Class AsyncNonBlockingStore<K,​V>

  • Type Parameters:
    K - key type for the store
    V - value type for the store
    All Implemented Interfaces:
    NonBlockingStore<K,​V>

    public class AsyncNonBlockingStore<K,​V>
    extends DelegatingNonBlockingStore<K,​V>
    A delegating NonBlockingStore implementation that batches write operations and runs the resulting batches on the delegate store in a non overlapping manner. That is that only a single batch will be running at a time.

    Whenever a write operation is performed it will also attempt to start a batch write immediately to the delegate store. Any concurrent writes during this time may be included in the batch. Any additional writes will be enqueued until the batch completes in which case it will automatically submit the pending batch, if there is one. Write operations to the same key in the same batch will be coalesced with only the last write being written to the underlying store. If the number of enqueued pending write operations becomes equal or larger than the modification queue, then any subsequent write will be added to the queue, but the returned Stage will not complete until the current batch completes in an attempt to provide some backpressure to slow writes.

    Read operations may be resolved by this store immediately if the given key is still being updated in the delegate store or if it is enqueued for the next batch. If the key is in neither it will query the underlying store to acquire it.

    Since:
    11.0
    Author:
    wburns
    • Constructor Detail

      • AsyncNonBlockingStore

        public AsyncNonBlockingStore​(NonBlockingStore<K,​V> actual)
    • Method Detail

      • start

        public CompletionStage<Void> start​(InitializationContext ctx)
        Description copied from interface: NonBlockingStore
        The first method to invoke so that the store can be configured and additional steps, such as connecting through a socket or opening file descriptors, are performed.

        The provided InitializationContext contains many helpful objects, including the configuration of the cache and store, concurrency utilities such as BlockingManager or an executor reserved for non-blocking operations only InitializationContext.getNonBlockingExecutor().

        This method is guaranteed not to be invoked concurrently with other operations. This means other methods are not invoked on this store until after the returned Stage completes.

        It is expected that an implementation should be able to "restart" by invoking start a second time if NonBlockingStore.stop() has been invoked and allowed for its stage to complete.

        Specified by:
        start in interface NonBlockingStore<K,​V>
        Overrides:
        start in class DelegatingNonBlockingStore<K,​V>
        Parameters:
        ctx - initialization context used to initialize this store.
        Returns:
        a stage that, when complete, indicates that this store has started successfully.
      • stop

        public CompletionStage<Void> stop()
        Description copied from interface: NonBlockingStore
        This method is invoked when the cache is being shutdown. It is expected that all resources related to the store are freed when the returned stage is complete.

        This method is guaranteed not to be invoked concurrently with other operations. This means other methods are not invoked on this store until after the returned Stage completes.

        It is expected that an implementation should be able to "restart" by invoking NonBlockingStore.start(InitializationContext) a second time if stop has been invoked and allowed for its stage to complete.

        Specified by:
        stop in interface NonBlockingStore<K,​V>
        Overrides:
        stop in class DelegatingNonBlockingStore<K,​V>
        Returns:
        a stage that, when complete, indicates that this store has stopped.
      • publishEntries

        public org.reactivestreams.Publisher<MarshallableEntry<K,​V>> publishEntries​(IntSet segments,
                                                                                          Predicate<? super K> filter,
                                                                                          boolean includeValues)
        Description copied from interface: NonBlockingStore
        Publishes entries from this store that are in one of the provided segments and also pass the provided filter. The returned publisher must support being subscribed to any number of times. That is subsequent invocations of Publisher.subscribe(Subscriber) should provide independent views of the underlying entries to the Subscribers. Entries should not be retrieved until a given Subscriber requests them via the Subscription.request(long) method.

        Subscribing to the returned Publisher should not block the invoking thread. It is the responsibility of the store implementation to ensure this occurs. If however the store must block to perform an operation it is recommended to wrap your Publisher before returning with the BlockingManager.blockingPublisher(Publisher) method and it will handle subscription and observation on the blocking and non-blocking executors respectively.

        Summary of Characteristics Effects

        Characteristic Effect
        NonBlockingStore.Characteristic.BULK_READ This method is only invoked if the store has this characteristic.
        NonBlockingStore.Characteristic.EXPIRATION When set the returned publisher must not return expired entries.
        NonBlockingStore.Characteristic.SEGMENTABLE When this is not set or segmentation is disabled in the configuration, the segment parameter may be ignored.
        Specified by:
        publishEntries in interface NonBlockingStore<K,​V>
        Overrides:
        publishEntries in class DelegatingNonBlockingStore<K,​V>
        Parameters:
        segments - a set of segments to filter entries by. This will always be non-null.
        filter - a filter to filter the keys by. If this is null then no additional filtering should be done after segments.
        Returns:
        a publisher that provides the keys from the store.
      • publishKeys

        public org.reactivestreams.Publisher<K> publishKeys​(IntSet segments,
                                                            Predicate<? super K> filter)
        Description copied from interface: NonBlockingStore
        Publishes keys from this store that are in one of the provided segments and also pass the provided filter. The returned publisher must support being subscribed to any number of times. That is subsequent invocations of Publisher.subscribe(Subscriber) should provide independent views of the underlying keys to the Subscribers. Keys should not be retrieved until a given Subscriber requests them via the Subscription.request(long) method.

        Subscribing to the returned Publisher should not block the invoking thread. It is the responsibility of the store implementation to ensure this occurs. If however the store must block to perform an operation it is recommended to wrap your Publisher before returning with the BlockingManager.blockingPublisher(Publisher) method and it will handle subscription and observation on the blocking and non-blocking executors respectively.

        Summary of Characteristics Effects

        Characteristic Effect
        NonBlockingStore.Characteristic.BULK_READ This method is only invoked if the store has this characteristic.
        NonBlockingStore.Characteristic.EXPIRATION When set the returned publisher must not return expired keys.
        NonBlockingStore.Characteristic.SEGMENTABLE When this is not set or segmentation is disabled in the configuration, the segment parameter may be ignored.

        Specified by:
        publishKeys in interface NonBlockingStore<K,​V>
        Overrides:
        publishKeys in class DelegatingNonBlockingStore<K,​V>
        Parameters:
        segments - a set of segments to filter keys by. This will always be non-null.
        filter - a filter to filter the keys by. If this is null then no additional filtering should be done after segments.
        Returns:
        a publisher that provides the keys from the store.
      • batch

        public CompletionStage<Void> batch​(int publisherCount,
                                           org.reactivestreams.Publisher<NonBlockingStore.SegmentedPublisher<Object>> removePublisher,
                                           org.reactivestreams.Publisher<NonBlockingStore.SegmentedPublisher<MarshallableEntry<K,​V>>> writePublisher)
        Description copied from interface: NonBlockingStore
        Writes and removes the entries provided by the Publishers into the store. Both are provided in the same method so that a batch may be performed as a single atomic operation if desired, although it is up to the store to manage its batching. If needed a store may generate batches of a configured size by using the StoreConfiguration.maxBatchSize() setting.

        Each of the Publishers may publish up to publisherCount publishers where each publisher is separated by the segment each entry maps to. Failure to request at least publisherCount publishers from the Publisher may cause a deadlock. Many reactive tools have methods such as flatMap that take an argument of how many concurrent subscriptions it manages, which is perfectly matched with this argument.

        WARNING: For performance reasons neither Publisher will emit any NonBlockingStore.SegmentedPublishers until both write and remove Publishers are subscribed to. These Publishers should also be only subscribed once.

        Summary of Characteristics Effects

        Characteristic Effect
        NonBlockingStore.Characteristic.READ_ONLY This method will never be invoked.
        NonBlockingStore.Characteristic.SEGMENTABLE If not set or segmentation is disabled in the configuration, the publisherCount parameter has a value of 1, which means there is only be one SegmentedPublisher to subscribe to.

        If a problem is encountered, it is recommended to wrap any created/caught Throwable in a PersistenceException and the stage be completed exceptionally.

        Specified by:
        batch in interface NonBlockingStore<K,​V>
        Overrides:
        batch in class DelegatingNonBlockingStore<K,​V>
        Parameters:
        publisherCount - the maximum number of SegmentPublishers either publisher will publish
        removePublisher - publishes what keys should be removed from the store
        writePublisher - publishes the entries to write to the store
        Returns:
        a stage that when complete signals that the store has written the values
      • delete

        public CompletionStage<Boolean> delete​(int segment,
                                               Object key)
        Description copied from interface: NonBlockingStore
        Removes the entry for given key and segment from the store and optionally report if the entry was actually removed or not.

        Summary of Characteristics Effects

        Characteristic Effect
        NonBlockingStore.Characteristic.READ_ONLY This method will never be invoked.
        NonBlockingStore.Characteristic.SEGMENTABLE When this is not set or segmentation is disabled in the configuration, the segment parameter may be ignored.

        If a problem is encountered, it is recommended to wrap any created/caught Throwable in a PersistenceException and the stage be completed exceptionally.

        Specified by:
        delete in interface NonBlockingStore<K,​V>
        Overrides:
        delete in class DelegatingNonBlockingStore<K,​V>
        Parameters:
        segment - the segment for the given key if segmentation is enabled, otherwise 0.
        key - key of the entry to delete from the store.
        Returns:
        a stage that completes with TRUE if the key existed in the store, FALSE if the key did not exist in the store, or null if the store does not report this information.
      • purgeExpired

        public org.reactivestreams.Publisher<MarshallableEntry<K,​V>> purgeExpired()
        Description copied from interface: NonBlockingStore
        Returns a Publisher that, after it is subscribed to, removes any expired entries from the store and publishes them to the returned Publisher.

        When the Publisher is subscribed to, it is expected to do point-in-time expiration and should not return a Publisher that has infinite entries or never completes.

        Subscribing to the returned Publisher should not block the invoking thread. It is the responsibility of the store implementation to ensure this occurs. If however the store must block to perform an operation it is recommended to wrap your Publisher before returning with the BlockingManager.blockingPublisher(Publisher) method and it will handle subscription and observation on the blocking and non-blocking executors respectively.

        Summary of Characteristics Effects

        Characteristic Effect
        NonBlockingStore.Characteristic.EXPIRATION This method is only invoked if the store has this characteristic.

        If a problem is encountered, it is recommended to wrap any created/caught Throwable in a PersistenceException and the stage be completed exceptionally.

        Specified by:
        purgeExpired in interface NonBlockingStore<K,​V>
        Overrides:
        purgeExpired in class DelegatingNonBlockingStore<K,​V>
        Returns:
        a Publisher that publishes the entries that are expired at the time of subscription.
      • removeSegments

        public CompletionStage<Void> removeSegments​(IntSet segments)
        Description copied from interface: NonBlockingStore
        Invoked when a node loses ownership of the given segments. A store must then remove any entries that map to the given segments and can remove any resources related to the given segments. For example, a database store can delete rows of the given segment or a file-based store can delete files related to the given segments.

        Summary of Characteristics Effects

        Characteristic Effect
        NonBlockingStore.Characteristic.SHAREABLE If the store has this characteristic and is configured to be shared, this method will never be invoked.
        NonBlockingStore.Characteristic.SEGMENTABLE This method is invoked only if the store has this characteristic and is configured to be segmented.

        If a problem is encountered, it is recommended to wrap any created/caught Throwable in a PersistenceException and the stage be completed exceptionally.

        Specified by:
        removeSegments in interface NonBlockingStore<K,​V>
        Overrides:
        removeSegments in class DelegatingNonBlockingStore<K,​V>
        Parameters:
        segments - the segments to remove.
        Returns:
        a stage that, when complete, indicates that the segments have been removed.
      • approximateSize

        public CompletionStage<Long> approximateSize​(IntSet segments)
        Description copied from interface: NonBlockingStore
        Returns an estimation of the amount of entries that map to the given segments in the store. This is similar to NonBlockingStore.size(IntSet) except that it is not strict about the returned size. For instance, this method might ignore if an entry is expired or if the store has some underlying optimizations to eventually have a consistent size.

        The implementations should be O(1). If a size approximation cannot be returned without iterating over all the entries in the store, the implementation should return -1L.

        Summary of Characteristics Effects

        Characteristic Effect
        NonBlockingStore.Characteristic.BULK_READ This method is only invoked if the store has this characteristic.
        NonBlockingStore.Characteristic.SEGMENTABLE When the store does not have this characteristic or segmentation is disabled in the configuration, the segment parameter is always IntSets.immutableRangeSet(numSegments).

        If a problem is encountered, it is recommended to wrap any created/caught Throwable in a PersistenceException and the stage be completed exceptionally.

        Specified by:
        approximateSize in interface NonBlockingStore<K,​V>
        Overrides:
        approximateSize in class DelegatingNonBlockingStore<K,​V>
        Parameters:
        segments - the segments for which the entries are counted.
        Returns:
        a stage that, when complete, contains the approximate count of the entries in the given segments, or -1L if an approximate count cannot be provided.
      • isAvailable

        public CompletionStage<Boolean> isAvailable()
        Description copied from interface: NonBlockingStore
        Returns a stage that, when complete, returns a boolean indicating whether the current store can be accessed for requests. This can be useful for store implementations that rely on an external source, such as a remote database, that may become unreachable. This can reduce sending requests to a store that is not available, as subsequent cache requests will result in a StoreUnavailableException being thrown until the store becomes available again.

        Store availability is polled periodically to update the status of stores if their availability changes. This method is not invoked concurrently with itself. In other words, this method is not invoked until after the previous stage has completed. However, this method is invoked concurrently with other operations, except for NonBlockingStore.start(InitializationContext) and NonBlockingStore.stop().

        If a store is configured to be StoreConfiguration.async() and the store becomes unavailable, then it is possible for the cache operations to be accepted in the interim period between the loss of availability and the modification-queue becoming full. This allows for this store to be unavailable for short periods of time without a StoreUnavailableException being thrown; however if the store does not become available before the queue fills, then a StoreUnavailableException is thrown.

        Specified by:
        isAvailable in interface NonBlockingStore<K,​V>
        Overrides:
        isAvailable in class DelegatingNonBlockingStore<K,​V>
        Returns:
        stage that, when complete, indicates if the store is available.