How to register a callback for cache objects that expire it's TTL?

Question

My scenario is a list of calling telemetry agents, pinging the server with some status. I need to adjust the control rule when devices drop but I need to know what was the device last contribution.
How do I find all the objects that are about to expire without having to periodically vacuum the cache?
Does TTL expiration fire a notification with the existing object (before removing it) to the callback?
If yes what is the filter operation: Remove?

Answer 1

The documentation makes no description on how the duration parameter interacts with notifications.
I tried a sandbox project.
Created a DataCache object.
Register a callback with filter:
DataCacheOperations
filter = DataCacheOperations.RemoveItem;
The callback sends to the Output screen the notifications
public static void OnCacheNotificationReceived(string myCacheName,
string myRegion,
string myKey,
DataCacheItemVersion itemVersion,
DataCacheOperations OperationId,
DataCacheNotificationDescriptor nd)
//display some of the delegate parameters
Debug.WriteLine("A cache-level notification was triggered!");
Debug.WriteLine(" Cache: " + myCacheName);
Debug.WriteLine(" Region: " + myRegion);
Debug.WriteLine(" Key: " + myKey);
Debug.WriteLine(" Operation: " + OperationId.ToString());
Debug.WriteLine("");
Inserted 1 object using a duration of 30 seconds
_cache.Put(key, obj, TimeSpan.FromSeconds(30));
Then sleep 10 minutes:
Thread.Sleep(TimeSpan.FromSeconds(600));
The callback fired about 5 minutes after the Put method.
Here is my config
<dataCacheClient name="default">
<autoDiscover isEnabled="true" identifier="[my role]"/>
<clientNotification pollInterval="30" maxQueueLength="10000"/>
</dataCacheClient>
What I did wrong?