Merge pull request #3797 from cloudflare/joshthoward/add-wae-output-gate

Add output gate for Workers Analytics Engine writes

Author: joshthoward

src/workerd/api/analytics-engine.c++

@@ -15,6 +15,21 @@ void AnalyticsEngine::writeDataPoint(
 
   context.getLimitEnforcer().newAnalyticsEngineRequest();
 
+  // Optimization: For non-actors, which never have output locks, avoid the overhead of
+  // awaitIo() and such by not going back to the event loop at all.
+  KJ_IF_SOME(promise, context.waitForOutputLocksIfNecessary()) {
+    context.awaitIo(js, kj::mv(promise), [this, event = kj::mv(event)](jsg::Lock& js) mutable {
+      writeDataPointNoOutputLock(js, kj::mv(event));
+    });
+  } else {
+    writeDataPointNoOutputLock(js, kj::mv(event));
+  }
+}
+
+void AnalyticsEngine::writeDataPointNoOutputLock(
+    jsg::Lock& js, jsg::Optional<api::AnalyticsEngine::AnalyticsEngineEvent>&& event) {
+  auto& context = IoContext::current();
+
   context.writeLogfwdr(logfwdrChannel, [&](capnp::AnyPointer::Builder ptr) {
     api::AnalyticsEngineEvent::Builder aeEvent = ptr.initAs<api::AnalyticsEngineEvent>();
 

src/workerd/api/analytics-engine.h

@@ -70,6 +70,10 @@ class AnalyticsEngine: public jsg::Object {
     return m * 1000000;
   }
 
+  // Called within writeDataPoint after waiting for output locks
+  void writeDataPointNoOutputLock(
+      jsg::Lock& js, jsg::Optional<api::AnalyticsEngine::AnalyticsEngineEvent>&& event);
+
   uint logfwdrChannel;
   kj::String dataset;
   int64_t version;