move cwnd blocked trace from Cubic to QuicTransportFunction

Summary:
So this trace is shared by all CongestionControllers. This also
changes what we log into the trace.

Reviewed By: siyengar

Differential Revision: D15184916

fbshipit-source-id: 6cbeb02ee2d24a6bf8d705ff883f5a57603988e7

quic/QuicConstants.h

@@ -229,6 +229,8 @@ constexpr std::chrono::microseconds::rep kPersistentCongestionThreshold = 3;
 constexpr std::chrono::microseconds::rep kPersistentCongestionPeriodFactor =
     (((std::chrono::microseconds::rep)1 << kPersistentCongestionThreshold) - 1);
 enum class CongestionControlType : uint8_t { Cubic, NewReno, Copa, BBR, None };
+// This is an approximation of a small enough number for cwnd to be blocked.
+constexpr size_t kBlockedSizeBytes = 20;
 
 constexpr uint64_t kInitCwndInMss = 10;
 constexpr uint64_t kMinCwndInMss = 2;

quic/api/QuicTransportFunctions.cpp

@@ -348,6 +348,14 @@ void updateConnection(
   conn.lossState.largestSent = std::max(conn.lossState.largestSent, packetNum);
   if (conn.congestionController && !pureAck) {
     conn.congestionController->onPacketSent(pkt);
+    // An approximation of the app being blocked. The app
+    // technically might not have bytes to write.
+    auto writableBytes = conn.congestionController->getWritableBytes();
+    bool cwndBlocked = writableBytes < kBlockedSizeBytes;
+    if (cwndBlocked) {
+      auto cwndBytes = conn.congestionController->getCongestionWindow();
+      QUIC_TRACE(cwnd_may_block, conn, writableBytes, cwndBytes);
+    }
   }
   if (pkt.isHandshake) {
     ++conn.outstandingHandshakePacketsCount;

quic/api/test/QuicTransportTest.cpp

@@ -358,11 +358,8 @@ TEST_F(QuicTransportTest, WriteDataWithProbing) {
   loopForWrites();
   // Pending numProbePackets is cleared:
   EXPECT_EQ(0, conn.pendingEvents.numProbePackets);
-  // getWritableBytes should be called with the same times as write
+  // both write and onPacketSent will inquire getWritableBytes
-  // getWritableBytes should happen exact one less time than socket write and
+  EXPECT_EQ(onPacketSentCounter + socketWriteCounter, getWritableBytesCounter);
-  // onPacketSent on write path and one more time in the updateWriteLooper.
-  EXPECT_EQ(socketWriteCounter, getWritableBytesCounter);
-  EXPECT_EQ(onPacketSentCounter, getWritableBytesCounter);
   transport_->close(folly::none);
 }
 

quic/congestion_control/QuicCubic.cpp

@@ -10,13 +10,6 @@
 #include <quic/congestion_control/CongestionControlFunctions.h>
 #include <quic/state/QuicStateFunctions.h>
 
-namespace {
-
-// This is an approximation of a small enough number
-// for cwnd to be blocked.
-constexpr size_t kBlockedSizeBytes = 20;
-}
-
 namespace quic {
 
 Cubic::Cubic(
@@ -89,17 +82,6 @@ void Cubic::onPacketSent(const OutstandingPacket& packet) {
         LocalErrorCode::INFLIGHT_BYTES_OVERFLOW);
   }
   inflightBytes_ += packet.encodedSize;
-  // An approximation of the app being blocked. The app
-  // technically might not have bytes to write.
-  bool cwndBlocked = getWritableBytes() < kBlockedSizeBytes;
-  if (cwndBlocked) {
-    QUIC_TRACE(
-        cubic_may_block,
-        conn_,
-        cubicStateToString(state_).data(),
-        cwndBytes_,
-        inflightBytes_);
-  }
 }
 
 void Cubic::onPacketLoss(const LossEvent& loss) {