Use separate flags to enable app data sent callbacks

Summary:
Previously we were using a single flag appDataSentEvents to enable 3 callbacks
(startWritingFromAppLimited, packetsWritten and appRateLimited). This commit
creates separate flags to enable each of these callbacks, we have use-cases
where Observers might want only packetsWritten events and not the others.

Also, this commit refactors the logic to deliver these 3 callbacks to all
observers into a separate method so they can be unit tested easily.

Reviewed By: bschlinker

Differential Revision: D27925011

fbshipit-source-id: 7f7436dfc3d50c3abcb8ec121b221d20e30b0c4b

quic/api/Observer.h

@@ -34,30 +34,36 @@ class Observer {
    * Specifies events observer wants to receive.
    */
   struct Config {
+    virtual ~Config() = default;
+
     // following flags enable support for various callbacks.
     // observer and socket lifecycle callbacks are always enabled.
     bool evbEvents{false};
-    bool appDataSentEvents{false};
-    bool appLimitedEvents{false};
+    bool packetsWrittenEvents{false};
+    bool appRateLimitedEvents{false};
     bool lossEvents{false};
     bool spuriousLossEvents{false};
     bool pmtuEvents{false};
     bool rttSamples{false};
     bool knobFrameEvents{false};
 
+    virtual void enableAllEvents() {
+      evbEvents = true;
+      packetsWrittenEvents = true;
+      appRateLimitedEvents = true;
+      rttSamples = true;
+      lossEvents = true;
+      spuriousLossEvents = true;
+      pmtuEvents = true;
+      knobFrameEvents = true;
+    }
+
     /**
      * Returns a config where all events are enabled.
      */
     static Config getConfigAllEventsEnabled() {
       Config config = {};
-      config.evbEvents = true;
-      config.appDataSentEvents = true;
-      config.appLimitedEvents = true;
-      config.rttSamples = true;
-      config.lossEvents = true;
-      config.spuriousLossEvents = true;
-      config.pmtuEvents = true;
-      config.knobFrameEvents = true;
+      config.enableAllEvents();
       return config;
     }
   };

quic/api/QuicTransportBase.cpp

@@ -2726,13 +2726,7 @@ void QuicTransportBase::writeSocketData() {
     auto packetsBefore = conn_->outstandings.numOutstanding();
     // Signal Observers the POTENTIAL start of a Write Block.
     if (conn_->waitingForAppData && conn_->congestionController) {
-      Observer::AppLimitedEvent startWritingFromAppLimitedEvent(
-          conn_->outstandings.packets, conn_->writeCount);
-      for (const auto& cb : *observers_) {
-        if (cb->getConfig().appDataSentEvents) {
-          cb->startWritingFromAppLimited(this, startWritingFromAppLimitedEvent);
-        }
-      }
+      notifyStartWritingFromAppRateLimited();
       conn_->waitingForAppData = false;
     }
     writeData();
@@ -2749,13 +2743,7 @@ void QuicTransportBase::writeSocketData() {
       // These may/may not be app data packets, it it up to the Observers
       // to deal with these packets.
       if (packetWritten && conn_->congestionController) {
-        Observer::AppLimitedEvent packetsWrittenEvent(
-            conn_->outstandings.packets, conn_->writeCount);
-        for (const auto& cb : *observers_) {
-          if (cb->getConfig().appDataSentEvents) {
-            cb->packetsWritten(this, packetsWrittenEvent);
-          }
-        }
+        notifyPacketsWritten();
       }
       if (conn_->loopDetectorCallback && packetWritten) {
         conn_->writeDebugState.currentEmptyLoopCount = 0;
@@ -2792,13 +2780,7 @@ void QuicTransportBase::writeSocketData() {
         conn_->congestionController->setAppLimited();
         // notify via connection call and any observer callbacks
         connCallback_->onAppRateLimited();
-        Observer::AppLimitedEvent appLimitedEvent(
-            conn_->outstandings.packets, conn_->writeCount);
-        for (const auto& cb : *observers_) {
-          if (cb->getConfig().appLimitedEvents) {
-            cb->appRateLimited(this, appLimitedEvent);
-          }
-        }
+        notifyAppRateLimited();
         conn_->waitingForAppData = true;
       }
     }
@@ -3237,4 +3219,34 @@ QuicSocket::WriteResult QuicTransportBase::setDSRPacketizationRequestSender(
   return folly::unit;
 }
 
+void QuicTransportBase::notifyStartWritingFromAppRateLimited() {
+  Observer::AppLimitedEvent startWritingFromAppLimitedEvent(
+      conn_->outstandings.packets, conn_->writeCount);
+  for (const auto& cb : *observers_) {
+    if (cb->getConfig().appRateLimitedEvents) {
+      cb->startWritingFromAppLimited(this, startWritingFromAppLimitedEvent);
+    }
+  }
+}
+
+void QuicTransportBase::notifyPacketsWritten() {
+  Observer::AppLimitedEvent packetsWrittenEvent(
+      conn_->outstandings.packets, conn_->writeCount);
+  for (const auto& cb : *observers_) {
+    if (cb->getConfig().packetsWrittenEvents) {
+      cb->packetsWritten(this, packetsWrittenEvent);
+    }
+  }
+}
+
+void QuicTransportBase::notifyAppRateLimited() {
+  Observer::AppLimitedEvent appRateLimitedEvent(
+      conn_->outstandings.packets, conn_->writeCount);
+  for (const auto& cb : *observers_) {
+    if (cb->getConfig().appRateLimitedEvents) {
+      cb->appRateLimited(this, appRateLimitedEvent);
+    }
+  }
+}
+
 } // namespace quic

quic/api/QuicTransportBase.h

@@ -718,6 +718,12 @@ class QuicTransportBase : public QuicSocket {
 
   void validateCongestionAndPacing(CongestionControlType& type);
 
+  // Helpers to notify all registered observers about specific events during
+  // socket write (if enabled in the observer's config).
+  void notifyStartWritingFromAppRateLimited();
+  void notifyPacketsWritten();
+  void notifyAppRateLimited();
+
   /**
    * Callback when we receive a transport knob
    */

quic/api/test/QuicTransportTest.cpp

@@ -357,8 +357,8 @@ TEST_F(QuicTransportTest, NotAppLimitedWithNoWritableBytesWithObservers) {
       }));
 
   Observer::Config config = {};
-  config.appLimitedEvents = true;
-  config.appDataSentEvents = true;
+  config.packetsWrittenEvents = true;
+  config.appRateLimitedEvents = true;
   auto cb = std::make_unique<StrictMock<MockObserver>>(config);
 
   EXPECT_CALL(*cb, observerAttach(transport_.get()));
@@ -390,8 +390,8 @@ TEST_F(QuicTransportTest, NotAppLimitedWithLargeBufferWithObservers) {
       .WillRepeatedly(Return(5000));
 
   Observer::Config config = {};
-  config.appLimitedEvents = true;
-  config.appDataSentEvents = true;
+  config.packetsWrittenEvents = true;
+  config.appRateLimitedEvents = true;
   auto cb = std::make_unique<StrictMock<MockObserver>>(config);
 
   EXPECT_CALL(*cb, observerAttach(transport_.get()));
@@ -414,8 +414,8 @@ TEST_F(QuicTransportTest, NotAppLimitedWithLargeBufferWithObservers) {
 
 TEST_F(QuicTransportTest, AppLimitedWithObservers) {
   Observer::Config config = {};
-  config.appLimitedEvents = true;
-  config.appDataSentEvents = true;
+  config.packetsWrittenEvents = true;
+  config.appRateLimitedEvents = true;
   auto cb1 = std::make_unique<StrictMock<MockObserver>>(config);
   auto cb2 = std::make_unique<StrictMock<MockObserver>>(config);
   EXPECT_CALL(*cb1, observerAttach(transport_.get()));

quic/api/test/TestQuicTransport.h

@@ -132,6 +132,18 @@ class TestQuicTransport
     setIdleTimer();
   }
 
+  void invokeNotifyStartWritingFromAppRateLimited() {
+    notifyStartWritingFromAppRateLimited();
+  }
+
+  void invokeNotifyPacketsWritten() {
+    notifyPacketsWritten();
+  }
+
+  void invokeNotifyAppRateLimited() {
+    notifyAppRateLimited();
+  }
+
   std::unique_ptr<Aead> aead;
   std::unique_ptr<PacketNumberCipher> headerCipher;
   bool closed{false};

quic/tools/tperf/tperf.cpp

@@ -194,7 +194,7 @@ class TPerfAcceptObserver : public AcceptObserver {
     // Create an observer config, only enabling events we are interested in
     // receiving.
     Observer::Config config = {};
-    config.appLimitedEvents = true;
+    config.appRateLimitedEvents = true;
     config.pmtuEvents = true;
     config.rttSamples = true;
     config.lossEvents = true;