Add ConnsTLSAccepted metric

Summary: Reimplement D79220681 using the new `ServerObserver`.

Reviewed By: podtserkovskiy

Differential Revision: D83169371

fbshipit-source-id: 0f1fc1f9306fdcb00c179c787f0853ec7bae373f

Author: echistyakov

thrift/lib/go/thrift/rocket_server_transport.go

@@ -114,6 +114,7 @@ func (r *rocketServerTransport) acceptLoop(ctx context.Context) error {
 			// Read/Write calls - so that we can access ALPN value and choose the transport.
 			tlsConn, isTLS := conn.(tlsConnectionStaterHandshaker)
 			if isTLS {
+				r.observer.ConnTLSAccepted()
 				r.stats.ConnsTLS.RecordEvent()
 
 				err = tlsConn.HandshakeContext(ctx)

thrift/lib/go/thrift/server_observer.go

@@ -22,8 +22,9 @@ import "time"
 // for monitoring and troubleshooting purposes.
 type ServerObserver interface {
 	// Connection lifecycle events
-	ConnDropped()  // server-initiated connection close
-	ConnAccepted() // new connection successfully accepted
+	ConnDropped()     // server-initiated connection close
+	ConnAccepted()    // new connection successfully accepted
+	ConnTLSAccepted() // new TLS connection successfully accepted
 
 	// Request processing events
 	TaskKilled()                    // request rejected due to parsing errors or shutdown

thrift/lib/go/thrift/server_observer_noop.go

@@ -34,8 +34,9 @@ func newNoopServerObserver() ServerObserver {
 // All methods are no-op implementations
 
 // Connection lifecycle events
-func (*noopServerObserver) ConnDropped()  {}
-func (*noopServerObserver) ConnAccepted() {}
+func (*noopServerObserver) ConnDropped()     {}
+func (*noopServerObserver) ConnAccepted()    {}
+func (*noopServerObserver) ConnTLSAccepted() {}
 
 // Request processing events
 func (*noopServerObserver) TaskKilled()          {}

thrift/lib/go/thrift/server_observer_noop_test.go

@@ -31,6 +31,8 @@ func TestNoopServerObserver(t *testing.T) {
 
 	// Test that all methods can be called without panicking
 	observer.ConnDropped()
+	observer.ConnAccepted()
+	observer.ConnTLSAccepted()
 	observer.TaskKilled()
 	observer.TaskTimeout()
 	observer.DeclaredException()
@@ -39,6 +41,5 @@ func TestNoopServerObserver(t *testing.T) {
 	observer.ReceivedRequest()
 	observer.SentReply()
 	observer.ActiveRequests(10)
-	observer.ConnAccepted()
 	observer.ProcessTime(200 * time.Millisecond)
 }