diff --git a/proxygen/lib/http/session/HQSession.cpp b/proxygen/lib/http/session/HQSession.cpp
index 01aab8ebd..f84483608 100644
--- a/proxygen/lib/http/session/HQSession.cpp
+++ b/proxygen/lib/http/session/HQSession.cpp
@@ -3906,4 +3906,33 @@ std::ostream& operator<<(std::ostream& os, const HQSession& session) {
   return os;
 }
 
+std::ostream& operator<<(std::ostream& os, HQSession::DrainState drainState) {
+  switch (drainState) {
+    case HQSession::DrainState::NONE:
+      os << "none";
+      break;
+    case HQSession::DrainState::PENDING:
+      os << "pending";
+      break;
+    case HQSession::DrainState::CLOSE_SENT:
+      os << "close_sent";
+      break;
+    case HQSession::DrainState::CLOSE_RECEIVED:
+      os << "close_recvd";
+      break;
+    case HQSession::DrainState::FIRST_GOAWAY:
+      os << "first_goaway";
+      break;
+    case HQSession::DrainState::SECOND_GOAWAY:
+      os << "second_goaway";
+      break;
+    case HQSession::DrainState::DONE:
+      os << "done";
+      break;
+    default:
+      folly::assume_unreachable();
+  }
+  return os;
+}
+
 } // namespace proxygen
diff --git a/proxygen/lib/http/session/HQSession.h b/proxygen/lib/http/session/HQSession.h
index ba27794d1..f536bffe8 100644
--- a/proxygen/lib/http/session/HQSession.h
+++ b/proxygen/lib/http/session/HQSession.h
@@ -267,6 +267,7 @@ class HQSession
          << ", local=" << getLocalAddress() << ", " << getPeerAddress()
          << "=upstream";
     }
+    os << ", drain=" << drainState_;
   }
 
   void onGoaway(uint64_t lastGoodStreamID,
@@ -2235,6 +2236,11 @@ class HQSession
   // NOTE: introduce better decoupling between the streams
   // and the containing session, then remove the friendship.
   friend class HQStreamBase;
+
+  // To let the operator<< access DrainState which is private
+  friend std::ostream& operator<<(std::ostream&, DrainState);
 }; // HQSession
 
+std::ostream& operator<<(std::ostream& os, HQSession::DrainState drainState);
+
 } // namespace proxygen