Progress #148: early implementation of solution 2

Needs testing in all the different scenarios, but we no longer fail to
start when resyncing.

libraries/app/application.cpp

@@ -32,6 +32,7 @@
 #include <fc/rpc/websocket_api.hpp>
 
 #include <boost/filesystem/path.hpp>
+#include <boost/signals2.hpp>
 
 #include <iostream>
 
@@ -284,11 +285,17 @@ namespace detail {
       { try {
          ilog("Got block #${n} from network", ("n", blk_msg.block.block_num()));
          try {
-            return _chain_db->push_block( blk_msg.block, _is_block_producer? database::skip_nothing : database::skip_transaction_signatures );
+            return _chain_db->push_block(blk_msg.block, _is_block_producer? database::skip_nothing : database::skip_transaction_signatures);
          } catch( const fc::exception& e ) {
             elog("Error when pushing block:\n${e}", ("e", e.to_detail_string()));
             throw;
          }
+
+         if( !_is_finished_syncing && !sync_mode )
+         {
+            _is_finished_syncing = true;
+            _self->syncing_finished();
+         }
       } FC_CAPTURE_AND_RETHROW( (blk_msg)(sync_mode) ) }
 
       virtual bool handle_transaction(const graphene::net::trx_message& trx_msg, bool sync_mode) override
@@ -408,7 +415,7 @@ namespace detail {
        * @param item_count the number of items known to the node that haven't been sent to handle_item() yet.
        *                   After `item_count` more calls to handle_item(), the node will be in sync
        */
-      virtual void     sync_status(uint32_t item_type, uint32_t item_count) override
+      virtual void sync_status(uint32_t item_type, uint32_t item_count) override
       {
          // any status reports to GUI go here
       }
@@ -416,7 +423,7 @@ namespace detail {
       /**
        * Call any time the number of connected peers changes.
        */
-      virtual void     connection_count_changed(uint32_t c) override
+      virtual void connection_count_changed(uint32_t c) override
       {
         // any status reports to GUI go here
       }
@@ -470,6 +477,8 @@ namespace detail {
       std::shared_ptr<fc::http::websocket_tls_server>  _websocket_tls_server;
 
       std::map<string, std::shared_ptr<abstract_plugin>> _plugins;
+
+      bool _is_finished_syncing = false;
    };
 
 }
@@ -579,6 +588,11 @@ optional< api_access_info > application::get_api_access_info( const string& user
    return my->get_api_access_info( username );
 }
 
+bool application::is_finished_syncing() const
+{
+   return my->_is_finished_syncing;
+}
+
 void graphene::app::application::add_plugin(const string& name, std::shared_ptr<graphene::app::abstract_plugin> p)
 {
    my->_plugins[name] = p;

libraries/app/include/graphene/app/application.hpp

@@ -77,6 +77,10 @@ namespace graphene { namespace app {
          void set_block_production(bool producing_blocks);
          fc::optional< api_access_info > get_api_access_info( const string& username )const;
 
+         bool is_finished_syncing()const;
+         /// Emitted when syncing finishes (is_finished_syncing will return true)
+         boost::signals2::signal<void()> syncing_finished;
+
       private:
          void add_plugin( const string& name, std::shared_ptr<abstract_plugin> p );
          std::shared_ptr<detail::application_impl> my;

libraries/plugins/witness/witness.cpp

@@ -86,12 +86,28 @@ void witness_plugin::plugin_initialize(const boost::program_options::variables_m
 
 void witness_plugin::plugin_startup()
 { try {
-      std::set<chain::witness_id_type> bad_wits;
-      //Start NTP time client
-      graphene::time::now();
-      for( auto wit : _witnesses )
+   chain::database& d = database();
+   std::set<chain::witness_id_type> bad_wits;
+   //Start NTP time client
+   graphene::time::now();
+   for( auto wit : _witnesses )
    {
-      auto signing_key = wit(database()).signing_key;
+      if( d.find(wit) == nullptr )
+      {
+         if( app().is_finished_syncing() )
+         {
+            elog("ERROR: Unable to find witness ${w}, even though syncing has finished. This witness will be ignored.",
+                 ("w", wit));
+            continue;
+         } else {
+            wlog("WARNING: Unable to find witness ${w}. Postponing initialization until syncing finishes.",
+                 ("w", wit));
+            app().syncing_finished.connect([this]{plugin_startup();});
+            return;
+         }
+      }
+
+      auto signing_key = wit(d).signing_key;
       if( !_private_keys.count(signing_key) )
       {
          // Check if it's a duplicate key of one I do have
@@ -119,7 +135,7 @@ void witness_plugin::plugin_startup()
    {
       ilog("Launching block production for ${n} witnesses.", ("n", _witnesses.size()));
       app().set_block_production(true);
-      schedule_next_production(database().get_global_properties().parameters);
+      schedule_next_production(d.get_global_properties().parameters);
    } else
       elog("No witnesses configured! Please add witness IDs and private keys to configuration.");
 } FC_CAPTURE_AND_RETHROW() }