application啟動插件的流程：

step1. 調用各個插件的initialize()
step2. 調用各個插件的initialize_logging();
step3. 調用各個插件的startup()
step4. exec()

1. initialize

programs\EOS\main.cpp

int main(int argc, char** argv) {try { if(!app().initialize<chain_plugin, chain_api_plugin, http_plugin, history_plugin, history_api_plugin, net_plugin, maker_plugin, maker_api_plugin>(argc, argv)) {class application{bool initialize(int argc, char** argv) {return initialize_impl(argc, argv, {find_plugin<Plugin>()...});}bool application::initialize_impl(int argc, char** argv, vector<abstract_plugin*> autostart_plugins) {set_program_options();try {for (auto plugin : autostart_plugins)if (plugin != nullptr && plugin->get_state() == abstract_plugin::registered)plugin->initialize(options);

1.1. abstract_plugin 類

包含四個狀態： 已注冊、 已初始化、 已啟動、 已停止。

class abstract_plugin {public:enum state {registered, ///< the plugin is constructed but doesn't do anythinginitialized, ///< the plugin has initialized any state required but is idlestarted, ///< the plugin is actively runningstopped ///< the plugin is no longer running};virtual ~abstract_plugin(){}virtual state get_state()const = 0;virtual const std::string& name()const = 0;virtual void set_program_options( options_description& cli, options_description& cfg ) = 0;virtual void initialize(const variables_map& options) = 0;virtual void handle_sighup() = 0;virtual void startup() = 0;virtual void shutdown() = 0;}; template<typename Impl> class plugin : public abstract_plugin {public:plugin():_name(boost::core::demangle(typeid(Impl).name())){}virtual ~plugin(){}virtual state get_state()const override { return _state; }virtual const std::string& name()const override { return _name; }virtual void register_dependencies() {static_cast<Impl*>(this)->plugin_requires([&](auto& plug){});}virtual void initialize(const variables_map& options) override {if(\_state == registered) {\_state = initialized;//分步初始化，第二步static_cast<Impl*>(this)->plugin_requires([&](auto& plug){ plug.initialize(options); });//初始化此插件依賴的插件,并遞歸調用依賴插件static_cast<Impl*>(this)->plugin_initialize(options); //初始化插件//ilog( "initializing plugin ${name}", ("name",name()) );app().plugin_initialized(*this);//保存啟動的插件}assert(\_state == initialized); /// if initial state was not registered, final state cannot be initiaized}virtual void handle_sighup() override {}virtual void startup() override {if(_state == initialized) {_state = started;static_cast<Impl*>(this)->plugin_requires([&](auto& plug){ plug.startup(); });static_cast<Impl*>(this)->plugin_startup();app().plugin_started(*this);}assert(_state == started); // if initial state was not initialized, final state cannot be started}virtual void shutdown() override {if(_state == started) {_state = stopped;//ilog( "shutting down plugin ${name}", ("name",name()) );static_cast<Impl*>(this)->plugin_shutdown();}}protected:plugin(const string& name) : _name(name){}private:state _state = abstract_plugin::registered;std::string _name;};

2. startup

void application::startup() {//during startup, run a second thread to catch SIGINT/SIGTERM/SIGPIPE/SIGHUPboost::asio::io_service startup_thread_ios;setup_signal_handling_on_ios(startup_thread_ios, true);std::thread startup_thread([&startup_thread_ios]() {startup_thread_ios.run();});auto clean_up_signal_thread = [&startup_thread_ios, &startup_thread]() {startup_thread_ios.stop();startup_thread.join();};try {for( auto plugin : initialized_plugins ) {if( is_quiting() ) break;plugin->startup();}} catch( ... ) {clean_up_signal_thread();shutdown();throw;}

3. exec

void application::exec() {boost::asio::io_service::work work(*io_serv);(void)work;bool more = true;while( more || io_serv->run_one() ) {while( io_serv->poll_one() ) {}// execute the highest priority itemmore = pri_queue.execute_highest();}shutdown(); /// perform synchronous shutdownio_serv.reset(); }

4. shutdown

void application::shutdown() {for(auto ritr = running_plugins.rbegin();ritr != running_plugins.rend(); ++ritr) {(*ritr)->shutdown();}for(auto ritr = running_plugins.rbegin();ritr != running_plugins.rend(); ++ritr) {plugins.erase((*ritr)->name());}running_plugins.clear();initialized_plugins.clear();plugins.clear();quit(); }

5. quit

void application::quit() {my->_is_quiting = true;io_serv->stop(); }

總結

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