org.infinispan.persistence.spi

Interface NonBlockingStore<K,V>

Type Parameters:

K - key value type

V - value value type

All Known Implementing Classes:

AsyncNonBlockingStore, DelegatingNonBlockingStore, NonBlockingStoreAdapter

@Experimental
public interface NonBlockingStore<K,V>

The contract for defining how caches interface with external sources of data, such as databases or filesystems. As the name implies, any method in this class must never block the invoking thread.

The first method invoked on this store is start(InitializationContext), which starts the store. Once the returned stage has completed, the store is assumed to be in working state and ready to handle operations. Infinispan guarantees the visibility of variables written during the start method, so you do not need to synchronize them manually unless they are mutated in the normal operations of the store itself.

After the store starts, Infinispan uses the characteristics() method to query the characteristics of the store. It is highly recommended that this method never change the values it returns after the store starts because characteristics might not be cached. For more information, see NonBlockingStore.Characteristic and its various values.

By default, this interface has only a few required methods. If you implement any of the optional methods, ensure that you advertise the appropriate characteristic for that method so that Infinispan invokes it. If Infinispan is instructed that a characteristic is available and the method is not overridden, an UnsupportedOperationException will be thrown when trying to invoke the appropriate method. Each NonBlockingStore.Characteristic defines what methods map to which characteristic.

Although recommended, segmentation support in store implementations is optional. Segment parameters are provided for all methods where segment information is required, for example load(int, Object) and #publishEntries(IntSet, Predicate, boolean). If your store implementation does not support segmentation, you can ignore these parameters. However, you should note that segmented stores allow Infinispan caches to more efficiently perform bulk operations such as {@code Cache.size()} or {@code Cache.entrySet().stream()}. Segmentation also decreases the duration of state transfers when {@link PersistenceConfiguration#fetchPersistentState()} is enabled, as well as the time required to remove data by segments. To indicate that a store implementation supports segmentation, the {@link Characteristic#SEGMENTABLE} characteristic must be returned by the {@link #characteristics()} method. Store implementations can determine if stores are configured to be segmented if {@link StoreConfiguration#segmented()} is enabled, which is available from the {@code InitializationContext}.

Store implementations might need to interact with blocking APIs to perform their required operations. However the invoking thread must never be blocked, so Infinispan provides a {@link org.infinispan.util.concurrent.BlockingManager} utility class that handles blocking operations to ensure that they do not leak into the internal system. {@code BlockingManager} does this by running any blocking operations on blocking threads, while any stages continue on non-blocking threads.

This utility class provides different methods that range from equivalents for commonly used methods, such as {@link java.util.concurrent.CompletableFuture#supplyAsync(Supplier, Executor)}, to a wrapper around a {@link Publisher} that ensures it is subscribed and obversed on the correct threads. To obtain a {@code BlockingManager}, invoke the {@link InitializationContext#getBlockingManager()} method on the provided context in the start method.

Implementations of this store must be thread safe if concurrent operations are performed on it. The one exception is that {@link #start(InitializationContext)} and {@link #stop()} are not invoked concurrently with other operations.

Note that this interface is Experimental and its methods may change slightly over time until it has matured.

Since:

11.0

Author:

William Burns

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	NonBlockingStore.Characteristic Enumeration defining the various characteristics of the underlying store to communicate what features it may or may not support.
static interface	NonBlockingStore.SegmentedPublisher<Type> A Publisher that provides a stream of values and the segments to which those values map.

Method Summary

Modifier and Type	Method and Description
default CompletionStage<Void>	addSegments(IntSet segments) Invoked when a node becomes an owner of the given segments.
default CompletionStage<Long>	approximateSize(IntSet segments) Returns an estimation of the amount of entries that map to the given segments in the store.
default CompletionStage<Void>	batch(int publisherCount, org.reactivestreams.Publisher<NonBlockingStore.SegmentedPublisher<Object>> removePublisher, org.reactivestreams.Publisher<NonBlockingStore.SegmentedPublisher<MarshallableEntry<K,V>>> writePublisher) Writes and removes the entries provided by the Publishers into the store.
default Set<NonBlockingStore.Characteristic>	characteristics() Returns a set of characteristics for this store and its elements.
CompletionStage<Void>	clear() Clears all entries from the store.
default CompletionStage<Void>	commit(Transaction transaction) Commit changes in the provided transaction to the underlying store.
default CompletionStage<Boolean>	containsKey(int segment, Object key) Returns a stage that will contain whether the value can be found in the store.
CompletionStage<Boolean>	delete(int segment, Object key) Removes the entry for given key and segment from the store returning a stage that when completes normally contains whether the entry was actually removed or not.
default boolean	ignoreCommandWithFlags(long commandFlags) Some stores may not want to perform operations based on if a command has certain flags.
default CompletionStage<Boolean>	isAvailable() Returns a stage that, when complete, returns a boolean indicating whether the current store can be accessed for requests.
CompletionStage<MarshallableEntry<K,V>>	load(int segment, Object key) Returns a stage that will contain the value loaded from the store.
default CompletionStage<Void>	prepareWithModifications(Transaction transaction, int publisherCount, org.reactivestreams.Publisher<NonBlockingStore.SegmentedPublisher<Object>> removePublisher, org.reactivestreams.Publisher<NonBlockingStore.SegmentedPublisher<MarshallableEntry<K,V>>> writePublisher) Write remove and put modifications to the store in the prepare phase, which should not yet persisted until the same transaction is committed via commit(Transaction) or they are discarded if the transaction is rolled back via rollback(Transaction).
default org.reactivestreams.Publisher<MarshallableEntry<K,V>>	publishEntries(IntSet segments, Predicate<? super K> filter, boolean includeValues) Publishes entries from this store that are in one of the provided segments and also pass the provided filter.
default org.reactivestreams.Publisher<K>	publishKeys(IntSet segments, Predicate<? super K> filter) Publishes keys from this store that are in one of the provided segments and also pass the provided filter.
default org.reactivestreams.Publisher<MarshallableEntry<K,V>>	purgeExpired() Returns a Publisher that, after it is subscribed to, removes any expired entries from the store and publishes them to the returned Publisher.
default CompletionStage<Void>	removeSegments(IntSet segments) Invoked when a node loses ownership of the given segments.
default CompletionStage<Void>	rollback(Transaction transaction) Roll back the changes from the provided transaction to the underlying store.
default CompletionStage<Long>	size(IntSet segments) Returns the amount of entries that map to the given segments in the store.
CompletionStage<Void>	start(InitializationContext ctx) 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.
CompletionStage<Void>	stop() This method is invoked when the cache is being shutdown.
CompletionStage<Void>	write(int segment, MarshallableEntry<? extends K,? extends V> entry) Writes the entry to the store for the given segment returning a stage that completes normally when it is finished.

Method Detail

start

CompletionStage<Void> start(InitializationContext ctx)

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 stop() has been invoked and allowed for its stage to complete.

Parameters:

ctx - initialization context used to initialize this store.

Returns:

a stage that, when complete, indicates that this store has started successfully.

stop

CompletionStage<Void> stop()

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 start(InitializationContext) a second time if stop has been invoked and allowed for its stage to complete.

Returns:

a stage that, when complete, indicates that this store has stopped.

characteristics

default Set<NonBlockingStore.Characteristic> characteristics()

Returns a set of characteristics for this store and its elements. This method may be invoked multiple times to determine which methods of the store can be used and how the data in the store can be handled.

Refer to NonBlockingStore.Characteristic and its values for descriptions of each characteristic for stores.

Returns:

the set of characteristics that this store supports.

isAvailable

default CompletionStage<Boolean> isAvailable()

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 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 start(InitializationContext) and 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.

Returns:

stage that, when complete, indicates if the store is available.

load

CompletionStage<MarshallableEntry<K,V>> load(int segment,
                                             Object key)

Returns a stage that will contain the value loaded from the store. If a MarshallableEntry needs to be created here, InitializationContext.getMarshallableEntryFactory() ()} and InitializationContext.getByteBufferFactory() should be used.

Summary of Characteristics Effects

Characteristic	Effect
NonBlockingStore.Characteristic.WRITE_ONLY	This method will never be invoked.
NonBlockingStore.Characteristic.EXPIRATION	When set this method must not return expired entries.
NonBlockingStore.Characteristic.SEGMENTABLE	When this is not set the provided 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.

Parameters:

segment - the segment for the given key if segmentation is enabled, otherwise 0.

key - key of the entry to load.

Returns:

a stage that, when complete, contains the store value or null if not present.

containsKey

default CompletionStage<Boolean> containsKey(int segment,
                                             Object key)

Returns a stage that will contain whether the value can be found in the store.

Summary of Characteristics Effects

Characteristic	Effect
NonBlockingStore.Characteristic.WRITE_ONLY	This method will never be invoked.
NonBlockingStore.Characteristic.EXPIRATION	When set this method must not return true if the entry was expired.
NonBlockingStore.Characteristic.SEGMENTABLE	When this is not set the provided 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.

Parameters:

segment - the segment for the given key if segmentation is enabled, otherwise 0.

key - key of the entry to check.

Returns:

a stage that, when complete, contains a boolean stating if the value is contained in the store.

write

CompletionStage<Void> write(int segment,
                            MarshallableEntry<? extends K,? extends V> entry)

Writes the entry to the store for the given segment returning a stage that completes normally when it is finished.

Summary of Characteristics Effects

Characteristic	Effect
NonBlockingStore.Characteristic.READ_ONLY	This method will never be invoked.
NonBlockingStore.Characteristic.EXPIRATION	When set, this method must store the expiration metadata.
NonBlockingStore.Characteristic.SEGMENTABLE	When set, this method must ensure the segment is stored with the entry.

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

Parameters:

segment - the segment for the given key if segmentation is enabled, otherwise 0.

entry - the entry to persist to the store.

Returns:

a stage that when complete indicates that the store has written the value.

delete

CompletionStage<Boolean> delete(int segment,
                                Object key)

Removes the entry for given key and segment from the store returning a stage that when completes normally contains whether 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 the provided 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.

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 when complete contains a boolean stating if the value was removed from the store.

addSegments

default CompletionStage<Void> addSegments(IntSet segments)

Invoked when a node becomes an owner of the given segments. Some store implementations may require initializing additional resources when a new segment is required. For example a store could store entries in a different file per segment.

Summary of Characteristics Effects

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

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

Parameters:

segments - the segments to add.

Returns:

a stage that, when complete, indicates that the segments have been added.

removeSegments

default CompletionStage<Void> removeSegments(IntSet segments)

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

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

Parameters:

segments - the segments to remove.

Returns:

a stage that, when complete, indicates that the segments have been removed.

clear

CompletionStage<Void> clear()

Clears all entries from the store.

Summary of Characteristics Effects

Characteristic	Effect
NonBlockingStore.Characteristic.READ_ONLY	This method will never be invoked.

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

Returns:

a stage that, when complete, indicates that the store has been cleared.

batch

default CompletionStage<Void> batch(int publisherCount,
                                    org.reactivestreams.Publisher<NonBlockingStore.SegmentedPublisher<Object>> removePublisher,
                                    org.reactivestreams.Publisher<NonBlockingStore.SegmentedPublisher<MarshallableEntry<K,V>>> writePublisher)

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 the write and remove Publisher are subscribed to. These Publishers should also be only subscribed to once.

Summary of Characteristics Effects

Characteristic	Effect
NonBlockingStore.Characteristic.READ_ONLY	This method will never be invoked.
NonBlockingStore.Characteristic.SEGMENTABLE	If not set, the provided 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.

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

size

default CompletionStage<Long> size(IntSet segments)

Returns the amount of entries that map to the given segments in the store.

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 this is not set the provided segments 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.

Parameters:

segments - the segments for which the entries are counted.

Returns:

a stage that, when complete, contains the count of how many entries are present for the given segments.

approximateSize

default CompletionStage<Long> approximateSize(IntSet segments)

Returns an estimation of the amount of entries that map to the given segments in the store. This is similar to 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.

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 this is not set the provided segments 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.

Parameters:

segments - the segments for which the entries are counted.

Returns:

a stage that, when complete, contains the count of how many entries are present for the given segments.

publishEntries

default org.reactivestreams.Publisher<MarshallableEntry<K,V>> publishEntries(IntSet segments,
                                                                             Predicate<? super K> filter,
                                                                             boolean includeValues)

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 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 the provided segments parameter may be ignored.

Parameters:

segments - a set of segments to filter entries by. This will always be non null.

filter - a filter to filter they 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

default org.reactivestreams.Publisher<K> publishKeys(IntSet segments,
                                                     Predicate<? super K> filter)

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 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 the provided segments parameter may be ignored.

Parameters:

segments - a set of segments to filter keys by. This will always be non null.

filter - a filter to filter they 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.

purgeExpired

default org.reactivestreams.Publisher<MarshallableEntry<K,V>> purgeExpired()

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.

Returns:

a Publisher that publishes the entries that are expired at the time of subscription.

prepareWithModifications

default CompletionStage<Void> prepareWithModifications(Transaction transaction,
                                                       int publisherCount,
                                                       org.reactivestreams.Publisher<NonBlockingStore.SegmentedPublisher<Object>> removePublisher,
                                                       org.reactivestreams.Publisher<NonBlockingStore.SegmentedPublisher<MarshallableEntry<K,V>>> writePublisher)

Write remove and put modifications to the store in the prepare phase, which should not yet persisted until the same transaction is committed via commit(Transaction) or they are discarded if the transaction is rolled back via rollback(Transaction).

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 the write and remove Publisher are subscribed to. These Publishers should also be only subscribed to once.

Summary of Characteristics Effects

Characteristic	Effect
NonBlockingStore.Characteristic.TRANSACTIONAL	This method is invoked only 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.

Parameters:

transaction - the current transactional context.

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

commit

default CompletionStage<Void> commit(Transaction transaction)

Commit changes in the provided transaction to the underlying store.

Summary of Characteristics Effects

Characteristic	Effect
NonBlockingStore.Characteristic.TRANSACTIONAL	This method is invoked only 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.

Parameters:

transaction - the current transactional context.

Returns:

a stage that, when completed, indicates that the transaction was committed.

rollback

default CompletionStage<Void> rollback(Transaction transaction)

Roll back the changes from the provided transaction to the underlying store.

Summary of Characteristics Effects

Characteristic	Effect
NonBlockingStore.Characteristic.TRANSACTIONAL	This method is invoked only 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.

Parameters:

transaction - the current transactional context.

Returns:

a stage that, when completed, indicates that the transaction was rolled back.

ignoreCommandWithFlags

@Experimental
default boolean ignoreCommandWithFlags(long commandFlags)

Some stores may not want to perform operations based on if a command has certain flags. This method is currently only used for testing single write operations. This method may be removed at any time as it is experimental, it is not recommended for end users to implement it.

Parameters:

commandFlags - the flags attributed to the command when performing the operation.

Returns:

whether the operation should occur.