Implement azure colocated caching

Question

Using VS2012 I added the caching feature from the WebRole Properties Caching Tab. Among others, it generated the following XML in web.config:

  <dataCacheClients>   
     <tracing sinkType="DiagnosticSink" traceLevel="Error" />
     <dataCacheClient name="default">
         <autoDiscover isEnabled="true"  identifier="[cluster role name]"/>
         <!-- <localCache isEnabled="true" sync="TimeoutBased" objectCount="100000" ttlValue="300" /> -->
     </dataCacheClient> 
    </dataCacheClients>

Okay, great. I replaced the [cluster role name] with the name of the webrole, say "helloworld.web." Now, when I create the DataCacheFactory or DataCache object:

  _dataCacheFactory = new DataCacheFactory();
    _defaultCache = _dataCacheFactory.GetDefaultCache();

    //Or, just this line
    _defaultCache = new DataCache(@"default");

I get the following error:

Microsoft.ApplicationServer.Caching.DataCacheException was unhandled
  HelpLink=http://go.microsoft.com/fwlink/?LinkId=164049
  HResult=-2146233088
  Message=ErrorCode<ERRCA0021>:SubStatus<ES0001>:Server collection cannot be empty.
  Source=Microsoft.ApplicationServer.Caching.Client
  ErrorCode=21
  SubStatus=-1

Some notes: 
IDE: VS2012,
Framework: 4.0
AzureSDK: June2012
Local dev machine

What am I missing?

Edit

I got it to work!

I was creating the DataCacheFactory in WebRole OnStart method, I moved it over to Application_Start in Global.asax and it seems to be working.

Sandrino explains why this is the case: https://stackoverflow.com/a/11886136/1374935

Answer 1

In your question you talk about adding the XML to the web.config, this works for the web application being hosted in your Web Role (that's why the code works when using it in the Application_Start method).

But you need to know that the code in the WebRole.cs runs in a different process (before even startin the web application). That's why it can't read from your web.config and that's the reason why it seemed there was no server configured.

In order to make that code also work from your WebRole.cs you'll need to add the XML in the config file for the process running that code. Your code runs in the WaIISHost.exe process, so you'll need to create a new configuration file WaIISHost.exe.config, add the XML in this file and change the Copy to Output Directory property for that file to "Copy Always".

Read more about this WaIISHost.exe process here: New Full IIS Capabilities: Differences from Hosted Web Core

Answer 2

I got it to work!

I was creating the DataCacheFactory in WebRole OnStart method, I moved it over to Application_Start in Global.asax and it seems to be working.