Absolute Data Expiration in Cache
NCache allows you to configure absolute expiration with your cache items. This will expire the items at the exact date and time specified by the client. Absolute expiration can be specified on items that are required for a limited time in the cache. For example, a company announces flash sale for 24 hours on certain products. These items can then be cached with an absolute expiration of 24 hours so they are expired from the cache as soon as the sale ends.
Moreover, this DateTime value is converted to UTC time to cater the case where the cache server and client are in different time zones. So the items will be expired at the exact time which has been specified by the user.
Prerequisites
Add/Update Item with Absolute Expiration
You add/update the cache items to set expiration, using the Insert method.
CacheItem is a custom class provided by NCache which can be used to add data to the cache and also lets you set additional metadata associated with an object of this class. This metadata defines the properties of the item like expiration, dependencies and more.
The following example sets the value of the Expiration property to Absolute Expiration of 5 minutes for a CacheItem and adds it to the cache if the key does not exist - and updates the item if it exists. This CacheItem will then be removed from the cache after 5 minutes.
Tip
You can monitor/verify expiration through:
- "Cache Count" Counter in NCache Web Monitor or PerfMon Counters
- Using
cache.Contains() after expiration interval has elapsed
- Using
cache.Count before and after specifying expiration.
try
{
// Pre-condition: Cache is already connected
// Get product from database against given product ID
Product product = FetchProductFromDB(1001);
// Generate a unique cache key for this product
string key = $"Product:{product.ProductID}";
// Create a new CacheItem for this product
var cacheItem = new CacheItem(product);
// Set Expiration TimeSpan
var expiration = new Expiration(ExpirationType.Absolute, TimeSpan.FromMinutes(5));
cacheItem.Expiration = expiration;
// Add/Update item with expiration
cache.Insert(key, cacheItem);
}
catch (OperationFailedException ex)
{
// Exception can occur due to:
// Connection Failures
// Operation Timeout
// Operation performed during state transfer
}
catch (Exception ex)
{
// Any generic exception like ArgumentNullException or ArgumentException
}
try
{
// Pre-condition: Cache is already connected
// Get product from database against given product ID
Product product = fetchProductFromDB(1001);
// Generate a unique cache key for this product
String key = "Product:" + product.getProductID();
// Create a new CacheItem for this product
CacheItem cacheItem = new CacheItem(product);
// Set Expiration type and TimeSpan
Expiration expiration = new Expiration(ExpirationType.Absolute, TimeSpan.FromMinutes(5));
cacheItem.setExpiration(expiration);
// Add/Update item in cache with expiration
cache.insert(key, cacheItem);
}
catch (OperationFailedException ex)
{
// Exception can occur due to:
// Connection Failures
// Operation Timeout
// Operation performed during state transfer
}
catch (Exception ex)
{
// Any generic exception like IllegalArgumentException or NullPointerException
}
try {
// Pre-condition: Cache is already connected
// Get product from database against given product ID
val product = fetchProductFromDB(1001)
// Generate a unique cache key for this product
val key = "Product:" + product.getProductId
// Create a new CacheItem for this product
val cacheItem = new CacheItem(product)
// Set DataExpiration type and TimeSpan
val expiration = Expiration(ExpirationType.Absolute, TimeSpan.FromMinutes(5))
cacheItem.setExpiration(expiration)
// Add/Update item in cache with expiration
cache.insert(key, cacheItem)
}
catch {
case exception: Exception => {
// Handle any errors
}
}
// This is an async method
try
{
// Pre-condition: Cache is already connected
// Get product from database against given product ID
var product = this.fetchProductFromDB(1001);
// Generate a unique cache key for this product
var key = "Product:" + product.getProductID();
// Create a new CacheItem for this product
// You also need to specify the FQN (Fully Qualified Name) of the class
var cacheItem = new ncache.CacheItem(product,"FQN.Product");
// Set Expiration type and TimeSpan
var expiration = new ncache.Expiration(ncache.ExpirationType.Absolute, ncache.TimeSpan.FromMinutes(5));
cacheItem.setExpiration(expiration);
// Add/Update item in cache with expiration
await this.cache.insert(key, cacheItem);
}
catch (error)
{
// Handle errors
}
try:
# Pre-condition: Cache is already connected
# Get product from database
product = fetch_product_from_db()
# Generate a unique cache key for this product
key = "Product:" + product.get_product_id()
# Create a new CacheItem for this product
cache_item = ncache.CacheItem(product)
# Set Expiration type and TimeSpan
expiration = ncache.Expiration(ncache.ExpirationType.ABSOLUTE, ncache.TimeSpan.from_minutes(5))
cache_item.set_expiration(expiration)
# Add / Update item in cache with expiration
cache.insert(key, cache_item)
except Exception as exp:
# Handle errors
Note
This feature is only available in NCache Enterprise Edition.
You can specify absolute expiration in the API using the DefaultAbsolute and DefaultAbsoluteLonger values configured in NCache Web Manager or config.ncconf. This provides flexibility of changing the value externally if needed, without changing the code.
The following code associates configured default expiration (DefaultAbsolute in this case) with an item and adds it to the cache if the key does not exist in cache, and updates the item with expiration if the key exists. Once the configured time has elapsed, the item is expired.
Important
To enable default expiration, it is mandatory that you enable it through NCache Web Manager or config.ncconf. If you pass the API for default expiration and it is not configured through NCache Web Manager or config.ncconf, it will not work.
Tip
You can monitor/verify expiration through:
- "Cache Count" Counter in NCache Web Monitor or PerfMon Counters
- Using
cache.Contains() after expiration interval has elapsed
- Using
cache.Count before and after specifying expiration
try
{
// Pre-condition: Cache is already connected
// Get product from database against given product ID
Product product = FetchProductFromDB(1001);
// Generate a unique cache key for this product
string key = $"Product:{product.ProductID}";
// Create a cacheItem instance for product
var cacheItem = new CacheItem(product);
// Set Expiration type
var expiration = new Expiration(ExpirationType.DefaultAbsolute);
cacheItem.Expiration = expiration;
// Add/Update item into the cache with default expiration
CacheItemVersion version = cache.Insert(key,cacheItem);
}
catch (OperationFailedException ex)
{
// Exception can occur due to:
// Connection Failures
// Operation Timeout
// Operation performed during state transfer
}
catch (Exception ex)
{
// Any generic exception like ArgumentNullException or ArgumentException
}
try
{
// Pre-condition: Cache is already connected
// Get product from database against given product ID
Product product = fetchProductFromDB(1001);
// Generate a unique cache key for this product
String key = "Product:" + product.getProductID();
// Create a cacheItem instance for product
CacheItem cacheItem = new CacheItem(product);
// Set Expiration type
Expiration expiration = new Expiration(ExpirationType.DefaultAbsolute);
cacheItem.setExpiration(expiration);
//Add/Update item into the cache with default expiration
CacheItemVersion version = cache.insert(key, cacheItem);
}
catch (OperationFailedException ex)
{
// Exception can occur due to:
// Connection Failures
// Operation Timeout
// Operation performed during state transfer
}
catch (Exception ex)
{
// Any generic exception like IllegalArgumentException or NullPointerException
}
try {
// Pre-condition: Cache is already connected
// Get product from database against given product ID
val product = fetchProductFromDB(1001)
// Generate a unique cache key for this product
val key = "Product:" + product.getProductId
// Create a cacheItem instance for product
val cacheItem = new CacheItem(product)
// Set Expiration type
val expiration = Expiration(ExpirationType.DefaultAbsolute)
cacheItem.setExpiration(expiration)
//Add/Update item into the cache with default expiration
val version = cache.insert(key, cacheItem)
}
catch {
case exception: Exception => {
// Handle any errors
}
}
// This is an async method
try
{
// Pre-condition: Cache is already connected
// Get product from database against given product ID
var product = this.fetchProductFromDB(1001);
// Generate a unique cache key for this product
var key = "Product:" + product.getProductID();
// Create a cacheItem instance for product
// You also need to specify the FQN(Fully Qualified Name) of the class
var cacheItem = new ncache.CacheItem(product,"FQN.Product");
// Set Expiration TimeSpan
var expiration = new ncache.Expiration(ncache.ExpirationType.DefaultAbsolute);
cacheItem.setExpiration(expiration);
var version = await this.cache.insert(key, cacheItem);
}
catch (error)
{
// Handle errors
}
try:
# Pre-condition: Cache is already connected
# Get product from database
product = fetch_product_from_db()
# Generate a unique cache key for this product
key = "Product:" + product.get_product_id()
# Create a new CacheItem for this product
cache_item = ncache.CacheItem(product)
# Set Expiration type and TimeSpan
expiration = ncache.Expiration(ncache.ExpirationType.DEFAULT_ABSOLUTE)
cache_item.set_expiration(expiration)
# Add / Update item in cache with expiration
version = cache.insert(key, cache_item)
except Exception as exp:
# Handle errors
Set Absolute Expiration to Existing Item
NCache also provides the flexibility to set Absolute expiration to an existing cache item without having to reinsert it to cache. This is done through CacheItemAttribute class, which has the AbsoluteExpiration property to be set against the cache item. This sets the exact date and time at which the item should be invalidated from the cache.
The attribute is then set against the existing key of the item, using the UpdateAttributes method of ICache.
The following example sets the absolute expiration for an item that already exists within the cache with no expiration set. This requires no need of re-adding or re-inserting the item into the cache.
Tip
You can monitor/verify expiration through:
- "Cache Count" Counter in NCache Web Monitor or PerfMon Counters
- Using
cache.Contains() after expiration interval has elapsed
- Using
cache.Count before and after specifying expiration
try
{
// Pre-condition: Cache is already connected
// Pre-condition: Item already exists in cache
string key = "Product:1001";
// Create a CacheItemAttribute for absolute expiration
// and set its value to 5 seconds
var attr = new CacheItemAttributes();
attr.AbsoluteExpiration = DateTime.Now.AddSeconds(5);
// Set Absolute Expiration of 5 seconds against existing key
cache.UpdateAttributes(key, attr);
}
catch (OperationFailedException ex)
{
// Exception can occur due to:
// Connection Failures
// Operation Timeout
// Operation performed during state transfer
}
catch (Exception ex)
{
// Any generic exception like ArgumentNullException or ArgumentException
}
try
{
// Pre-condition: Cache is already connected
// Pre-condition: Item already exists in cache
String key = "Product:1001";
// Create a CacheItemAttribute for absolute expiration
// and set its value to 5 seconds
Calendar calendar = Calendar.getInstance();
calendar.add(Calendar.SECOND, 5);
CacheItemAttributes attr = new CacheItemAttributes();
attr.setAbsoluteExpiration(calendar.getTime());
// Set Absolute Expiration of 5 seconds against existing key
cache.updateAttributes(key, attr);
}
catch (OperationFailedException ex)
{
// Exception can occur due to:
// Connection Failures
// Operation Timeout
// Operation performed during state transfer
}
catch (Exception ex)
{
// Any generic exception like IllegalArgumentException or NullPointerException
}
try {
// Pre-condition: Cache is already connected
// Pre-condition: Item already exists in cache
val key = "Product:1001"
// Create a CacheItemAttribute for absolute expiration
// and set its value to 5 seconds
val calendar = Calendar.getInstance
calendar.add(Calendar.SECOND, 5)
val attr = CacheItemAttributes()
attr.setAbsoluteExpiration(calendar.getTime)
// Set Absolute Expiration of 5 seconds against existing key
cache.updateAttributes(key, attr)
}
catch {
case exception: Exception => {
// Handle any errors
}
}
// This is an async method
try
{
// Pre-condition: Cache is already connected
// Pre-condition: Item already exists in cache
var key = "Product:1001";
// Create a CacheItemAttribute for absolute expiration
// and set its value to 5 seconds
var time = new Date().getSeconds()+5;
var attr = new ncache.CacheItemAttributes();
attr.setAbsoluteExpiration(time);
// Set Absolute Expiration of 5 seconds against existing key
await this.cache.updateAttributes(key, attr);
}
catch (error)
{
// Handle errors
}
try:
# Pre-condition: Cache is already connected
# Pre - condition: Item already exists in cache
key = "Product:1001"
# Create a CacheItemAttribute for absolute expiration and set its value to 5 seconds
time = datetime.now() + timedelta(seconds=5)
attr = ncache.CacheItemAttributes()
attr.set_absolute_expiration(time)
# Set Absolute Expiration of 5 seconds against existing key
cache.update_attributes(key, attr)
except Exception as exp:
# Handle errors
Additional Resources
NCache provides a sample application for Absolute Expiration on
GitHub.
See Also
Sliding Data Expiration in Cache
Cache Data Expiration
Named Tags
Data Dependency for Relationship in Cache