AsyncFlatMapFunction (samza-api 1.9.0-SNAPSHOT API)
JavaScript is disabled on your browser.
Skip navigation links
Overview
Package
Class
Tree
Deprecated
Index
Help
Prev Class
Next Class
Frames
No Frames
All Classes
Summary: 
Nested | 
Field | 
Constr | 
Method
Detail: 
Field | 
Constr | 
Method
org.apache.samza.operators.functions
Interface AsyncFlatMapFunction<M,OM>
Type Parameters:
M - type of the input message
OM - type of the transformed messages
All Superinterfaces:
ClosableFunction, InitableFunction, java.io.Serializable
Functional Interface:
This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
@InterfaceStability.Unstable
@FunctionalInterface
public interface AsyncFlatMapFunction<M,OM>
extends InitableFunction, ClosableFunction, java.io.Serializable
Asynchronous variant of the FlatMapFunction used in tandem with MessageStream.flatMapAsync(AsyncFlatMapFunction)
to transform a collection of 0 or more messages.
Typically, AsyncFlatMapFunction is used for describing complex transformations that involve IO operations or remote calls.
The following pseudo code demonstrates a sample implementation of AsyncFlatMapFunction that sends out an email
and returns the status asynchronously.
AsyncFlatMapFunction<Email, Status> asyncEmailSender = (Email message) -> {
...
Request<Email> emailRequest = buildEmailRequest(message);
Future<EmailResponse> emailResponseFuture = emailClient.sendRequest(emailRequest); // send email asynchronously
...
return new CompletableFuture<>(emailResponseFuture)
.thenApply(response -> fetchStatus(response);
}
The function needs to be thread safe in case of task.max.concurrency>1. It also needs to coordinate any
shared state since happens-before is not guaranteed between the messages delivered to the function. Refer to
MessageStream.flatMapAsync(AsyncFlatMapFunction) docs for more details on the modes
and guarantees.
For each invocation, the CompletionStage returned by the function should be completed successfully/exceptionally
within task.callback.timeout.ms; failure to do so will result in SamzaException bringing down the application.
Method Summary
All Methods Instance Methods Abstract Methods 
Modifier and Type
Method and Description
java.util.concurrent.CompletionStage<java.util.Collection<OM>>
apply(M message)
Transforms the provided message into a collection of 0 or more messages.
Methods inherited from interface org.apache.samza.operators.functions.InitableFunction
init
Methods inherited from interface org.apache.samza.operators.functions.ClosableFunction
close
Method Detail
apply
java.util.concurrent.CompletionStage<java.util.Collection<OM>> apply(M message)
Transforms the provided message into a collection of 0 or more messages.
Parameters:
message - the input message to be transformed
Returns:
a CompletionStage of a Collection of transformed messages
Skip navigation links
Overview
Package
Class
Tree
Deprecated
Index
Help
Prev Class
Next Class
Frames
No Frames
All Classes
Summary: 
Nested | 
Field | 
Constr | 
Method
Detail: 
Field | 
Constr | 
Method