Worker & Web Role in same application

Question

Hi,

We have a WebRole which deals with request coming in off a WCF service, this validates then puts the messages into an Azure queue in Cloud storage. In the same application we have a WorkerRole which reads the information from the queue and makes a call to our persistence layer which processes the request and returns the result. We were wondering why the worker roles didn't pick up any of our configuration settings and hence was not providing the Trace information we were looking for. We realised that the worker role was likely looking for an app.config and couldn't find it.

Is there a way to point the worker role to the web config, or to be able to load our Enterprise Library settings into the ServiceConfiguration.cscfg file which in either case would mean both could read from a common place?

Many thanks in advance Kindo

Answer 1

As far as I'm aware there is no way for your worker role to get access to the web config of a web role out of the box.

If you move your configuration items to the ServiceConfiguration.csfg file and both the worker and web role are in the same cloud project, the settings will be in the same file. But because the web role and the worker role are different projects within that cloud project, their settings are in different sections of that .csfg file. If you want the settings to be the same for both of them, you will have to duplicate the settings.

Putting your settings in this file gives you the advantage that you can change the settings while the roles are running and have the roles respond however you like e.g. you might want certain settings to restart the roles, for others you may just want to update a static variable. In order to update a web.config or app.config you need to redeploy that role.

You do need to be aware though that the ServiceConfiguration file is not a replacement for a webconfig. If you're using tools that look for their settings in a web or app config, unless they're particularly smart and aware of the Azure environment, they won't go looking for settings in the ServiceConfiguration file.

I know you didn't ask this question, but if you're expecting your worker role to be providing an almost synchronous response to your web role by using a request queue and a response queue, you'll probably find that this won't scale very well. If you want to do synchronous calls to a worker role in Azure you're best off using WCF (this isn't highlighted anywhere in the guides). As you said that all of this is just a WCF service anyway, the answer to your problem may be to just do away with the worker role.

Answer 2

You cannot share web.config's OR .cscfg's across Roles in Azure, as there is no guarantee a role is in the same host, cluster, or even datacenter as another role.

If you are simply trying to share items like connection Strings, app-specific variables, etc., I would simply create your own "config manager" class that would obtain some XML and parse it into a collection of settings. This way, you could store that config on Azure Blob Storage and changes would be as simply as updating that blob and signaling your apps to reload. (very easy using the Service Management API).