A Windows Service with C++ NoSQL in Azure Container Instance

The case study is a NoSQL WS that offers Read/Write possibilities for multiple databases using a REST API.

The NoSQL technology is OpenLDAP-LMDB library. It was ported from Linux to Windows and exported as a Windows DLL.

A Windows Service exposes a WS hosted by CPP REST SDK as a stand alone Web Server on a dedicated url/port. In my case, port is 7001, url is /MyServer/LMDB/.

The docker container run in Azure Container Instance using a Window Server 2016 1609 image from microsoft/iis:windowsservercore-ltsc2016.

DockerFile is:

The project is a Windows Service x64 (LMDBService.exe) who loads multiple dll :

• cpprest141d_2_10.dll
• LMDBWindowsDllD64.dll
• LMDBWrapperD64.dll
• MySharedStuffD64.dll
• Msvcp140d.dll
• Vcruntime140d.dll
• Ucrtbased.dll

The Windows service consume 2 MB of memory and PCU is always 0%. It’s the advantage of C++.

The Windows service needs to be run as administrator because cpp rest sdk require admin privileges to create the url on a port. Else ACCESS_DENIED error.

The docker image is built localy (W10) and uploaded in Azure Container Registry.

• docker image build –tag myserver6 d:devdocker
• docker login lmdbreg.azurecr.io -u lmdbreg -p XXXXXXXXXXXXXXXXXXXXXXXXXXXX
• docker tag myserver6 lmdbreg.azurecr.io/prod6
• docker push lmdbreg.azurecr.io/prod6

Azure container url : http://137.117.141.0:7001/MyServer/LMDB/request?ping

The container is up & running.

There are multiple verbs in HTTP :

• GET : get-data, set-data, ping
• POST : get-data-b64, set-data-b64

Anything else route to about.

The container use IIS to see the private log file (LMDB.txt).

Logs : http://137.117.141.0/Logs/lmdb.txt

The container use the port 7001 and writes/reads data from c:temp and c:templogs

http://137.117.141.0:7001/MyServer/LMDB/?request=ping

http://137.117.141.0:7001/MyServer/LMDB/?request=about

Sample GET requests:

INFO – 7:05:41 PM – http://137.117.141.0:7001/MyServer/LMDB/?request=set-data&key=Key_v0&value=Value_v0&name=cache_NET

INFO – 7:05:41 PM – {"key":"Key_v0","value":"Value_v0"}

INFO – 7:05:41 PM – http://137.117.141.0:7001/MyServer/LMDB/?request=get-data&key=Key_v0&name=cache_NET

INFO – 7:05:42 PM – {"key":"Key_v0","value":"Value_v0"}

For POST requests, you need code C# or JS…

Example :

private static void StoreFile(string url, string path)

{

string cache = "cache_NET";

string base_url = String.Format("http://{0}:7001/MyServer/LMDB/?request=set-data-b64&name={1}", url, cache);

var enc = System.Text.Encoding.UTF8;

string key = path;

string value = String.Empty;

byte[] buffer = File.ReadAllBytes(path);

string buffer2 = enc.GetString(buffer);

value = Base64Helper.Base64Encode(buffer2);

MakePostBuffer(base_url, value);

}

private static void MakePostBuffer(string url, string valueb64)

{

HttpWebRequest r = (HttpWebRequest)WebRequest.Create(url);

string c = """;

string a1 = "{";

string a2 = "}";

string key = String.Format("key_{0}", DateTime.Now.Ticks);

string postData = String.Format("{1}{0}key{0}:{0}{4}{0}, {0}value{0}:{0}{3}{0}{2}", c, a1, a2, valueb64, key); // url;

//Logger.LogInfo(postData);

var data = Encoding.ASCII.GetBytes(postData);

r.Method = "POST";

r.ContentType = "application/json;";

r.ContentLength = data.Length;

r.KeepAlive = false;

using (var stream = r.GetRequestStream())

{

stream.Write(data, 0, data.Length);

}

string str = String.Format("Sending {0} bytes on {1}", data.Length, url);

Logger.LogInfo(str);

WebResponse wr = r.GetResponse();

//Logger.LogInfo(wr.ContentType);

Stream s = wr.GetResponseStream();

Encoding encode = System.Text.Encoding.GetEncoding("utf-8");

StreamReader reader = new StreamReader(s, encode);

string buffer = reader.ReadToEnd();

Logger.LogInfo(buffer);

reader.Close();

wr.Close();

}

Christophe Pichaud