Adding RequestHeadersComplete event for HTTPTransactionObserver

Summary: Add REQUEST_HEADERS_COMPLETE as a transaction byte event, to mark the start of an HTTP Request (corresponds to the HTTPSessionObserver RequestStart event)

Reviewed By: metaduc

Differential Revision:
D73543450

Privacy Context Container: L1201441

fbshipit-source-id: ef37fc212eb35919d27250e31d82851ed2af2619

Author: Sharad Jaiswal (Eng)

proxygen/lib/http/observer/HTTPTransactionObserverInterface.h

@@ -29,6 +29,7 @@ class HTTPTransactionObserverInterface {
 
   struct TxnBytesEvent {
     enum class Type : uint8_t {
+      REQUEST_HEADERS_COMPLETE,
       FIRST_HEADER_BYTE_WRITE,
       FIRST_BODY_BYTE_WRITE,
       FIRST_BODY_BYTE_ACK,

proxygen/lib/http/session/HTTPTransaction.cpp

@@ -252,6 +252,22 @@ void HTTPTransaction::onIngressHeadersComplete(
   if (transportCallback_) {
     transportCallback_->headerBytesReceived(msg->getIngressHeaderSize());
   }
+
+  if (txnObserverContainer_.hasObserversForEvent<
+          HTTPTransactionObserverInterface::Events::TxnBytes>()) {
+    const auto e =
+        HTTPTransactionObserverInterface::TxnBytesEvent::Builder()
+            .setTimestamp(proxygen::SteadyClock::now())
+            .setType(HTTPTransactionObserverInterface::TxnBytesEvent::Type::
+                         REQUEST_HEADERS_COMPLETE)
+            .build();
+    txnObserverContainer_.invokeInterfaceMethod<
+        HTTPTransactionObserverInterface::Events::TxnBytes>(
+        [&e](auto observer, auto observed) {
+          observer->onBytesEvent(observed, e);
+        });
+  }
+
   updateIngressCompressionInfo(transport_.getCodec().getCompressionInfo());
   if (mustQueueIngress()) {
     checkCreateDeferredIngress();