Azure - Accessing the same blob from worker role as in web role

Question

I'm pretty new in Azure and I want to create a simple .Net application (in C#) with one web role and one worker role to upload and resize images. I've already made a galery in the web role. It creates a blob then uploads the pictures there, then shows them.

What I want to do now: Sending a message throw a queue to a worker role if any of the pictures are too big then resize them in the worker role. My promblem is that I can't see how to access the same blob which was created in the web role (first I want to access to it in the local development emulator). If I add a new entry in the worker roles properties --> settings page that will give me a completely different blob connection string, doesn't it?

Thanks for any help.

Answer 1

In order to access the same storage account from multiple roles you will need to add the connection string to all roles in the cloud project:

To initialize the client you would write something like this (again, this will be the same on all your roles):

CloudStorageAccount storageAccount = CloudStorageAccount.Parse(
    CloudConfigurationManager.GetSetting("MyStorageAccount"));

Whenever your Web Role sends a message to the queue to notify a Worker Role that the image should be resized, simply include the url or the container name + blob path. With this information your Worker Role will be able to fetch the blob and do the required processing.

I suggest you take a look at the official Windows Azure Training Kit. One of the hands on labs does exactly what you're trying to do here with a Guestbook application (uploading an image on a Web Role, creating a thumbnail in a Worker Role, ...): HOL-IntroToCloudServices Ex2-UsingWorkerRolesAndQueues