Add tracing spans for input gate hold

Author: shrima-cf

src/workerd/io/io-context.h

@@ -30,6 +30,7 @@
 namespace workerd {
 class WorkerTracer;
 class BaseTracer;
+class Worker;
 }  // namespace workerd
 
 namespace workerd {
@@ -176,6 +177,14 @@ class IoContext_IncomingRequest final {
 
   SpanParent getCurrentUserTraceSpan();
 
+  void startInputGateHoldSpan() {
+    inputGateHoldSpan = getMetrics().getSpan().newChild("actor_input_gate_hold"_kjc);
+  }
+
+  void stopInputGateHoldSpan() {
+    inputGateHoldSpan = kj::none;
+  }
+
   // The invocation span context is a unique identifier for a specific
   // worker invocation.
   tracing::InvocationSpanContext& getInvocationSpanContext();
@@ -211,6 +220,8 @@ class IoContext_IncomingRequest final {
   // Tracks the location where delivered() was called for debugging.
   kj::Maybe<kj::SourceLocation> deliveredLocation;
 
+  kj::Maybe<SpanBuilder> inputGateHoldSpan;
+
   friend class IoContext;
 };
 
@@ -1141,6 +1152,7 @@ class IoContext final: public kj::Refcounted, private kj::TaskSet::ErrorHandler
 
   friend class Finalizeable;
   friend class DeleteQueue;
+  friend class Worker;
   template <typename T>
   friend kj::Promise<ExceptionOr<T>> promiseForExceptionOrT(kj::Promise<T> promise);
   template <typename Result>

src/workerd/io/worker.c++

@@ -3441,9 +3441,15 @@ struct Worker::Actor::Impl {
 
     void inputGateLocked() override {
       metrics.inputGateLocked();
+      KJ_IF_SOME(ctx, getIoContext()) {
+        ctx.getCurrentIncomingRequest().startInputGateHoldSpan();
+      }
     }
     void inputGateReleased() override {
       metrics.inputGateReleased();
+      KJ_IF_SOME(ctx, getIoContext()) {
+        ctx.getCurrentIncomingRequest().stopInputGateHoldSpan();
+      }
     }
     void inputGateWaiterAdded() override {
       metrics.inputGateWaiterAdded();
@@ -3490,12 +3496,17 @@ struct Worker::Actor::Impl {
       metrics.storageWriteCompleted(latency);
     }
 
+    void setIoContext(IoContext& ctx) { ioContext = ctx; }
+    kj::Maybe<IoContext&> getIoContext() { return ioContext; }
+
    private:
     kj::Own<Loopback> loopback;  // only for updateAlarmInMemory()
     TimerChannel& timerChannel;  // only for afterLimitTimeout() and updateAlarmInMemory()
     ActorObserver& metrics;
 
     kj::Maybe<kj::Promise<void>> maybeAlarmPreviewTask;
+
+    kj::Maybe<IoContext&> ioContext = kj::none;
   };
 
   HooksImpl hooks;
@@ -4053,6 +4064,7 @@ void Worker::Actor::setIoContext(kj::Own<IoContext> context) {
     impl->abortFulfiller = kj::none;
   }
   auto& limitEnforcer = context->getLimitEnforcer();
+  impl->hooks.setIoContext(*context);
   impl->ioContext = kj::mv(context);
   impl->metricsFlushLoopTask =
       impl->metrics->flushLoop(impl->timerChannel, limitEnforcer)