Package io.smallrye.mutiny

Interface Uni<T>

    • Method Summary

      All Methods Static Methods Instance Methods Abstract Methods Default Methods Deprecated Methods 
      Modifier and Type Method Description
      UniAwait<T> await()
      Awaits (blocking the caller thread) until the item or a failure is emitted by the observed Uni.
      default Uni<T> cache()
      Deprecated.
      Use UniMemoize.indefinitely() instead
      default Uni<T> call​(java.util.function.Function<? super T,​Uni<?>> function)
      Produces a new Uni invoking the given @{code action} when the item event is received.
      default Uni<T> call​(java.util.function.Supplier<Uni<?>> supplier)
      Produces a new Uni invoking the given @{code action} when the item event is received, but ignoring it.
      default <O> Uni<O> chain​(java.util.function.Function<? super T,​Uni<? extends O>> mapper)
      Once the observed Uni emits an item, execute the given mapper.
      default <O> Uni<O> chain​(java.util.function.Supplier<Uni<? extends O>> supplier)
      Once the observed Uni emits an item, execute the given supplier.
      static UniCombine combine()
      Creates a new Uni combining several others unis such as all or any.
      UniConvert<T> convert()
      Converts an Uni to other types such as CompletionStage
      static UniCreate createFrom()
      Creates a new Uni from various sources such as CompletionStage, UniEmitter, direct values, Exception...
      Uni<T> emitOn​(java.util.concurrent.Executor executor)
      Produces a new Uni invoking the UniSubscriber.onItem(Object) and UniSubscriber.onFailure(Throwable) on the supplied Executor.
      default Uni<T> eventually​(java.lang.Runnable action)
      Execute an action after an item or a failure has been emitted.
      default <O> Uni<T> eventually​(java.util.function.Supplier<Uni<? extends O>> supplier)
      When this Uni emits an item or a failure, invoke a Uni supplier then invoke the supplied Uni.
      default <O> Uni<O> flatMap​(java.util.function.Function<? super T,​Uni<? extends O>> mapper)
      Transforms the received item asynchronously, forwarding the events emitted by another Uni produced by the given mapper.
      UniIfNoItem<T> ifNoItem()
      Produces a Uni reacting when a no item event is fired by the upstream uni during the specified time period.
      default Uni<T> invoke​(java.lang.Runnable callback)
      Produces a new Uni invoking the given callback when the item event is fired, but ignoring it.
      default Uni<T> invoke​(java.util.function.Consumer<? super T> callback)
      Produces a new Uni invoking the given callback when the item event is fired.
      Uni<T> log()
      Log events (onSubscribe, onItem, ...) as they come from the upstream or the subscriber, and derives the identifier from the upstream operator class "simple name".
      Uni<T> log​(java.lang.String identifier)
      Log events (onSubscribe, onItem, ...) as they come from the upstream or the subscriber.
      default <O> Uni<O> map​(java.util.function.Function<? super T,​? extends O> mapper)
      Transforms the item (potentially null) emitted by this Uni by applying a (synchronous) function to it.
      UniMemoize<T> memoize()
      Configure memoization of the Uni item or failure.
      UniOnCancel<T> onCancellation()
      Configures actions to be performed when the subscriber cancels the subscription.
      UniOnFailure<T> onFailure()
      Like onFailure(Predicate) but applied to all failures fired by the upstream uni.
      UniOnFailure<T> onFailure​(java.lang.Class<? extends java.lang.Throwable> typeOfFailure)
      Configures a type of failure filtering the failures on which the behavior (specified with the returned UniOnFailure) is applied.
      UniOnFailure<T> onFailure​(java.util.function.Predicate<? super java.lang.Throwable> predicate)
      Configures a predicate filtering the failures on which the behavior (specified with the returned UniOnFailure) is applied.
      UniOnItem<T> onItem()
      Configures the action to execute when the observed Uni emits the item (potentially null).
      UniOnItemOrFailure<T> onItemOrFailure()
      Configures the action to execute when the observed Uni emits either an item (potentially null)) or a failure.
      UniOnSubscribe<T> onSubscribe()
      Configures the action to execute when the observed Uni sends a UniSubscription.
      UniOnTerminate<T> onTermination()
      Configures actions to be performed on termination, that is, on item, on failure, or when the subscriber cancels the subscription.
      default <R> Uni<R> plug​(java.util.function.Function<Uni<T>,​Uni<R>> operatorProvider)
      Plug a user-defined operator that does not belong to the existing Mutiny API.
      UniRepeat<T> repeat()
      Allows configuring repeating behavior.
      default <O> Uni<O> replaceWith​(Uni<O> uni)
      Ignore the item emitted by this Uni and replace it with another value using a Uni.
      default <O> Uni<O> replaceWith​(java.util.function.Supplier<O> supplier)
      Ignore the item emitted by this Uni and replace it with another value using a Supplier.
      default <O> Uni<O> replaceWith​(O item)
      Ignore the item emitted by this Uni and replace it with another value.
      default Uni<T> replaceWithNull()
      Ignore the item emitted by this Uni and replace it with null.
      default Uni<java.lang.Void> replaceWithVoid()
      Ignore the item emitted by this Uni and replace it with null and type Void.
      Uni<T> runSubscriptionOn​(java.util.concurrent.Executor executor)
      When a subscriber subscribes to this Uni, executes the subscription to the upstream Uni on a thread from the given executor.
      default <O> O stage​(java.util.function.Function<Uni<T>,​O> stage)
      Allows structuring the pipeline by creating a logic separation:
      UniSubscribe<T> subscribe()
      Requests the Uni to start resolving the item and allows configuring how the signals are propagated (using a UniSubscriber, callbacks, or a CompletionStage.
      default java.util.concurrent.CompletableFuture<T> subscribeAsCompletionStage()
      Shortcut for UniSubscribe.asCompletionStage().
      Multi<T> toMulti()
      Creates an instance of Multi from this Uni.

    • Method Detail

      • createFrom

        static UniCreate createFrom()
        Creates a new Uni from various sources such as CompletionStage, UniEmitter, direct values, Exception...

        Examples: 

         
 Uni.createFrom().item(1); // Emit 1 at subscription time
 Uni.createFrom().item(() -> x); // Emit x at subscription time, the supplier is invoked for each subscription
 Uni.createFrom().completionStage(cs); // Emit the item from this completion stage
 Uni.createFrom().completionStage(() -> cs); // Emit the item from this completion stage, the stage is not created before subscription
 Uni.createFrom().failure(exception); // Emit the failure at subscription time
 Uni.createFrom().deferred(() -> Uni.from().value(x)); // Defer the uni creation until subscription. Each subscription can produce a different uni
 Uni.createFrom().item(null); // Emit null at subscription time
 Uni.createFrom().nothing(); // Create a Uni not emitting any signal
 Uni.createFrom().publisher(publisher); // Create a Uni from a Reactive Streams Publisher
        Returns:
        the factory used to create Uni instances.
        See Also:
        UniCreate

      • stage

        default <O> O stage​(java.util.function.Function<Uni<T>,​O> stage)
        Allows structuring the pipeline by creating a logic separation: 
         
     Uni uni = upstream
      .stage(u -> { ...})
      .stage(u -> { ...})
      .stage(u -> { ...})

        With `stage` you can structure and chain groups of processing.

        Type Parameters:
        O - the outcome type
        Parameters:
        stage - the function receiving this Uni as parameter and producing the outcome (can be a Uni or something else), must not be null.
        Returns:
        the outcome of the function.

      • combine

        static UniCombine combine()
        Creates a new Uni combining several others unis such as all or any.
        Returns:
        the factory use to combine the uni instances

      • subscribe

        UniSubscribe<T> subscribe()
        Requests the Uni to start resolving the item and allows configuring how the signals are propagated (using a UniSubscriber, callbacks, or a CompletionStage. Unlike await(), this method configures non-blocking retrieval of the item and failure.

        Examples: 

         
     Uni<String> uni = ...;

    Subscription sub = uni.subscribe().with( // The return subscription can be used to cancel the operation
              item -> {},           // Callback calls on item
              failure -> {}           // Callback calls on failure
    );

    UniSubscriber<String> myUniSubscriber = ...
    uni.subscribe().withSubscriber(myUniSubscriber); // Subscribes to the Uni with the passed subscriber

    CompletableFuture future = uni.subscribe().asCompletableFuture(); // Get a CompletionStage receiving the item or failure
    // Cancelling the returned future cancels the subscription.
        Returns:
        the object to configure the subscription.
        See Also:
        uni.await() for waiting (blocking the caller thread) until the resolution of the observed Uni.

      • subscribeAsCompletionStage

        default java.util.concurrent.CompletableFuture<T> subscribeAsCompletionStage()
        Shortcut for UniSubscribe.asCompletionStage().
        Returns:
        the completion stage receiving the items emitted by this Uni

      • await

        UniAwait<T> await()
        Awaits (blocking the caller thread) until the item or a failure is emitted by the observed Uni. If the observed uni fails, the failure is thrown. In the case of a checked exception, the exception is wrapped into a CompletionException.

        Examples: 

         
 Uni<T> uni = ...;
 T res = uni.await().indefinitely(); // Await indefinitely until it get the item.
 T res = uni.await().atMost(Duration.ofMillis(1000)); // Awaits at most 1s. After that, a TimeoutException is thrown
 Optional<T> res = uni.await().asOptional().indefinitely(); // Retrieves the item as an Optional, empty if the item is null
        Returns:
        the object to configure the retrieval.

      • onItem

        UniOnItem<T> onItem()
        Configures the action to execute when the observed Uni emits the item (potentially null).

        Examples: 

         
 Uni<T> uni = ...;
 uni.onItem().transform(x -> ...); // Transform the item into another item (~ map)
 uni.onItem().transformToUni(x -> ...); // Transform the item into a Uni (~ flatMap)
        Returns:
        the object to configure the action to execute when an item is emitted

      • onSubscribe

        UniOnSubscribe<T> onSubscribe()
        Configures the action to execute when the observed Uni sends a UniSubscription. The downstream don't have a subscription yet. It will be passed once the configured action completes.

        Example: 

         
 uni.onSubscribe().invoke(sub -> System.out.println("subscribed"));
 // Delay the subscription by 1 second (or until an asynchronous action completes)
 uni.onSubscribe().call(sub -> Uni.createFrom(1).onItem().delayIt().by(Duration.ofSecond(1)));
        Returns:
        the object to configure the action to execution on subscription.

      • onItemOrFailure

        UniOnItemOrFailure<T> onItemOrFailure()
        Configures the action to execute when the observed Uni emits either an item (potentially null)) or a failure. Unlike onItem() and onFailure() the action would handle both cases in on "go".
        Returns:
        the object to configure the action to execute when an item is emitted or when a failure is propagated.

      • onFailure

        UniOnFailure<T> onFailure()
        Like onFailure(Predicate) but applied to all failures fired by the upstream uni. It allows configuring the on failure behavior (recovery, retry...).
        Returns:
        a UniOnFailure on which you can specify the on failure action

      • onFailure

        UniOnFailure<T> onFailure​(java.util.function.Predicate<? super java.lang.Throwable> predicate)
        Configures a predicate filtering the failures on which the behavior (specified with the returned UniOnFailure) is applied.

        For instance, to only when an IOException is fired as failure you can use: uni.onFailure(IOException.class).recoverWithItem("hello")

        The fallback value (hello) will only be used if the upstream uni fire a failure of type IOException.

        Parameters:
        predicate - the predicate, null means applied to all failures
        Returns:
        a UniOnFailure configured with the given predicate on which you can specify the on failure action

      • onFailure

        UniOnFailure<T> onFailure​(java.lang.Class<? extends java.lang.Throwable> typeOfFailure)
        Configures a type of failure filtering the failures on which the behavior (specified with the returned UniOnFailure) is applied.

        For instance, to only when an IOException is fired as failure you can use: uni.onFailure(IOException.class).recoverWithItem("hello")

        The fallback value (hello) will only be used if the upstream uni fire a failure of type IOException.

        Parameters:
        typeOfFailure - the class of exception, must not be null
        Returns:
        a UniOnFailure configured with the given predicate on which you can specify the on failure action

      • ifNoItem

        UniIfNoItem<T> ifNoItem()
        Produces a Uni reacting when a no item event is fired by the upstream uni during the specified time period.

        This Uni detects if this Uni does not emit an item before the configured timeout.

        Examples: uni.ifNoItem().after(Duration.ofMillis(1000).fail() // Propagate a TimeOutException uni.ifNoItem().after(Duration.ofMillis(1000).recoverWithValue("fallback") // Inject a fallback item on timeout uni.ifNoItem().after(Duration.ofMillis(1000).on(myExecutor)... // Configure the executor calling on timeout actions uni.ifNoItem().after(Duration.ofMillis(1000).retry().atMost(5) // Retry five times

        Returns:
        the on timeout group

      • emitOn

        Uni<T> emitOn​(java.util.concurrent.Executor executor)
        Produces a new Uni invoking the UniSubscriber.onItem(Object) and UniSubscriber.onFailure(Throwable) on the supplied Executor.

        Instead of receiving the item event on the thread firing the event, this method influences the threading context to switch to a thread from the given executor.

        Parameters:
        executor - the executor to use, must not be null
        Returns:
        a new Uni

      • runSubscriptionOn

        Uni<T> runSubscriptionOn​(java.util.concurrent.Executor executor)
        When a subscriber subscribes to this Uni, executes the subscription to the upstream Uni on a thread from the given executor. As a result, the UniSubscriber.onSubscribe(UniSubscription) method will be called on this thread (except mentioned otherwise)
        Parameters:
        executor - the executor to use, must not be null
        Returns:
        a new Uni

      • memoize

        @Experimental("Memoization is an experimental feature at this stage")
UniMemoize<T> memoize()
        Configure memoization of the Uni item or failure.
        API Note:
        This is an experimental API
        Returns:
        the object to configure memoization

      • cache

        @Deprecated
default Uni<T> cache()
        Deprecated.
        Use UniMemoize.indefinitely() instead
        Caches the events (item or failure) of this Uni and replays it for all further UniSubscriber.
        Returns:
        the new Uni. Unlike regular Uni, re-subscribing to this Uni does not re-compute the outcome but replayed the cached events.

      • map

        default <O> Uni<O> map​(java.util.function.Function<? super T,​? extends O> mapper)
        Transforms the item (potentially null) emitted by this Uni by applying a (synchronous) function to it. This method is equivalent to uni.onItem().apply(x -> ...) For asynchronous composition, look at flatMap.
        Type Parameters:
        O - the output type
        Parameters:
        mapper - the mapper function, must not be null
        Returns:
        a new Uni computing an item of type <O>.

      • invoke

        default Uni<T> invoke​(java.util.function.Consumer<? super T> callback)
        Produces a new Uni invoking the given callback when the item event is fired. Note that the item can be null.

        If the callback throws an exception, this exception is propagated to the downstream as failure.

        This method is a shortcut on UniOnItem.invoke(Consumer)

        Parameters:
        callback - the callback, must not be null
        Returns:
        the new Uni

      • invoke

        default Uni<T> invoke​(java.lang.Runnable callback)
        Produces a new Uni invoking the given callback when the item event is fired, but ignoring it.

        If the callback throws an exception, this exception is propagated to the downstream as failure.

        This method is a shortcut on UniOnItem.invoke(Consumer)

        Parameters:
        callback - the callback, must not be null
        Returns:
        the new Uni

      • call

        default Uni<T> call​(java.util.function.Function<? super T,​Uni<?>> function)
        Produces a new Uni invoking the given @{code action} when the item event is received. Note that the received item can be null.

        Unlike invoke(Consumer), the passed function returns a Uni. When the produced Uni sends its item, this item is discarded, and the original item is forwarded downstream. If the produced Uni fails, the failure is propagated downstream. If the callback throws an exception, this exception is propagated downstream as failure.

        This method is a shortcut on UniOnItem.call(Function)

        Parameters:
        function - the function taking the item and returning a Uni, must not be null, must not return null
        Returns:
        the new Uni

      • call

        default Uni<T> call​(java.util.function.Supplier<Uni<?>> supplier)
        Produces a new Uni invoking the given @{code action} when the item event is received, but ignoring it.

        Unlike invoke(Consumer), the passed function returns a Uni. When the produced Uni sends its item, this item is discarded, and the original item is forwarded downstream. If the produced Uni fails, the failure is propagated downstream. If the callback throws an exception, this exception is propagated downstream as failure.

        This method is a shortcut on UniOnItem.call(Function)

        Parameters:
        supplier - the supplier taking the item and returning a Uni, must not be null, must not return null
        Returns:
        the new Uni

      • flatMap

        default <O> Uni<O> flatMap​(java.util.function.Function<? super T,​Uni<? extends O>> mapper)
        Transforms the received item asynchronously, forwarding the events emitted by another Uni produced by the given mapper.

        The mapper is called with the item event of the current Uni and produces an Uni, possibly using another type of item (R). The events fired by produced Uni are forwarded to the Uni returned by this method.

        This operation is generally named flatMap. This method is a shortcut on UniOnItem.transformToUni(Function) onItem().transformToUni(mapper)}.

        Type Parameters:
        O - the type of item
        Parameters:
        mapper - the function called with the item of this Uni and producing the Uni, must not be null, must not return null.
        Returns:
        a new Uni that would fire events from the uni produced by the mapper function, possibly in an asynchronous manner.

      • chain

        default <O> Uni<O> chain​(java.util.function.Function<? super T,​Uni<? extends O>> mapper)
        Once the observed Uni emits an item, execute the given mapper. This mapper produces another Uni. The downstream receives the events emitted by this produced Uni. This operation allows chaining asynchronous operations: when the upstream completes with an item, run the mapper and emits the item (or failure) sent by the produced Uni: 
         Uni<Session> uni = getSomeSession();
 return uni.chain(session -> session.persist(fruit))
         .chain(session -> session.flush())
         .map(x -> Response.ok(fruit).status(201).build());
        The mapper is called with the item event of the current Uni and produces an Uni, possibly using another type of item (O). The events fired by produced Uni are forwarded to the Uni returned by this method.

        This operation is generally named flatMap. This method is a shortcut for onItem().transformToUni(mapper).

        Type Parameters:
        O - the type of item
        Parameters:
        mapper - the function called with the item of this Uni and producing the Uni, must not be null, must not return null.
        Returns:
        a new Uni that would fire events from the uni produced by the mapper function, possibly in an asynchronous manner.
        See Also:
        chain(Supplier)

      • chain

        default <O> Uni<O> chain​(java.util.function.Supplier<Uni<? extends O>> supplier)
        Once the observed Uni emits an item, execute the given supplier. This supplier produces another Uni. The downstream receives the events emitted by this produced Uni. This operation allows chaining asynchronous operations: when the upstream completes with an item, run the supplier and emits the item (or failure) sent by the produced Uni: 
         Uni<Session> uni = getSomeSession();
 return uni.chain(session -> session.persist(fruit))
         .chain(session -> session.flush())
         .chain(() -> server.close());
        The supplier ignores the item event of the current Uni and produces an Uni, possibly using another type of item (O). The events fired by produced Uni are forwarded to the Uni returned by this method.

        This method is a shortcut for UniOnItem.transformToUni(Function) onItem().transformToUni(ignored -> supplier.get()).

        Type Parameters:
        O - the type of item
        Parameters:
        supplier - the supplier producing the Uni, must not be null, must not return null.
        Returns:
        a new Uni that would fire events from the uni produced by the mapper function, possibly in an asynchronous manner.
        See Also:
        chain(Supplier)

      • eventually

        default Uni<T> eventually​(java.lang.Runnable action)
        Execute an action after an item or a failure has been emitted. This is equivalent to a finally block in Java. 
         
 String id = ...;
 Session session = getSomeSession();
 session.find(Fruit.class, id)
        .chain(fruit -> session.remove(fruit)
        .then(() -> session.flush())
        .eventually(() -> session.close());

        This method is a shortcut for UniOnItemOrFailure.invoke(BiConsumer): onItemOrFailure().invoke((item, err) -> action.run())

        Parameters:
        action - an action to perform, must not be null.
        Returns:
        a new Uni that emits events once the action has completed.
        See Also:
        onItemOrFailure()

      • eventually

        default <O> Uni<T> eventually​(java.util.function.Supplier<Uni<? extends O>> supplier)
        When this Uni emits an item or a failure, invoke a Uni supplier then invoke the supplied Uni. When the supplied Uni emits an item then it is ignored, and when it emits a failure it is reported.

        This is equivalent to a finally block in Java. 

         
 String id = ...;
 Session session = getSomeSession();
 session.find(Fruit.class, id)
        .chain(fruit -> session.remove(fruit)
        .eventually(() -> session.close());

        This method is a shortcut for UniOnItemOrFailure.call(BiFunction): onItemOrFailure().call((item, err) -> supplier.get())

        Type Parameters:
        O - the type of the item
        Parameters:
        supplier - a Uni supplier, cannot be null and cannot return null.
        Returns:
        a new Uni that emits events once the supplied Uni emits an item or a failure.
        See Also:
        onItemOrFailure()

      • convert

        UniConvert<T> convert()
        Converts an Uni to other types such as CompletionStage

        Examples: 

         
 uni.convert().toCompletionStage(); // Convert to CompletionStage using convenience method
 uni.convert().with(BuiltinConverters.toCompletionStage()); // Convert to CompletionStage using BuiltInConverters
 uni.convert().with(uni -> x); // Convert with a custom lambda converter
        Returns:
        the object to convert an Uni instance
        See Also:
        UniConvert

      • toMulti

        Multi<T> toMulti()
        Creates an instance of Multi from this Uni.

        When a subscriber subscribes to the returned Multi and request an item, it subscribes to this Uni and the events from this Uni are propagated to the Multi:

        • if this Uni emits a non-null item - this item is propagated to the Multi and followed with the completion event
        • if this Uni emits a null item - the Multi fires the completion event
        • if this Uni emits a failure, this failure event is propagated by the Multi

        It's important to note that the subscription to this Uni happens when the subscriber to the produced Multi requests items, and not at subscription time.

        Returns:
        the produced Multi, never null

      • repeat

        UniRepeat<T> repeat()
        Allows configuring repeating behavior. Repeating allow transforming a Uni into a Multi either a specific amount of times or indefinitely. Each time, a new subscription is attempted on the Uni. Cancelling the subscription stops the repeating behavior.
        Returns:
        the object to configure the repeating behavior.

      • onTermination

        UniOnTerminate<T> onTermination()
        Configures actions to be performed on termination, that is, on item, on failure, or when the subscriber cancels the subscription.
        Returns:
        the object to configure the termination actions.

      • onCancellation

        UniOnCancel<T> onCancellation()
        Configures actions to be performed when the subscriber cancels the subscription.
        Returns:
        the object to configure the cancellation actions.

      • plug

        default <R> Uni<R> plug​(java.util.function.Function<Uni<T>,​Uni<R>> operatorProvider)
        Plug a user-defined operator that does not belong to the existing Mutiny API.
        Type Parameters:
        R - the output type
        Parameters:
        operatorProvider - a function to create and bind a new operator instance, taking this Uni as a parameter and returning a new Uni. Must neither be null nor return null.
        Returns:
        the new Uni

      • replaceWith

        default <O> Uni<O> replaceWith​(O item)
        Ignore the item emitted by this Uni and replace it with another value.

        This is a shortcut for uni.onItem().transform(ignore -> item).

        Type Parameters:
        O - the output type
        Parameters:
        item - the replacement value
        Returns:
        the new Uni

      • replaceWith

        default <O> Uni<O> replaceWith​(java.util.function.Supplier<O> supplier)
        Ignore the item emitted by this Uni and replace it with another value using a Supplier.

        This is a shortcut for uni.onItem().transform(ignore -> supplier.get()).

        Type Parameters:
        O - the output type
        Parameters:
        supplier - the replacement value supplier
        Returns:
        the new Uni

      • replaceWith

        default <O> Uni<O> replaceWith​(Uni<O> uni)
        Ignore the item emitted by this Uni and replace it with another value using a Uni.

        This is a shortcut for uni.onItem().transformToUni(ignore -> uni).

        Type Parameters:
        O - the output type
        Parameters:
        uni - the replacement value Uni
        Returns:
        the new Uni

      • replaceWithNull

        default Uni<T> replaceWithNull()
        Ignore the item emitted by this Uni and replace it with null.

        This is a shortcut for uni.onItem().transform(ignore -> null).

        Returns:
        the new Uni

      • replaceWithVoid

        default Uni<java.lang.Void> replaceWithVoid()
        Ignore the item emitted by this Uni and replace it with null and type Void.

        This method is in effect similar to replaceWithNull(), except that it returns a Uni<Void> instead of a Uni<T>.

        This is a shortcut for uni.onItem().transform(ignored -> null).

        Returns:
        the new Uni

      • log

        Uni<T> log​(java.lang.String identifier)
        Log events (onSubscribe, onItem, ...) as they come from the upstream or the subscriber. Events will be logged as long as the Uni hasn't been cancelled or terminated. Logging is framework-agnostic and can be configured in the Infrastructure class.
        Parameters:
        identifier - an identifier of this operator to be used in log events
        Returns:
        a new Uni
        See Also:
        Infrastructure.setOperatorLogger(Infrastructure.OperatorLogger)