OnStart vs Startup Script for batch file? - azure

Question

I have a Ruby on Rails application that needs to find a home in an Azure Worker Role.
I currently automate the deployment of the application with a batch file - a file that takes the apache and ruby installers, runs them, and then drops the RoR app in the appropriate directory. After the batch script finishes, Apache is serving to and from the application via port 80.
I'm new to Azure and trying to figure out how to do this.
From my understanding, I have two options here: OnStart with the installation files in Blob Storage, or a startup script. I'm not sure how to do the latter, but I have located the onStart method within the WorkerRole.vb file in the new Azure project I just created.
My question: Is it recommended to use OnStart to deploy the application (using the batch script)? If so, how would I go about integrating the script into the project? And - how do I get started with storing and referencing the files in blob storage?
I know these are super high-level questions. Any input or suggested reading would be super helpful. I have tried to google / search for relevant resources but haven't been able to find much. Thank you for your time!

Answer 1

When you are inside OnStart() function it is better to do role configuration things i.e. IP binding, etc however if you would want to install runtime, download application zip, configured role specific setting, it is best to use Startup task. Please visit my blog Windows Azure: Startup task or OnStart(), which to choose? to learn more about it.
Now in your case it is best to use Startup task. What you can do it as below:
Create your ROR package a zip and place it at Windows Azure Blob Storage
Create a Cmmmand batch file which will do:
2.1 Download the ZIP
2.2 Unzip to Zip content to a specific location
2.3 Update the status back to AZure Blob Storage (Optional)
In your OnStart() function you just need to configure the ROR
The code will look as below if you have TCP Endpoint name "RORWeb80" set to use port 80:
TcpListener RoRPortListener = new TcpListener(RoleEnvironment.CurrentRoleInstance.InstanceEndpoints["RORWeb80"].IPEndpoint);
RoRPortListener.Start();
I have written a sample app for Tomcat/Java based worker role which does exactly the same. So what you can do it just replace the Tomcat ZIP file with ROR ZIP and reuse the code exactly.

Answer 2

As long as you don't need admin-level access (e.g. modifying registry, installing msi's, etc.) you can do your setup from OnStart(), including launching your script. Just include the startup script with your project (don't forget to set Copy Local to true).
Same goes with startup script: you call your cmd file, which then executes the sequence for you. And if you give it elevated permissions, you can run installers, modify registry settings, install custom perf counters, whatever.
In either case: you can keep your apache zip, ruby installers, etc. in blob storage and, at startup, download them to local storage. This saves you from bundling everything within the deployment, which gives you a few advantages (being able to update ruby / apache without redeploy, reduced package size, etc.).
There's a sample app on codeplex that demonstrates the basics of setting up Tomcat via startup script. For one more example, you can look at the scripts installed via Eclipse Windows Azure plugin for Java. These scripts are quite similar. The key is to have some way of downloading files from blob storage and then unzipping them. the codeplex project I referred to points to a sample app that does simple blob downloading. The Eclipse packaging provides similar functionality in a .vbs app. Here's a snippet of one of my scripts from an Eclipse-based project:
SET SERVER_DIR_NAME=apache-tomcat-7.0.25
SET WAR_NAME=myapp.war
rd "\%ROLENAME%"
mklink /D "\%ROLENAME%" "%ROLEROOT%\approot"
cd /d "\%ROLENAME%"
cscript /NoLogo util\unzip.vbs jre7.zip "%CD%"
cscript /NoLogo util\unzip.vbs tomcat7.zip "%CD%"
copy %WAR_NAME% "%SERVER_DIR_NAME%\webapps\%WAR_NAME%"
cd "%SERVER_DIR_NAME%\bin"
set JAVA_HOME=\%ROLENAME%\jre7
set PATH=%PATH%;%JAVA_HOME%\bin
cmd /c startup.bat
The codeplex project has a similar-looking script.
Don't forget: you'll need to set up an Input Endpoint for your role (part of the role properties).
To get blobs into blob storage, there are both free tools (like Clumsy Leaf CloudXplorer and paid tools (such as Cerebrata's Cloud Storage Studio).
To download blobs to local storage, you can either write a few lines of .net code (from OnStart) or just use the utility pointed to in the codeplex project.