Architecture of the Windows Service LMDBService (updated)

Here is the new diagram:



Azure Container Instance

To run my container on ACI, I need a specific image :

FROM microsoft/iis:windowsservercore-ltsc2016

If not, it does not work. The error will be the OS version is not supported.

Envoyé de mon téléphone Windows 10

Windows API vs ISO C++

It’s been a while I am writing softwares for Windows using Win32 API and C runtime. But since some few years, I use ISO C++ and STL features more and more.

My best friends are :

  • std::wstring for string management
  • std::vector for container
  • std::shared_ptr for memory management
  • std::wostringstream for stream

For sure, there is a little overhead compared to C runtime routines but life is easy.

Envoyé de mon téléphone Windows 10

Making a POST call with JSON data using CPPREST C++ SDK

The source code here is the same as the C# version in the previous post. The client makes a simple call like that: 

	std::string value2 = "azertyuiopqsdfghjklmwxcvbn";
	std::string buffer = Base64Helper::base64_encode((const unsigned char*)value2.c_str(), value2.length());
	std::wstring value3(buffer.begin(), buffer.end());
	SetData(key, value3, value3.length(), dbname);


Here is the wrapper code for SetData. It’s included in HttpLMDB dll: 

bool HTTPLMDB_API SetData(std::wstring key, std::wstring valueb64, DWORD dwLen, std::wstring name)
	std::wstring port = Constants::MasterNodePort;
	std::wstring ip = ServerHelper::GetIP();
	std::wstring url = ServerHelper::BuildURL(ip, port);

	std::wstring contentType = _T("Content-Type");
	std::wstring contentTypeV = _T("application/json");
	std::wstring keepAlive = _T("Keep-Alive");
	std::wstring keepAliveV = _T("false");
	std::wstring contentLength = _T("Content-Length");
	std::wostringstream bufLen;
	bufLen << contentType.length() + contentTypeV.length() + keepAlive.length() + keepAliveV.length() + contentLength.length() + 4;
	std::wstring len = bufLen.str().c_str();

	std::wostringstream buf;
	buf << url << '/' << Constants::Request << Constants::VerbSetDataB64
		<< _T("&name=") << name;
	url = buf.str().c_str();	
	std::wostringstream bufjson;
	bufjson << "{" << '"' << "key" << '"' << ":" << '"' << key << '"' << ","
		<< '"' << "value" << '"' << ":" << '"' << valueb64 << '"' << '}';
	std::wstring jsonv = bufjson.str().c_str();
	//wcout << _T("jsonv : ") << jsonv << endl;

	http_client client_lmdb(url);
	http_request request(methods::POST);
	request.headers().add(contentType, contentTypeV);
	request.headers().add(keepAlive, keepAliveV);
	request.headers().add(contentLength, len);

	http_response response;
	response = client_lmdb.request(request).get();

	wcout << response.to_string() << endl;

	return true;


Here is the code. It’s not very difficult.

Handling a long url using POST verb

To be able to store data in my LMDB Service, I need to store data as base64 items. To do that, I need to transmit json data from the client to the server. It can’t be passed on the url. So I use post handling. Here is the C++ handler:

void TheServer::handle_post(http_request message)


             std::wstring request = ServerHelper::FindParameter(message, _T("request"));
              if (request == Constants::VerbSetDataB64)
             else if (request == Constants::VerbGetDataB64)
                    // Does not work yet
       catch (...)
             // an internal problem occured
             g_Logger.WriteLog(_T("handle_post exception..."));


The C++ routine here to analyze is RequestVerbSetData64. Here is the code:

void TheServer::RequestVerbSetData64(http_request message)
       CLMDBWrapper lmdb;
       std::wstring dbNameW = ServerHelper::FindParameter(message, _T("name"));

       std::string dbName(dbNameW.begin(), dbNameW.end());
       std::wstring json;
       web::json::value jsonV = message.extract_json().get();

       Data data = Data::FromJSON(jsonV.as_object());
       TCHAR sz[255];
       _stprintf_s(sz, _T("Data key:%s value:..."), data.key.c_str());

       if (lmdb.Init((LPSTR)dbName.c_str()) == false)
             g_Logger.WriteLog(_T("LMDB Init not done !"));


       LPSTR lpszKey = W2A(data.key.c_str());
       LPSTR lpszValue = W2A(data.value.c_str());
       DWORD dwLen = strlen(lpszValue);

       lmdb.SetData(lpszKey, lpszValue, dwLen);




The source code is simple to write, simple to read. Because it is native code, it is fast and we just need to distribute the dll we use. here, it’s just the C runtime, the C++ runtime and the CPPREST dll. This is the advantage of the native stuff, you don’t need to distribute any framework that size is around 350 MB… It’s lightweight, it’s fast, it’s built on the metal.

Running LMDBService WS NoSQL in Azure Container Instance

Now that LMDBService runs in a docker image, it is possible to run it into Azure Container Instance.

Here are the steps to follow:

  • Build the docker image locally with its dockerfile
    • docker image build –tag mydocker/myserver d:\dev\docker
  • Create a Repository in Azure Repository
  • Connect in docker shell to the repo
    • docker login -u lmdbwsprod -p xxxxxxxxxxxxxxxxxxxxxxxxxx
  • Tag the prod repository
    • docker tag mydocker/myserver
  • Push the docker image to the Azure repository
  • Go to Azure portal and choose Azure Repository
    • Choose prod repository
    • Check tags and choose latest
    • Click Run Instance in […] button
    • Open port 7001
    • Click OK
  • Go to Azure Container Instance
    • choose the container and click Overview
    • Retrieve the IP address

Test the URL :


Architecture of the Windows Service LMDBService

Here is it: