CacheOutput Attribute Ignoring Azure-hosted Redis Cache

Question

I have just implemented output caching of my Asp.Net Web API Controllers using StrathWeb's library connecting to the StackExchange.Redis library connecting through to an Azure-hosted Redis Cache.

I have written a custom class that implements the StrathWeb IApiOutputCache interface and calls the equivalent StackExchange methods. This is registered as the cache output provder in Global.asax.cs.

Here's an example of usage:

public class MyApiController : ApiController
{
  private const int FIFTEEN_MINUTES_IN_SECONDS = 900;

  [CacheOutput(ClientTimeSpan = FIFTEEN_MINUTES_IN_SECONDS, ServerTimeSpan = FIFTEEN_MINUTES_IN_SECONDS)]
  async public Task<Data> GetAsync(int param1, string param2)
  {
    return await GetExpensiveData();
  }

  [Serializable]
  public class Data
  {
    // Members omitted for brevity
  }
}

When a call is made to the api endpoint I can see that the framework correctly calls all the required methods on my IApiOutputCache class: Contains, Set and Get. However, even when a cached copy is found and returned, the GetExpensiveData() method is always run and the 'fresh' data returned.

No errors are thrown. The cache seems to be working. Yet, my expensive code is always called.

Thanks for your help :).

Can you share your IApiOutputCache Redis implementation?

tuler
– tuler

2015-02-01 15:50:14 +00:00
Commented Feb 1, 2015 at 15:50 — tuler
– tuler, Commented Feb 1, 2015 at 15:50

Chris Arnold · Accepted Answer · 2014-10-28 12:56:06Z

2

Problem solved. I was incorrectly calling into Redis from my IApiOutputCache class.

Before...

public class AzureRedisApiOutputCache : IApiOutputCache
{
  public object Get(string key)
  {
    return AzureRedisCache.Instance.GetDatabase().StringGet(key);
  }
}

After...

public class AzureRedisApiOutputCache : IApiOutputCache
{
  public object Get(string key)
  {
    // Call the extension method that also performs deserialization...
    return AzureRedisCache.Instance.GetDatabase().Get(key);
  }
}

public static class RedisDatabaseExtensions
{
    public static object Get(this IDatabase cache, string key)
    {
        return Deserialize<object>(cache.StringGet(key));
    }
}

This confused me for some time as the CacheOutput framework never reported an error. It just silently failed and fell back to the controller method.

answered Oct 28, 2014 at 12:56

Chris Arnold

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