Can I modify expiration or dependency settings after a data structure is created?

No. In NCache, DataTypeAttributes are immutable once the structure is initialized in the cache. To change these rules, you must remove the existing data structure and recreate it with the updated attribute configurations.

What happens when a Key Dependency is triggered for a distributed collection?

When the referenced primary CacheItem is modified, removed, or expired, NCache automatically invalidates and removes the dependent data structure (e.g., HashSet, List). This ensures seamless distributed consistency without requiring manual synchronization code.

What eviction priority levels are available for NCache collections?

NCache provides five priority levels: High, Above Normal, Normal, Below Normal, and Low. Under memory pressure, items with lower priority are evicted first.

Does NCache support both Absolute and Sliding expiration for data structures?

Yes. You can use Absolute Expiration for a fixed time-to-live from the point of creation, or Sliding Expiration to reset the timeout window every time the data structure is accessed.

Configure Invalidation Attributes for Data Structures in Cache

NCache provides invalidation mechanisms for distributed data structures that control their lifetime and removal behavior in the cache. These mechanisms are configured through the DataTypeAttributes class at the time of data structure creation and apply to all supported distributed data structures. Since these settings define the core behavior of the data structure, they must be specified during initialization and cannot be changed afterward.

The data structures can be invalidated from the cache using:

These attributes are specified during the data structure creation using the DataTypeAttributes class and cannot be modified once a data structure is created in the cache. Moreover, these invalidation attributes can be specified against all data structures.

Note

Key dependencies can be configured between the CacheItem and data structures as well.

Prerequisites

To learn about the standard prerequisites required to work with all NCache client-side features, please refer to the given page on Client-Side API Prerequisites.
For API details, refer to: ICache, DataTypeAttributes, CacheItemPriority, ExpirationType, KeyDependency, IDistributedHashSet, IDataTypeManager, CreateHashSet.

Use Invalidation Attributes with Data Structures

The following code sample creates a set OrderIDSet that is dependent on a Product object in the cache. The OrderIDSet is assigned an expiration value of 15 minutes and its priority is set to high. If the Product is modified in the cache, OrderIDSet is removed from the cache.

// Precondition: Cache is already connected

// Product exists in cache with key "Product:1001"
string productKey = "Product:1001";

// Specify attributes for HashSet
var attributes = new DataTypeAttributes();

// Specify priority for eviction
attributes.Priority = CacheItemPriority.High;

// Specify Absolute expiration of 15 minutes
var expiration = new Expiration(ExpirationType.Absolute, TimeSpan.FromMinutes(15));
attributes.Expiration = expiration;

// Specify key dependency of orderKey on customerKey
var keyDependency = new KeyDependency(productKey);
attributes.Dependency = keyDependency;

// Create HashSet which is dependent on product:1001
// Specify unique cache key for set
string orderKey = "OrderIDSet";
IDistributedHashSet<int> orderIDSet = cache.DataTypeManager.CreateHashSet<int>(orderKey, attributes);

// Check if the orderIDSet exists in cache:
// After 15 minutes or
// If product is modified in cache

// Precondition: Cache is already connected

// Product exists in cache with key "Product:1001"
String productKey = "Product:1001";

// Specify attributes for HashSet
var attributes = new DataStructureAttributes();

// Specify priority for eviction
attributes.setPriority(CacheItemPriority.High);

// Specify Absolute expiration of 15 minutes
var expiration = new Expiration(ExpirationType.Absolute, TimeSpan.FromMinutes(15));
attributes.setExpiration(expiration);

// Specify key dependency of orderKey on customerKey
var keyDependency = new KeyDependency(productKey);
attributes.setDependency(keyDependency);

// Create HashSet which is dependent on product:1001
// Specify unique cache key for set
String orderKey = "OrderIDSet";
WriteThruOptions writeThruOptions = null;

// Create HashSet
DistributedHashSet orderIDSet = InitializeCache.cache.getDataStructuresManager().createHashSet(orderKey, attributes, writeThruOptions, Integer.class);

// Check if the orderIDSet exists in cache:
// After 15 minutes or
// If product is modified in cache

// Precondition: Cache is already connected
// This is an async method

// Product exists in cache with key "Product:1001"
var productKey = "Product:1001";

// Specify attributes for list
var attributes = new ncache.DataStructureAttributes();

// Specify priority for eviction
attributes.setPriority(ncache.CacheItemPriority.High);

// Specify Absolute expiration of 15 minutes
var expiration = new ncache.Expiration(
ncache.ExpirationType.Absolute,
ncache.TimeSpan.fromMinutes(15)
);
attributes.setExpiration(expiration);

// Specify key dependency of orderKey on customerKey
var keyDependency = new ncache.KeyDependency(productKey);
attributes.setDependency(keyDependency);

// Create list which is dependent on product:1001
// Specify unique cache key for list
var orderKey = "OrderIDSet";
var orderIDList = await (
await this.cache.getDataStructuresManager()
).createList(orderKey, Number(), attributes, null);

// Check if the orderIDSet exists in cache:
// After 15 minutes or
// If product is modified in cache

Note

To ensure the operation is fail-safe, it is recommended to handle any potential exceptions within your application, as explained in Handling Failures.

Additional Resources

NCache provides a sample application for configuring invalidation attributes with data structures on GitHub.

Configure Invalidation Attributes for Data Structures in Cache

Note

Prerequisites

Use Invalidation Attributes with Data Structures

Note

Additional Resources

See Also

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