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Add Publisher#merge(...) operators #2533

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Mar 7, 2023
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Add Publisher#merge(...) operators #2533

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d973281
Add Publisher#mergeWith operators
Scottmitch Mar 7, 2023
152aff5
use extends
Scottmitch Mar 7, 2023
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review comments
Scottmitch Mar 7, 2023
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javadoc
Scottmitch Mar 7, 2023
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229 changes: 229 additions & 0 deletions servicetalk-concurrent-api/src/main/java/io/servicetalk/concurrent/api/Publisher.java
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,7 @@
import static io.servicetalk.concurrent.internal.SubscriberUtils.deliverErrorFromSource;
import static io.servicetalk.utils.internal.DurationUtils.toNanos;
import static java.util.Objects.requireNonNull;
import static java.util.function.Function.identity;

/**
* An asynchronous computation that produces 0, 1 or more elements and may or may not terminate successfully or with
Expand Down Expand Up @@ -1521,6 +1522,78 @@ public final <R> Publisher<R> flatMapConcatIterable(Function<? super T, ? extend
return new PublisherConcatMapIterable<>(this, mapper);
}

/**
* Merge two {@link Publisher}s together. There is no guaranteed ordering of events emitted from the returned
* {@link Publisher}.
* <p>
* This method provides similar capabilities as expanding each result into a collection and concatenating each
* collection in sequential programming:
* <pre>{@code
* List<T> mergedResults = ...; // concurrent safe list
* for (T t : resultOfThisPublisher()) {
* futures.add(e.submit(() -> {
* return mergedResults.add(t);
* }));
* }
* for (T t : resultOfOtherPublisher()) {
* futures.add(e.submit(() -> {
* return mergedResults.add(t);
* }));
* }
* for (Future<R> future : futures) {
* future.get(); // Throws if the processing for this item failed.
* }
* return mergedResults;
* }</pre>
* @param other The {@link Publisher} to merge with.
* @return A {@link Publisher} which is the result of this {@link Publisher} and {@code other} merged together.
* @see <a href="https://reactivex.io/documentation/operators/merge.html">ReactiveX merge operator</a>
* @see #mergeDelayError(Publisher)
* @see #mergeAll(Publisher[])
*/
public final Publisher<T> merge(Publisher<? extends T> other) {
return from(this, other).flatMapMerge(identity(), 2);
}

/**
* Merge two {@link Publisher}s together. There is no guaranteed ordering of events emitted from the returned
* {@link Publisher}. If either {@link Publisher} fails the error propagation will be delayed until both terminate.
* <p>
* This method provides similar capabilities as expanding each result into a collection and concatenating each
* collection in sequential programming:
* <pre>{@code
* List<T> mergedResults = ...; // concurrent safe list
* for (T t : resultOfThisPublisher()) {
* futures.add(e.submit(() -> {
* return mergedResults.add(t);
* }));
* }
* for (T t : resultOfOtherPublisher()) {
* futures.add(e.submit(() -> {
* return mergedResults.add(t);
* }));
* }
* List<Throwable> errors = ...;
* for (Future<R> future : futures) {
* try {
* future.get(); // Throws if the processing for this item failed.
* } catch (Throwable cause) {
* errors.add(cause);
* }
* }
* throwExceptionIfNotEmpty(errors);
* return mergedResults;
* }</pre>
* @param other The {@link Publisher} to merge with,
* @return A {@link Publisher} which is the result of this {@link Publisher} and {@code other} merged together.
* @see <a href="https://reactivex.io/documentation/operators/merge.html">ReactiveX merge operator</a>
* @see #merge(Publisher)
* @see #mergeAllDelayError(Publisher[])
*/
public final Publisher<T> mergeDelayError(Publisher<? extends T> other) {
return from(this, other).flatMapMergeDelayError(identity(), 2, 2);
}

/**
* Invokes the {@code onSubscribe} {@link Consumer} argument when
* {@link Subscriber#onSubscribe(PublisherSource.Subscription)} is called for {@link Subscriber}s of the returned
Expand Down Expand Up @@ -4014,6 +4087,162 @@ public static <T> Publisher<T> defer(Supplier<? extends Publisher<? extends T>>
return new PublisherDefer<>(publisherSupplier);
}

/**
* Merge all {@link Publisher}s together. There is no guaranteed ordering of events emitted from the returned
* {@link Publisher}.
* <p>
* This method provides similar capabilities as expanding each result into a collection and concatenating each
* collection in sequential programming:
* <pre>{@code
* List<T> mergedResults = ...; // concurrent safe list
* for (T t : resultOfPublisher1()) {
* futures.add(e.submit(() -> {
* return mergedResults.add(t);
* }));
* }
* for (T t : resultOfOtherPublisher()) {
* futures.add(e.submit(() -> {
* return mergedResults.add(t);
* }));
* }
* for (Future<R> future : futures) {
* future.get(); // Throws if the processing for this item failed.
* }
* return mergedResults;
* }</pre>
* @param publishers The {@link Publisher}s to merge together.
* @param <T> Type of items emitted by the returned {@link Publisher}.
* @return A {@link Publisher} which is the result of this {@link Publisher} and {@code other} merged together.
* @see <a href="https://reactivex.io/documentation/operators/merge.html">ReactiveX merge operator</a>
* @see #mergeAll(int, Publisher[])
* @see #mergeAllDelayError(Publisher[])
*/
@SafeVarargs
public static <T> Publisher<T> mergeAll(Publisher<? extends T>... publishers) {
return from(publishers).flatMapMerge(identity());
}

/**
* Merge all {@link Publisher}s together. There is no guaranteed ordering of events emitted from the returned
* {@link Publisher}.
* <p>
* This method provides similar capabilities as expanding each result into a collection and concatenating each
* collection in sequential programming:
* <pre>{@code
* List<T> mergedResults = ...; // concurrent safe list
* for (T t : resultOfPublisher1()) {
* futures.add(e.submit(() -> {
* return mergedResults.add(t);
* }));
* }
* for (T t : resultOfOtherPublisher()) {
* futures.add(e.submit(() -> {
* return mergedResults.add(t);
* }));
* }
* for (Future<R> future : futures) {
* future.get(); // Throws if the processing for this item failed.
* }
* return mergedResults;
* }</pre>
* @param maxConcurrency The maximum amount of {@link Publisher}s from {@code publishers} to subscribe to
* concurrently.
* @param publishers The {@link Publisher}s to merge together.
* @param <T> Type of items emitted by the returned {@link Publisher}.
* @return A {@link Publisher} which is the result of this {@link Publisher} and {@code other} merged together.
* @see <a href="https://reactivex.io/documentation/operators/merge.html">ReactiveX merge operator</a>
* @see #mergeAllDelayError(int, Publisher[])
*/
@SafeVarargs
public static <T> Publisher<T> mergeAll(int maxConcurrency, Publisher<? extends T>... publishers) {
return from(publishers).flatMapMerge(identity(), maxConcurrency);
}

/**
* Merge all {@link Publisher}s together. There is no guaranteed ordering of events emitted from the returned
* {@link Publisher}. If any {@link Publisher} terminates in an error, the error propagation will be delayed until
* all terminate.
* <p>
* This method provides similar capabilities as expanding each result into a collection and concatenating each
* collection in sequential programming:
* <pre>{@code
* List<T> mergedResults = ...; // concurrent safe list
* for (T t : resultOfPublisher1()) {
* futures.add(e.submit(() -> {
* return mergedResults.add(t);
* }));
* }
* for (T t : resultOfOtherPublisher()) {
* futures.add(e.submit(() -> {
* return mergedResults.add(t);
* }));
* }
* List<Throwable> errors = ...;
* for (Future<R> future : futures) {
* try {
* future.get(); // Throws if the processing for this item failed.
* } catch (Throwable cause) {
* errors.add(cause);
* }
* }
* throwExceptionIfNotEmpty(errors);
* return mergedResults;
* }</pre>
* @param publishers The {@link Publisher}s to merge together.
* @param <T> Type of items emitted by the returned {@link Publisher}.
* @return A {@link Publisher} which is the result of this {@link Publisher} and {@code other} merged together.
* @see <a href="https://reactivex.io/documentation/operators/merge.html">ReactiveX merge operator</a>
* @see #mergeAllDelayError(int, Publisher[])
* @see #mergeAll(Publisher[])
*/
@SafeVarargs
public static <T> Publisher<T> mergeAllDelayError(Publisher<? extends T>... publishers) {
return from(publishers).flatMapMergeDelayError(identity());
}

/**
* Merge all {@link Publisher}s together. There is no guaranteed ordering of events emitted from the returned
* {@link Publisher}. If any {@link Publisher} terminates in an error, the error propagation will be delayed until
* all terminate.
* <p>
* This method provides similar capabilities as expanding each result into a collection and concatenating each
* collection in sequential programming:
* <pre>{@code
* List<T> mergedResults = ...; // concurrent safe list
* for (T t : resultOfPublisher1()) {
* futures.add(e.submit(() -> {
* return mergedResults.add(t);
* }));
* }
* for (T t : resultOfOtherPublisher()) {
* futures.add(e.submit(() -> {
* return mergedResults.add(t);
* }));
* }
* List<Throwable> errors = ...;
* for (Future<R> future : futures) {
* try {
* future.get(); // Throws if the processing for this item failed.
* } catch (Throwable cause) {
* errors.add(cause);
* }
* }
* throwExceptionIfNotEmpty(errors);
* return mergedResults;
* }</pre>
* @param maxConcurrency The maximum amount of {@link Publisher}s from {@code publishers} to subscribe to
* concurrently.
* @param publishers The {@link Publisher}s to merge together.
* @param <T> Type of items emitted by the returned {@link Publisher}.
* @return A {@link Publisher} which is the result of this {@link Publisher} and {@code other} merged together.
* @see <a href="https://reactivex.io/documentation/operators/merge.html">ReactiveX merge operator</a>
* @see #mergeAll(Publisher[])
*/
@SafeVarargs
public static <T> Publisher<T> mergeAllDelayError(int maxConcurrency, Publisher<? extends T>... publishers) {
return from(publishers).flatMapMergeDelayError(identity(), maxConcurrency);
}

//
// Static Utility Methods End
//
Expand Down
5 changes: 5 additions & 0 deletions ...alk-concurrent-api/src/main/java/io/servicetalk/concurrent/api/PublisherFlatMapMerge.java
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,7 @@
import static io.servicetalk.concurrent.internal.ConcurrentUtils.tryAcquireLock;
import static io.servicetalk.concurrent.internal.SubscriberUtils.checkDuplicateSubscription;
import static io.servicetalk.concurrent.internal.SubscriberUtils.isRequestNValid;
import static io.servicetalk.concurrent.internal.SubscriberUtils.newExceptionForInvalidRequestN;
import static io.servicetalk.concurrent.internal.TerminalNotification.complete;
import static io.servicetalk.concurrent.internal.TerminalNotification.error;
import static io.servicetalk.utils.internal.PlatformDependent.newUnboundedMpscQueue;
Expand Down Expand Up @@ -175,6 +176,10 @@ public void request(final long n) {
incMappedDemand(n);
} else {
subscription.request(n);
// If the upstream source has already sent an onComplete signal, it won't be able to send an error.
// We propagate invalid demand upstream to clean-up upstream (if necessary) and force an error here to
// ensure we see an error.
enqueueAndDrain(error(newExceptionForInvalidRequestN(n)));
}
}

Expand Down
5 changes: 5 additions & 0 deletions ...lk-concurrent-api/src/main/java/io/servicetalk/concurrent/api/PublisherFlatMapSingle.java
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,7 @@
import static io.servicetalk.concurrent.internal.ConcurrentUtils.tryAcquireLock;
import static io.servicetalk.concurrent.internal.SubscriberUtils.checkDuplicateSubscription;
import static io.servicetalk.concurrent.internal.SubscriberUtils.isRequestNValid;
import static io.servicetalk.concurrent.internal.SubscriberUtils.newExceptionForInvalidRequestN;
import static io.servicetalk.concurrent.internal.TerminalNotification.complete;
import static io.servicetalk.concurrent.internal.TerminalNotification.error;
import static io.servicetalk.utils.internal.PlatformDependent.newUnboundedMpscQueue;
Expand Down Expand Up @@ -161,6 +162,10 @@ public void request(long n) {
}
} else {
subscription.request(n);
// If the upstream source has already sent an onComplete signal, it won't be able to send an error.
// We propagate invalid demand upstream to clean-up upstream (if necessary) and force an error here to
// ensure we see an error.
enqueueAndDrain(error(newExceptionForInvalidRequestN(n)));
}
}

Expand Down
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