Saturday, December 29, 2012

Deploying Applications in the Cloud Using AppScale

In my last two posts I briefly explained how to setup AppScale and get it up and running. Once you have a running AppScale PaaS, you can start deploying webapps in the cloud. You develop webapps for AppScale using Google App Engine (GAE) SDK. AppScale is fully API compatible with GAE and therefore any GAE application can be deployed on AppScale with no code changes. If you do not have any GAE applications to try on AppScale, you may follow one of the official GAE tutorials and develop a sample GAE application using Python, Java or Go. Alternatively you can checkout the AppScale sample-apps repository and try to deploy one of the pre-packaged sample apps. To checkout the sample-apps repository, execute the following command on a shell:
git clone
This will checkout a directory named sample-apps to your local disk. This directory contains 3 subdirectories named python, java and go. As the names suggest, each subdirectory contains a number of sample GAE applications written in the corresponding language. One of the simplest sample applications available for you to try out is the "guestbook" application. The Python version of the application can be found in the sample-apps/python/guestbook directory and the Java version of it can be found in the sample-apps/java/guestbook directory. This application provides a simple web front-end for users to enter a comment and browse comments entered by other users. It uses the GAE datastore API under the hood to store and retrieve comments entered by users. You can use AppScale-Tools to upload the guestbook application to your AppScale cloud.
appscale-upload-app --file samples-apps/python/guestbook --keyname appscale_test
The keyname flag should indicate the keyname you provided when starting the AppScale instance using the appscale-run-instances command. Once you execute the above command you will be prompted to enter the admin e-mail address for your application. Here you can enter the admin e-mail address you used when starting AppScale. Application deployment could take a few minutes. If everything goes smoothly, tools will print the URL through which your webapp can be accessed.
Your app can be reached at the following URL:
Try uploading a few applications using the above command and see how it goes. You can also try developing your own custom apps and deploying them in the cloud. 
AppScale-Tools also allow you to start an AppScale cloud with an application preloaded. To invoke this feature, you simple need to pass the --file option to the appscale-run-instances command.
appscale-run-instances --min 10 --max 10 --infrastructure euca --machine emi-12345678 --keyname appscale_test --group appscale_test --file samples-apps/python/guestbook
To undeploy an application you can use the appscale-remove-app command.
appscale-remove-app --appname guestbook --keyname appscale_test
Finally you can terminate and tear down an AppScale PaaS using the appscale-terminate-instances command.
appscale-terminate-instances --keyname appscale_test
If your AppScale PaaS was running in over an IaaS layer such as EC2, the above command will also take care of terminating the VMs in the cloud.
In my next few posts, I'll explain a little bit about GAE APIs and how to implement cool apps for AppScale using those APIs.

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