Ensure _sessions accessed only on one thread

plugins/bnet_plugin/bnet_plugin.cpp

@@ -1049,26 +1049,22 @@ namespace eosio {
 
    class bnet_plugin_impl : public std::enable_shared_from_this<bnet_plugin_impl> {
       public:
-         bnet_plugin_impl() {
-            _peer_pk = fc::crypto::private_key::generate();
-            _peer_id = _peer_pk.get_public_key();
-         }
-
-         string                                         _bnet_endpoint_address = "0.0.0.0";
-         uint16_t                                       _bnet_endpoint_port = 4321;
-         bool                                           _request_trx = true;
-         public_key_type                                _peer_id;
-         private_key_type                               _peer_pk; /// one time random key to identify this process
+         bnet_plugin_impl() = default;
 
+         const private_key_type  _peer_pk = fc::crypto::private_key::generate(); /// one time random key to identify this process
+         public_key_type         _peer_id = _peer_pk.get_public_key();
+         string                                                 _bnet_endpoint_address = "0.0.0.0";
+         uint16_t                                               _bnet_endpoint_port = 4321;
+         bool                                                   _request_trx = true;
 
-         std::vector<std::string>                       _connect_to_peers; /// list of peers to connect to
-         std::vector<std::thread>                       _socket_threads;
-         int32_t                                        _num_threads = 1;
-         std::unique_ptr<boost::asio::io_context>       _ioc; // lifetime guarded by shared_ptr of bnet_plugin_impl
-         std::shared_ptr<listener>                      _listener;
-         std::shared_ptr<boost::asio::deadline_timer>   _timer;
+         std::vector<std::string>                               _connect_to_peers; /// list of peers to connect to
+         std::vector<std::thread>                               _socket_threads;
+         int32_t                                                _num_threads = 1;
 
-         std::map<const session*, std::weak_ptr<session> > _sessions;
+         std::unique_ptr<boost::asio::io_context>               _ioc; // lifetime guarded by shared_ptr of bnet_plugin_impl
+         std::shared_ptr<listener>                              _listener;
+         std::shared_ptr<boost::asio::deadline_timer>           _timer;    // only access on app io_service
+         std::map<const session*, std::weak_ptr<session> >      _sessions; // only access on app io_service
 
          channels::irreversible_block::channel_type::handle     _on_irb_handle;
          channels::accepted_block::channel_type::handle         _on_accepted_block_handle;
@@ -1085,6 +1081,7 @@ namespace eosio {
          }
 
          void on_session_close( const session* s ) {
+            if( !app().get_io_service().get_executor().running_in_this_thread() ) { elog( "wrong strand"); }
             auto itr = _sessions.find(s);
             if( _sessions.end() != itr )
                _sessions.erase(itr);
@@ -1092,14 +1089,16 @@ namespace eosio {
 
          template<typename Call>
          void for_each_session( Call callback ) {
-            for( const auto& item : _sessions ) {
-               if( auto ses = item.second.lock() ) {
-                  ses->_ios.post( boost::asio::bind_executor(
-                                        ses->_strand,
-                                        [ses,cb=callback](){ cb(ses); }
-                                    ));
+            app().get_io_service().post([this, callback = callback] {
+               for (const auto& item : _sessions) {
+                  if (auto ses = item.second.lock()) {
+                     ses->_ios.post(boost::asio::bind_executor(
+                           ses->_strand,
+                           [ses, cb = callback]() { cb(ses); }
+                     ));
+                  }
                }
-            }
+            });
          }
 
          void on_accepted_transaction( transaction_metadata_ptr trx ) {
@@ -1146,6 +1145,7 @@ namespace eosio {
          };
 
          void on_reconnect_peers() {
+             if( !app().get_io_service().get_executor().running_in_this_thread() ) { elog( "wrong strand"); }
              for( const auto& peer : _connect_to_peers ) {
                 bool found = false;
                 for( const auto& con : _sessions ) {