...

| Property | Type | Default | Description | | ----------------- | :------: | :-----: | ----------- | | initialCapacity | Integer | 16 | The minimum size of the cache | | maximumSize | Long | | The maximum size of the cache. Can not be combined with a weigher | | maximumWeight | Long | | The maximum weight to be allowed for an element in the cache (see Weigher section) | | expireAfterWrite | Duration | | The time to wait to expire an element after its creation | | expireAfterAccess | Duration | 5m | The time to wait to expire an element after the last time it was accessed | | recordStats | boolean | true | To record statistics about hit rates and evictions (see Cache Statistics section) | | testMode | boolean | false | To execute all cache operations in a single thread |

Each cache must have a unique name, which will be automatically normalized to kebab-case (i.e. myEntity becomes my-entity)

A default configuration for a cache can be defined as a bean:

@Factory
@Requires(missingProperty = LocalCacheProperties.PREFIX + "." + MyEntityCacheConfig.CACHE_NAME)
public class MyEntityCacheConfig {
  public static final String CACHE_NAME = "my-entity";


  @Bean
  @Named(CACHE_NAME)
  LocalCacheProperties cacheProperties(ApplicationConfiguration applicationConfiguration) {
    return LocalCacheProperties.builder()
            .cacheName(CACHE_NAME)
            .applicationConfiguration(applicationConfiguration)
            .build();
  }
}

Weigher

A weigher determines if an element becomes too heavy to be in the cache. If for a cache's maximumWeight there is not a corresponding named weigher, any other weigher will be selected. If there is no registered weigher, a default weigher where every element has a weight of 1 will be used:

import com.github.benmanes.caffeine.cache.*;

@Singleton
@Named(MyEntityCacheConfig.CACHE_NAME)
public class MyEntityCacheWeigher implements Weigher<UUID, MyEntity> {
  @Override
  public @NonNegative int weigh(@NonNull UUID key, @NonNull MyEntity value) {
    return 0;
  }
}

Removal Listener

A listener that triggers every time an element is evicted:

import com.github.benmanes.caffeine.cache.*;

@Singleton
@Named(MyEntityCacheConfig.CACHE_NAME)
public class MyEntityCacheRemovalListener implements RemovalListener<UUID, MyEntity> {
  @Override
  public void onRemoval(@Nullable UUID key, @Nullable MyEntity value, @NonNull RemovalCause cause) {
    // Do something with the event
  }
}

Annotation-based caching

Any class (POJOs, Connections, Factories...) can be stored in the cache. For example, instances of the following entity type:

@Data
public class MyEntity implements CoreEntity<UUID> {
  private UUID id;
  private String name;
  ...
}

can be cached in any managed bean with the use of io.micronaut.cache.annotation annotations:

• @Cacheable
• @CachePut
• @CacheInvalidate

@Singleton
@CacheConfig(MyEntityCacheConfig.CACHE_NAME)
public class MyEntityService {

  @Inject
  protected MyEntityRepository myEntityRepository;


  @Cacheable(keyGenerator = CoreEntityKeyGenerator.class)
  public List<MyEntity> getAll() {
    return myEntityRepository.getAll();
  }


  @Cacheable
  public MyEntity getOne(UUID id) {
    return myEntityRepository.getOne(id);
  }


  @CachePut(keyGenerator = CoreEntityKeyGenerator.class)
  public void store(MyEntity myEntity) {
    myEntityRepository.store(myEntity);
  }


  @CacheInvalidate
  public MyEntity delete(UUID id) {
    return myEntityRepository.delete(id);
  }
}

The key for the cacheable object must implement equals() and hashCode()

Note that for the getAll() and store(MyEntity) methods, a custom key generator needs to be specified. This way the cache will calculate the appropriate key for each entity. If no generator is defined, the DefaultCacheKeyGenerator is used.

The CoreEntityKeyGenerator can be used with any entity that implements CoreEntity<T>

Multiple caches can be configured in the same @CacheConfig, in which case, the name of the used cache must be specified. Likewise, the key for the cached value can be a composite of multiple objects (internally wrapped as a ParametersKey and generated by a DefaultCacheKeyGenerator):

@Singleton
@CacheConfig({ "cacheA", "cacheB" })
public class MyMultiCacheService {

  @Cacheable("cacheA")
  public MyEntity getOneA(UUID id) {
    ...
  }


  @Cacheable("cacheB")
  public MyEntity getOneB(UUID id, UUID parentId) {
    ...
  }
}

Cache Statistics

If the cache statistics are enabled, they will be published as part of the application metrics:

• cache.eviction.weight - the sum of weights of evicted entries
• cache.evictions - the count of cache evictions
• cache.size - the estimated number of entries in the cache
• cache.gets - the number of times a cache-annotated method has returned an item (regardless if it was cached or not). This metric can be refined with the use of tags:
  • result:hit - the number of times cache lookup methods have returned a cached value
  • result:miss - the number of times cache lookup methods have returned an uncached value

If the application has multiple caches, the metrics can be filtered with the cache:my-entity tag

Collections

Flushable Collection

A data structure that asynchronously flushes its content any time a preconfigured criteria is met. It is backed up by an ArrayList<T> and it is guaranteed to be thread-safe.

Configuration

Basic Properties

| Property | Type | Default | Description | | ------------ | :------: | :-----: | ----------- | | maxCount | Integer | | The maximum number of elements before flushing. Triggers a Count flush | | maxDataSize | Long | | The maximum size of the collection elements before flushing. Triggers a Data Size flush | | flushAfter | Duration | | The duration before flushing. Triggers a Scheduled flush | | threads | Integer | 5 | The number of threads used to execute the flush event | | flushTimeout | Duration | 10m | The timeout for the flush event |

Properties Template

For a collection of type my-collection, a set of default properties can be defined as a bean or in the application.yml:

collections:
  flushable:
    myCollection:
      maxCount: 10
      maxDataSize: 1mb
      flushAfter: 5m
      threads: 10
      flushTimeout: 10m

The same configuration can be defined as:

@Factory
@Requires(missingProperty = FlushableCollectionProperties.PREFIX + "." + MyFlushableCollectionConfig.TYPE)
public class MyFlushableCollectionConfig {
  public static final String TYPE = "my-collection";


  @Bean
  @Named(TYPE)
  FlushableCollectionProperties collectionProperties() {
    return FlushableCollectionProperties.builder()
            .type(TYPE)
            .maxCount(10)
            .maxDataSize(DataSize.ofMegabytes(1).asBytes())
            .flushAfter(Duration.ofMinutes(5))
            .threads(10)
            .flushTimeout(Duration.ofMinutes(10))
            .build();
  }
}

Each collection definition must have a unique name, which will be automatically normalized to kebab-case (i.e. myCollection becomes my-collection)

Action Handlers

Flush Handler

Consumer to be called when the flush event is triggered. For instance, a flush handler for a collection of integer elements can be defined as:

public class MyCollectionFlushHandler implements Consumer<FlushableCollection.Batch<Integer>> {
  @Override
  public void accept(FlushableCollection.Batch<Integer> batch) {
    // Do something with the batch
  }
}

By default, does nothing: builder.flushHandler(batch -> {})

Weigher

Function to determine the size of an element. Required to trigger a Data Size flush. For instance, a collection of integer elements can define its weigher as:

public class MyCollectionWeigher implements Function<Integer, Long> {
  @Override
  public Long apply(Integer element) {
    return element.toString().length();
  }
}

By default, the weight is calculated after converting the element to String and counting its number of bytes using UTF-8 encoding.

Success Handler

Consumer to be executed if the flush handler was successfully executed. For instance, a success handler for a collection of integer elements can be defined as:

public class MyCollectionSuccessHandler implements Consumer<FlushableCollection.Batch<Integer>> {
  @Override
  public void accept(FlushableCollection.Batch<Integer> batch) {
    // Do something with the successful batch
  }
}

By default, logs a debug message with the details of the processed batch: builder.successHandler(batch -> log.debug(...))

Failure Handler

BiConsumer to be executed if the flush handler failed. For instance, a failure handler for a collection of integer elements can be defined as:

public class MyCollectionFailureHandler implements Consumer<FlushableCollection.Batch<Integer>, Throwable> {
  @Override
  public void accept(FlushableCollection.Batch<Integer> batch, Throwable ex) {
    // Do something with the failed batch
  }
}

By default, logs an error message with the details of the batch and its exception: builder.failureHandler((batch, ex) -> log.error(...)). If the flush event causes a timeout, the input Throwable will be of type java.util.concurrent.TimeoutException.

Usage

The collection must be created through the FlushableCollectionFactory bean, by providing the expected type. If the application context finds a FlushableCollectionProperties with the same name, it will be used as template for the new collection. Otherwise, a new properties set with default values will be created. Note that any pre-defined property can be overridden during the build phase.

@Inject
protected FlushableCollectionFactory flushableCollectionFactory;

        void submit() {
        try (var collection = flushableCollectionFactory.<Integer>builder("my-collection")
        .flushHandler(new MyCollectionFlushHandler())
        .weigher(new MyCollectionWeigher())
        .successHandler(new MyCollectionSuccessHandler())
        .failureHandler(new MyCollectionFailureHandler())
        .build()) {

        for (int i = 0; i < 10; i++) {
        collection.add(i);
        }
        }
        }

Flush Events

• COUNT - Triggers if the collection contains more elements than the value defined in the maxCount property. If undefined, it will never be triggered.
• DATA_SIZE - Triggers if the size of the elements in the collection is greater than the value defined in the maxDataSize property. If undefined, it will never be triggered.
• SCHEDULED - Triggers based on the schedule defined with the flushAfter property. If undefined, it will never be triggered.
• MANUAL - Triggers whenever the collection.flush() method is called.
• CLOSE - Triggers whenever the collection is closed by either using a try with resources, or by calling the collection.close() method.

Flush Metrics

Each collection will publish metrics about the duration of each flush event, its size, and the count of success/failures (see Metrics section).

This can be refined with the use of custom tags during the creation of the collection:

try (var collection = flushableCollectionFactory.<Integer>builder("my-collection")
        .tag("key", "value")
        .build()) {
        // Do something with the collection
        }

The metrics will then be available in:

• GET /metrics/pdp.collections.flushable.[type] - The count of successful and failed flush events.
• GET /metrics/pdp.collections.flushable.[type].duration - The duration for the flush handler.
• GET /metrics/pdp.collections.flushable.[type].size - The size of the flushed elements.

DSL

The PDP DSL is an abstract definition for a common language to be used in any PDP product. Its intention is to have a standardized way to express configurations that might be interpreted in a different way according to the needs of the product itself.

Filters

A filter is a criteria to be applied to a given object. In order to use it, the FilterAdapter interface needs to be implemented. The core supports the following concrete adapters:

• MapFilterAdapter - Converts the filter into a predicate used to evaluate Map<String, Object> structures. The expected field name is the key of the map.
• JsonPathFilterAdapter - Converts the filter into a predicate used to evaluate DocumentContext structures. The expected field name is a JSON Path to be found in the JSON document.
• JsonPointerFilterAdapter - Converts the filter into a predicate used to evaluate ObjectNode structures. The expected field name is a JSON Pointer to be found in the JSON document.

All filters have an optional source field that could be used by the concrete implementation to select among multiple data structures

"Equals" Filter

The value of the field must be exactly as the one provided.

var filter = EqualsFilter.builder().field("field").value("value").build();

{
  "equals": {
    "field": "field",
    "value": "value"
  }
}