relay: make stop() idempotent and keep context_ alive during teardown

src/MoqxPicoRelayServer.cpp

@@ -93,12 +93,14 @@ MoqxPicoRelayServer::~MoqxPicoRelayServer() {
 }
 
 void MoqxPicoRelayServer::stop() {
-  if (!context_) {
+  if (stopped_) {
     return;
   }
+  stopped_ = true;
+  // Keep context_ alive: terminateClientSession can run after stop() returns,
+  // from handleClientSession coroutines still draining on the evb.
   context_->stop();
   evb_->runImmediatelyOrRunInEventBaseThreadAndWait([this] { MoQPicoQuicEventBaseServer::stop(); });
-  context_.reset();
 }
 
 void MoqxPicoRelayServer::setStatsRegistry(std::shared_ptr<stats::StatsRegistry> registry) {

src/MoqxPicoRelayServer.h

@@ -64,6 +64,7 @@ class MoqxPicoRelayServer : public moxygen::MoQPicoQuicEventBaseServer {
   config::ListenerConfig listenerCfg_;
   std::shared_ptr<MoqxRelayContext> context_;
   folly::EventBase* evb_;
+  bool stopped_{false};
 };
 
 } // namespace openmoq::moqx

src/MoqxRelayServer.cpp

@@ -143,12 +143,13 @@ MoqxRelayServer::~MoqxRelayServer() {
 }
 
 void MoqxRelayServer::stop() {
-  if (!context_) {
+  if (stopped_) {
     return;
   }
-  // QuicServer::shutdown drives terminateClientSession, which uses context_.
+  stopped_ = true;
+  // Keep context_ alive: terminateClientSession can run after stop() returns,
+  // from handleClientSession coroutines still draining on IO threads.
   MoQServer::stop();
-  context_.reset();
 }
 
 void MoqxRelayServer::setStatsRegistry(std::shared_ptr<stats::StatsRegistry> registry) {

src/MoqxRelayServer.h

@@ -57,6 +57,7 @@ class MoqxRelayServer : public moxygen::MoQServer {
   config::ListenerConfig listenerCfg_;
   std::shared_ptr<MoqxRelayContext> context_;
   folly::IOThreadPoolExecutor* ioExecutor_;
+  bool stopped_{false};
 };
 
 } // namespace openmoq::moqx