Implement local connection for perf metrics in HostTarget (#52838)

Summary:
Pull Request resolved: #52838

**Context**

Experimental V2 Performance Monitor prototype, beginning by bringing the [Interaction to Next Paint (INP)](https://web.dev/articles/inp) metric to React Native.

**This diff**

Wires up a client/subscriber for the `"__chromium_devtools_metrics_reporter"` runtime binding (to which we emit live metrics events since D78904748). This will be used to unpack these performance updates to send to the host platform.

- Creates a new `HostRuntimeBinding` helper, which establishes a local/private CDP session.
- Conditionally installs our perf metrics runtime binding in `HostTarget` when `perfMonitorV2Enabled` is set.
- Wires up a new `onPerfMonitorUpdate` event on `HostTargetDelegate` (unimplemented until the next diff).

Changelog: [Internal]

Reviewed By: hoxyq

Differential Revision: D78904766

Author: huntie

packages/react-native/ReactAndroid/src/main/jni/react/runtime/jni/JReactHostInspectorTarget.cpp

@@ -127,6 +127,9 @@ void JReactHostInspectorTarget::onSetPausedInDebuggerMessage(
   }
 }
 
+void JReactHostInspectorTarget::unstable_onPerfMonitorUpdate(
+    const PerfMonitorUpdateRequest& /* unused */) {}
+
 void JReactHostInspectorTarget::loadNetworkResource(
     const jsinspector_modern::LoadNetworkResourceRequest& params,
     jsinspector_modern::ScopedExecutor<

packages/react-native/ReactAndroid/src/main/jni/react/runtime/jni/JReactHostInspectorTarget.h

@@ -84,6 +84,8 @@ class JReactHostInspectorTarget
   void onReload(const PageReloadRequest& request) override;
   void onSetPausedInDebuggerMessage(
       const OverlaySetPausedInDebuggerMessageRequest&) override;
+  void unstable_onPerfMonitorUpdate(
+      const PerfMonitorUpdateRequest& /* unused */) override;
   void loadNetworkResource(
       const jsinspector_modern::LoadNetworkResourceRequest& params,
       jsinspector_modern::ScopedExecutor<

packages/react-native/ReactCommon/jsinspector-modern/HostTarget.cpp

@@ -145,11 +145,53 @@ class HostCommandSender {
   std::unique_ptr<ILocalConnection> connection_;
 };
 
+/**
+ * Enables the caller to install and subscribe to a named CDP runtime binding
+ * on the HostTarget via a callback. Note: Per CDP spec, this does not need to
+ * check if the `Runtime` domain is enabled.
+ */
+class HostRuntimeBinding {
+ public:
+  explicit HostRuntimeBinding(
+      HostTarget& target,
+      std::string name,
+      std::function<void(std::string)> callback)
+      : connection_(target.connect(std::make_unique<CallbackRemoteConnection>(
+            [callback = std::move(callback)](const std::string& message) {
+              auto parsedMessage = folly::parseJson(message);
+
+              // Ignore initial Runtime.addBinding response
+              if (parsedMessage["id"] == 0 &&
+                  parsedMessage["result"].isObject() &&
+                  parsedMessage["result"].empty()) {
+                return;
+              }
+
+              // Assert that we only intercept bindingCalled responses
+              assert(
+                  parsedMessage["method"].asString() ==
+                  "Runtime.bindingCalled");
+              callback(parsedMessage["params"]["payload"].asString());
+            }))) {
+    // Install runtime binding
+    connection_->sendMessage(cdp::jsonRequest(
+        0,
+        "Runtime.addBinding",
+        folly::dynamic::object("name", std::move(name))));
+  }
+
+ private:
+  std::unique_ptr<ILocalConnection> connection_;
+};
+
 std::shared_ptr<HostTarget> HostTarget::create(
     HostTargetDelegate& delegate,
     VoidExecutor executor) {
   std::shared_ptr<HostTarget> hostTarget{new HostTarget(delegate)};
   hostTarget->setExecutor(std::move(executor));
+  if (InspectorFlags::getInstance().getPerfMonitorV2Enabled()) {
+    hostTarget->installPerfMetricsBinding();
+  }
   return hostTarget;
 }
 
@@ -212,6 +254,19 @@ void HostTarget::sendCommand(HostCommand command) {
   });
 }
 
+void HostTarget::installPerfMetricsBinding() {
+  perfMetricsBinding_ = std::make_unique<HostRuntimeBinding>(
+      *this, // Used immediately
+      "__chromium_devtools_metrics_reporter",
+      [this](const std::string& message) {
+        auto payload = folly::parseJson(message);
+        HostTargetDelegate::PerfMonitorUpdateRequest request{
+            .interactionName = payload["eventName"].asString(),
+            .durationMs = static_cast<uint16_t>(payload["duration"].asInt())};
+        delegate_.unstable_onPerfMonitorUpdate(request);
+      });
+}
+
 HostTargetController::HostTargetController(HostTarget& target)
     : target_(target) {}
 

packages/react-native/ReactCommon/jsinspector-modern/HostTarget.h

@@ -35,6 +35,7 @@ namespace facebook::react::jsinspector_modern {
 class HostTargetSession;
 class HostAgent;
 class HostCommandSender;
+class HostRuntimeBinding;
 class HostTarget;
 
 struct HostTargetMetadata {
@@ -93,6 +94,11 @@ class HostTargetDelegate : public LoadNetworkResourceDelegate {
     }
   };
 
+  struct PerfMonitorUpdateRequest {
+    std::string interactionName;
+    uint16_t durationMs;
+  };
+
   virtual ~HostTargetDelegate() override;
 
   /**
@@ -121,6 +127,13 @@ class HostTargetDelegate : public LoadNetworkResourceDelegate {
   virtual void onSetPausedInDebuggerMessage(
       const OverlaySetPausedInDebuggerMessageRequest& request) = 0;
 
+  /**
+   * [Experimental] Called when the runtime has new data for the V2 Perf
+   * Monitor overlay. This is called on the inspector thread.
+   */
+  virtual void unstable_onPerfMonitorUpdate(
+      const PerfMonitorUpdateRequest& /*request*/) {}
+
   /**
    * Called by NetworkIOAgent on handling a `Network.loadNetworkResource` CDP
    * request. Platform implementations should override this to perform a
@@ -256,6 +269,7 @@ class JSINSPECTOR_EXPORT HostTarget
   std::shared_ptr<ExecutionContextManager> executionContextManager_;
   std::shared_ptr<InstanceTarget> currentInstance_{nullptr};
   std::unique_ptr<HostCommandSender> commandSender_;
+  std::unique_ptr<HostRuntimeBinding> perfMetricsBinding_;
 
   inline HostTargetDelegate& getDelegate() {
     return delegate_;
@@ -265,6 +279,13 @@ class JSINSPECTOR_EXPORT HostTarget
     return currentInstance_ != nullptr;
   }
 
+  /**
+   * Install a runtime binding subscribing to the Interaction to Next Paint
+   * (INP) live metric, which we broadcast to the V2 Perf Monitor overlay
+   * via \ref HostTargetDelegate::unstable_onPerfMonitorUpdate.
+   */
+  void installPerfMetricsBinding();
+
   // Necessary to allow HostAgent to access HostTarget's internals in a
   // controlled way (i.e. only HostTargetController gets friend access, while
   // HostAgent itself doesn't).

packages/react-native/ReactCommon/jsinspector-modern/InspectorFlags.cpp

@@ -33,6 +33,10 @@ bool InspectorFlags::getNetworkInspectionEnabled() const {
   return loadFlagsAndAssertUnchanged().networkInspectionEnabled;
 }
 
+bool InspectorFlags::getPerfMonitorV2Enabled() const {
+  return loadFlagsAndAssertUnchanged().perfMonitorV2Enabled;
+}
+
 void InspectorFlags::dangerouslyResetFlags() {
   *this = InspectorFlags{};
 }
@@ -59,6 +63,9 @@ const InspectorFlags::Values& InspectorFlags::loadFlagsAndAssertUnchanged()
       .networkInspectionEnabled =
           ReactNativeFeatureFlags::enableBridgelessArchitecture() &&
           ReactNativeFeatureFlags::fuseboxNetworkInspectionEnabled(),
+      .perfMonitorV2Enabled =
+          ReactNativeFeatureFlags::enableBridgelessArchitecture() &&
+          ReactNativeFeatureFlags::perfMonitorV2Enabled(),
   };
 
   if (cachedValues_.has_value() && !inconsistentFlagsStateLogged_) {

packages/react-native/ReactCommon/jsinspector-modern/InspectorFlags.h

@@ -35,6 +35,11 @@ class InspectorFlags {
    */
   bool getNetworkInspectionEnabled() const;
 
+  /**
+   * Flag determining if the V2 in-app Performance Monitor is enabled.
+   */
+  bool getPerfMonitorV2Enabled() const;
+
   /**
    * Forcibly disable the main `getFuseboxEnabled()` flag. This should ONLY be
    * used by `ReactInstanceIntegrationTest`.
@@ -52,6 +57,7 @@ class InspectorFlags {
     bool fuseboxEnabled;
     bool isProfilingBuild;
     bool networkInspectionEnabled;
+    bool perfMonitorV2Enabled;
     bool operator==(const Values&) const = default;
   };
 

packages/react-native/ReactCommon/jsinspector-modern/InspectorUtilities.cpp

@@ -24,6 +24,14 @@ void CallbackLocalConnection::disconnect() {
   handler_ = nullptr;
 }
 
+CallbackRemoteConnection::CallbackRemoteConnection(
+    std::function<void(std::string)> handler)
+    : handler_(std::move(handler)) {}
+
+void CallbackRemoteConnection::onMessage(std::string message) {
+  handler_(std::move(message));
+}
+
 RAIIRemoteConnection::RAIIRemoteConnection(
     std::unique_ptr<IRemoteConnection> remote)
     : remote_(std::move(remote)) {}

packages/react-native/ReactCommon/jsinspector-modern/InspectorUtilities.h

@@ -33,6 +33,25 @@ class CallbackLocalConnection : public ILocalConnection {
   std::function<void(std::string)> handler_;
 };
 
+/**
+ * Wraps a callback function in IRemoteConnection.
+ */
+class CallbackRemoteConnection : public IRemoteConnection {
+ public:
+  /**
+   * Creates a new Connection that uses the given callback to receive messages
+   * from the backend.
+   */
+  explicit CallbackRemoteConnection(std::function<void(std::string)> handler);
+
+  void onMessage(std::string message) override;
+
+  void onDisconnect() override {}
+
+ private:
+  std::function<void(std::string)> handler_;
+};
+
 /**
  * Wraps an IRemoteConnection in a simpler interface that calls `onDisconnect`
  * implicitly upon destruction.