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The AppBase library provides a basic framework for building applications from a set of plugins. AppBase manages the plugin life-cycle and ensures that all plugins are configured, initialized, started, and shutdown in the proper order.

Key Features

  • Dynamically Specify Plugins to Load
  • Automatically Load Dependent Plugins in Order
  • Plugins can specify commandline arguments and configuration file options
  • Program gracefully exits from SIGINT, SIGTERM, and SIGPIPE
  • Minimal Dependencies (Boost 1.60, c++14)

Defining a Plugin

A simple example of a 2-plugin application can be found in the /examples directory. Each plugin has a simple life cycle:

  1. Initialize - parse configuration file options
  2. Startup - start executing, using configuration file options
  3. Shutdown - stop everything and free all resources

All plugins complete the Initialize step before any plugin enters the Startup step. Any dependent plugin specified by APPBASE_PLUGIN_REQUIRES will be Initialized or Started prior to the plugin being Initialized or Started.

Shutdown is called in the reverse order of Startup.

class net_plugin : public appbase::plugin<net_plugin>

     APPBASE_PLUGIN_REQUIRES( (chain_plugin) );

     virtual void set_program_options( options_description& cli, options_description& cfg ) override
              ("listen-endpoint", bpo::value<string>()->default_value( "" ), "The local IP address and port to listen for incoming connections.")
              ("remote-endpoint", bpo::value< vector<string> >()->composing(), "The IP address and port of a remote peer to sync with.")
              ("public-endpoint", bpo::value<string>()->default_value( "" ), "The public IP address and port that should be advertized to peers.")

     void plugin_initialize( const variables_map& options ) { std::cout << "initialize net plugin\n"; }
     void plugin_startup()  { std::cout << "starting net plugin \n"; }
     void plugin_shutdown() { std::cout << "shutdown net plugin \n"; }


int main( int argc, char** argv ) {
   try {
      appbase::app().register_plugin<net_plugin>(); // implict registration of chain_plugin dependency
      if( !appbase::app().initialize( argc, argv ) )
         return -1;
   } catch ( const boost::exception& e ) {
      std::cerr << boost::diagnostic_information(e) << "\n";
   } catch ( const std::exception& e ) {
      std::cerr << e.what() << "\n";
   } catch ( ... ) {
      std::cerr << "unknown exception\n";
   std::cout << "exited cleanly\n";
   return 0;

This example can be used like follows:

./examples/appbase_example --plugin net_plugin
initialize chain plugin
initialize net plugin
starting chain plugin
starting net plugin
shutdown net plugin
shutdown chain plugin
exited cleanly

Boost ASIO

AppBase maintains a singleton application instance which can be accessed via appbase::app(). This application owns a boost::asio::io_service which starts running when appbase::exec() is called. If a plugin needs to perform IO or other asynchronous operations then it should dispatch it via application io_service which is setup to use an execution priority queue.

app().post( appbase::priority::low, lambda )


delay_timer->async_wait( app().get_priority_queue().wrap( priority::low, lambda ) );

Use of get_io_service() directly is not recommended as the priority queue will not be respected.

Because the app calls io_service::run() from within application::exec() and does not spawn any threads all asynchronous operations posted to the io_service should be run in the same thread.

Graceful Exit

To trigger a graceful exit call appbase::app().quit() or send SIGTERM, SIGINT, or SIGPIPE to the process.


  1. c++14 or newer (clang or g++)
  2. Boost 1.60 or newer compiled with C++14 support

To compile boost with c++14 use:

./b2 ...  cxxflags="-std=c++0x -stdlib=libc++" linkflags="-stdlib=libc++" ...


Framework for building applications based upon plugins




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