmed: bool = match self.state.storage().get("alarmed").await {
             Ok(alarmed) => alarmed,
-            Err(e) if e.to_string() == "No such value in storage." => {
-                // Trigger our alarm method in 100ms.
-                self.state
-                    .storage()
-                    .set_alarm(Duration::from_millis(100))
-                    .await?;
-
-                false
-            }
+            Err(e) if e.to_string() == "No such value in storage." => false,
             Err(e) => return Err(e),
         };
-
         Response::ok(alarmed.to_string())
     }
 
     async fn alarm(&self) -> Result<Response> {
         self.state.storage().put("alarmed", true).await?;
-
         console_log!("Alarm has been triggered!");
-
         Response::ok("ALARMED")
     }
 }

test/wrangler.toml

@@ -1,7 +1,6 @@
 name = "testing-rust-worker"
 workers_dev = true
-compatibility_date = "2022-09-12"                     # required
-compatibility_flags = ["streams_enable_constructors"]
+compatibility_date = "2025-09-23"                     # required
 main = "build/worker/shim.mjs"
 
 kv_namespaces = [
@@ -70,7 +69,7 @@ bucket_name = 'delete-bucket'
 preview_bucket_name = 'delete-bucket'
 
 [build]
-command = "../target/debug/worker-build --release"
+command = "WASM_BINDGEN_PATH=../wasm-bindgen/target/debug/wasm-bindgen ../target/debug/worker-build --release"
 
 [[migrations]]
 tag = "v1"

worker-build/src/js/shim.js

@@ -2,9 +2,9 @@ import { WorkerEntrypoint } from "cloudflare:workers";
 import * as exports from "./index.js";
 export * from "./index.js";
 
-let panicError = null;
 Error.stackTraceLimit = 100;
 
+let panicError = null;
 function registerPanicHook() {
   exports.setPanicHook(function (message) {
     panicError = new Error("Critical Rust panic: " + message);
@@ -14,55 +14,37 @@ function registerPanicHook() {
 
 registerPanicHook();
 
+let instanceId = 0;
 function checkReinitialize() {
   if (panicError) {
     console.log("Reinitializing Wasm application");
     exports.__wbg_reset_state();
     panicError = null;
     registerPanicHook();
-    for (const instance of instances) {
-      const newInstance = Reflect.construct(instance.target, instance.args, instance.newTarget);
-      instance.instance = newInstance;
-    }
+    instanceId++;
   }
 }
 
 export default class Entrypoint extends WorkerEntrypoint {
-  async fetch(request) {
-    checkReinitialize();
-    let response = exports.fetch(request, this.env, this.ctx);
-    $WAIT_UNTIL_RESPONSE;
-    return await response;
-  }
-
-  async queue(batch) {
-    checkReinitialize();
-    return await exports.queue(batch, this.env, this.ctx);
-  }
-
-  async scheduled(event) {
-    checkReinitialize();
-    return await exports.scheduled(event, this.env, this.ctx);
-  }
+$HANDLERS
 }
 
-const instances = [];
 const classProxyHooks = {
-  construct(target, args, newTarget) {
+  construct(ctor, args, newTarget) {
     const instance = {
-      instance: Reflect.construct(target, args, newTarget),
-      target,
+      instance: Reflect.construct(ctor, args, newTarget),
+      instanceId,
+      ctor,
       args,
       newTarget
     };
-    instances.push(instance);
     return new Proxy(instance, {
       get(target, prop, receiver) {
+        if (target.instanceId !== instanceId) {
+          target.instance = Reflect.construct(target.ctor, target.args, target.newTarget);
+          target.instanceId = instanceId;
+        }
         return Reflect.get(target.instance, prop, receiver);
-      },
-
-      set(target, prop, value, receiver) {
-        return Reflect.set(target.instance, prop, value, receiver);
       }
     });
   }

worker-build/src/main.rs

@@ -92,9 +92,8 @@ pub fn main() -> Result<()> {
     }
 
     if supports_module_and_reset_state {
-        update_package_json()?;
-
-        let esbuild_path = install::ensure_esbuild()?;
+        let (has_fetch_handler, has_queue_handler, has_scheduled_handler) =
+            detect_exported_handlers()?;
 
         let shim_template = match env::var("CUSTOM_SHIM") {
             Ok(path) => {
@@ -106,20 +105,49 @@ pub fn main() -> Result<()> {
             Err(_) => SHIM_FILE.to_owned(),
         };
 
-        let wait_until_response = if env::var("RUN_TO_COMPLETION").is_ok() {
-            "this.ctx.waitUntil(response);"
-        } else {
-            ""
-        };
+        let mut handlers = String::new();
+        if has_fetch_handler {
+            let wait_until_response = if env::var("RUN_TO_COMPLETION").is_ok() {
+                "this.ctx.waitUntil(response);"
+            } else {
+                ""
+            };
+            handlers += &format!(
+                "  async fetch(request) {{
+    checkReinitialize();
+    let response = exports.fetch(request, this.env, this.ctx);
+    {wait_until_response}
+    return await response;
+  }}
+"
+            )
+        }
+        if has_queue_handler {
+            handlers += "  async queue(batch) {
+    checkReinitialize();
+    return await exports.queue(batch, this.env, this.ctx);
+  }
+"
+        }
+        if has_scheduled_handler {
+            handlers += "  async scheduled(event) {
+    checkReinitialize();
+    return await exports.scheduled(event, this.env, this.ctx);
+  }
+"
+        }
 
-        let shim = shim_template.replace("$WAIT_UNTIL_RESPONSE", wait_until_response);
+        let shim = shim_template.replace("$HANDLERS", &handlers);
 
         fs::write(output_path("shim.js"), shim)?;
 
         fix_heap_assignment()?;
 
         add_exported_class_wrappers(detect_exported_class_names()?)?;
 
+        update_package_json()?;
+
+        let esbuild_path = install::ensure_esbuild()?;
         bundle(&esbuild_path)?;
 
         fix_wasm_import()?;
@@ -135,6 +163,32 @@ pub fn main() -> Result<()> {
     Ok(())
 }
 
+fn detect_exported_handlers() -> Result<(bool, bool, bool)> {
+    let index_path = output_path("index.js");
+    let content = fs::read_to_string(&index_path)?;
+
+    let mut has_fetch_handler = false;
+    let mut has_queue_handler = false;
+    let mut has_scheduled_handler = false;
+    for line in content.lines() {
+        if !line.contains("export function") {
+            continue;
+        }
+        if let Some(rest) = line.strip_prefix("export function") {
+            if let Some(bracket_pos) = rest.find("(") {
+                let func_name = rest[..bracket_pos].trim();
+                match func_name {
+                    "fetch" => has_fetch_handler = true,
+                    "queue" => has_queue_handler = true,
+                    "scheduled" => has_scheduled_handler = true,
+                    _ => {}
+                }
+            }
+        }
+    }
+    Ok((has_fetch_handler, has_queue_handler, has_scheduled_handler))
+}
+
 fn detect_exported_class_names() -> Result<Vec<String>> {
     let index_path = output_path("index.js");
     let content = fs::read_to_string(&index_path)?;

worker/Cargo.toml

@@ -39,12 +39,7 @@ worker-kv.workspace = true
 worker-macros.workspace = true
 worker-sys.workspace = true
 chrono-tz = { version = "0.10.3", optional = true, default-features = false }
-web-sys = { version = "0.3.70", features = [
-    "File",
-    "WorkerGlobalScope",
-    "ReadableStreamDefaultReader",
-    "WritableStreamDefaultWriter",
-] }
+web-sys.workspace = true
 tokio-postgres = { version = "0.7", optional = true, default-features = false, features = [
     "js",
 ] }