Run the some code whenever I upload the project on to the app engine server
There isn't an official way to discover if your application has been modified altought each time you upload your application it gets a unique version number {app version.(some unique number)} but since there isn't a document API on how to get it I wound't take a risk and use it.
What you need todo is to have a script that will upload your application and when the script is done you can call a handler in your application that set a value in the datastore that marks the application as new.
Once you have that, you can look for it in the datastore in your handlers and run the code if you find it.
I've built an appeninge project so, how can I run some piece of code on the appserver only once, i.e  when ever I upload the whole project on to the server.
How should I achieve this task???