Exposing env specific scheduler and passing it through Realm config

Author: Kræn Hansen

packages/realm/bindgen/src/templates/node-wrapper.ts

@@ -36,6 +36,8 @@ export function generate(context: TemplateContext): void {
 
     // We know that node always has real WeakRefs so just use them.
     export const WeakRef = global.WeakRef;
+    // Export a special function to get the env specific scheduler
+    export const getPlatformScheduler = nativeModule.getPlatformScheduler;
   `);
 
   generateNativeBigIntSupport(out);

packages/realm/bindgen/src/templates/node.ts

@@ -83,7 +83,7 @@ class NodeAddon extends CppClass {
     this.withCrtpBase("Napi::Addon");
 
     this.members.push(new CppVar("std::deque<std::string>", "m_string_bufs"));
-    this.members.push(new CppVar("std::shared_ptr<NapiScheduler>", "m_scheduler"));
+    this.members.push(new CppVar("std::shared_ptr<util::Scheduler>", "m_scheduler"));
     this.addMethod(
       new CppMethod("wrapString", "const std::string&", [new CppVar("std::string", "str")], {
         attributes: "inline",
@@ -105,6 +105,8 @@ class NodeAddon extends CppClass {
     this.classes.forEach((t) =>
       this.members.push(new CppVar("Napi::FunctionReference", NodeAddon.memberNameForExtractor(t))),
     );
+
+    // Injectables
     this.addMethod(
       new CppMethod("injectInjectables", "void", [node_callback_info], {
         body: `
@@ -123,6 +125,16 @@ class NodeAddon extends CppClass {
       }),
     );
 
+    // Env specific scheduler
+    this.addMethod(
+      new CppMethod("getPlatformScheduler", "Napi::Value", [node_callback_info], {
+        body: `
+          const auto env = info.Env();
+          return NODE_FROM_SHARED_Scheduler(env, env.GetInstanceData<RealmAddon>()->m_scheduler);
+        `,
+      }),
+    );
+
     this.addMethod(
       new CppCtor(this.name, [new CppVar("Napi::Env", env), new CppVar("Napi::Object", "exports")], {
         mem_inits: [new CppMemInit("m_scheduler", `std::make_shared<NapiScheduler>(${env})`)],
@@ -132,6 +144,7 @@ class NodeAddon extends CppClass {
                   .map(([name, val]) => `InstanceValue("${name}", ${val}, napi_enumerable),`)
                   .join("\n")}
                 InstanceMethod<&${this.name}::injectInjectables>("injectInjectables"),
+                InstanceMethod<&${this.name}::getPlatformScheduler>("getPlatformScheduler"),
             });
             `,
       }),

packages/realm/bindgen/src/templates/typescript.ts

@@ -187,6 +187,9 @@ export function generate({ rawSpec, spec: boundSpec, file }: TemplateContext): v
   out("export type AppError = Error & {code: number};");
   out("export type CppErrorCode = Error & {code: number, category: string};");
 
+  out("// Special functions");
+  out("export const getPlatformScheduler: undefined | (() => binding.SharedScheduler);");
+
   out(`
     // WeakRef polyfill for Hermes.
     export class WeakRef<T extends object> {

packages/realm/binding/node/napi_scheduler.cpp

@@ -57,7 +57,7 @@ NapiScheduler::NapiScheduler(Napi::Env& env)
 
 bool NapiScheduler::is_on_thread() const noexcept
 {
-    return false;
+    return m_id == std::this_thread::get_id();
 }
 
 bool NapiScheduler::is_same_as(const Scheduler* other) const noexcept

packages/realm/binding/node/napi_scheduler.h

@@ -23,6 +23,8 @@
 
 #include <napi.h>
 
+#include <thread>
+
 namespace realm::js::node {
 
 using VoidUniqueFunctionImpl = std::remove_pointer_t<decltype(realm::util::UniqueFunction<void()>().release())>;
@@ -38,6 +40,7 @@ class NapiScheduler : public realm::util::Scheduler {
 private:
     Napi::Env m_env;
     Napi::TypedThreadSafeFunction<std::nullptr_t, VoidUniqueFunctionImpl> m_tsf;
+    std::thread::id m_id = std::this_thread::get_id();
 };
 
 } // namespace realm::js::node

packages/realm/src/Realm.ts

@@ -455,6 +455,8 @@ export class Realm {
         syncConfig: config.sync ? toBindingSyncConfig(config.sync) : undefined,
         forceSyncHistory: config.openSyncedRealmLocally,
         automaticallyHandleBacklinksInMigrations: config.migrationOptions?.resolveEmbeddedConstraints ?? false,
+        // Use a platform-specific scheduler if the platform expose one
+        scheduler: binding.getPlatformScheduler ? binding.getPlatformScheduler() : undefined,
       },
     };
   }