Adding a StructuredLogging stop event

eth/main.cpp

@@ -910,6 +910,7 @@ int main(int argc, char** argv)
 		while (!g_exit)
 			this_thread::sleep_for(chrono::milliseconds(1000));
 
+	structuredLogger.logStopping(clientImplString, dev::Version);
 	auto netData = web3.saveNetwork();
 	if (!netData.empty())
 		writeFile((dbPath.size() ? dbPath : getDataDir()) + "/network.rlp", netData);

libdevcore/StructuredLogger.cpp

@@ -66,6 +66,20 @@ void StructuredLogger::logStarting(string const& _clientImpl, const char* _ethVe
 	}
 }
 
+void StructuredLogger::logStopping(string const& _clientImpl, const char* _ethVersion) const
+{
+	if (m_enabled)
+	{
+		Json::Value event;
+		event["comment"] = "last event before termination of the client";
+		event["client_impl"] = _clientImpl;
+		event["eth_version"] = std::string(_ethVersion);
+		event["ts"] = timePointToString(std::chrono::system_clock::now());
+
+		outputJson(event, "stopping");
+	}
+}
+
 void StructuredLogger::logP2PConnected(string const& _id, bi::tcp::endpoint const& _addr,
 	chrono::system_clock::time_point const& _ts, string const& _remoteVersion, unsigned int _numConnections) const
 {

libdevcore/StructuredLogger.h

@@ -51,6 +51,7 @@ public:
 		m_enabled(_enabled), m_timeFormat(_timeFormat) {}
 
 	void logStarting(std::string const& _clientImpl, const char* _ethVersion) const;
+	void logStopping(std::string const& _clientImpl, const char* _ethVersion) const;
 	void logP2PConnected(std::string const& _id, bi::tcp::endpoint const& _addr,
 		std::chrono::system_clock::time_point const& _ts, std::string const& _remoteVersion, unsigned int _numConnections) const;
 	void logP2PDisconnected(std::string const& _id, bi::tcp::endpoint const& _addr, unsigned int _numConnections) const;