org.apache.beam.io.requestresponse

Class RequestResponseIO<RequestT,ResponseT>

java.lang.Object

org.apache.beam.sdk.transforms.PTransform<PCollection<RequestT>,RequestResponseIO.Result<ResponseT>>

org.apache.beam.io.requestresponse.RequestResponseIO<RequestT,ResponseT>

All Implemented Interfaces:

java.io.Serializable, HasDisplayData

public class RequestResponseIO<RequestT,ResponseT>
extends PTransform<PCollection<RequestT>,RequestResponseIO.Result<ResponseT>>

PTransform for reading from and writing to Web APIs.

RequestResponseIO is recommended for interacting with external systems that offer RPCs that execute relatively quickly and do not offer advance features to make RPC execution efficient.

For systems that offer features for more efficient reading, for example, tracking progress of RPCs, support for splitting RPCs (deduct two or more RPCs which when combined return the same result), consider using the Apache Beam's `Splittable DoFn` interface instead.

Basic Usage

RequestResponseIO minimally requires implementing the Caller interface:

 class MyCaller implements Caller<SomeRequest, SomeResponse> {
    public SomeResponse call(SomeRequest request) throws UserCodeExecutionException {
      // calls the API submitting SomeRequest payload and returning SomeResponse
    }
 }

Then provide RequestResponseIO's #create method your Caller implementation.

  PCollection<SomeRequest> requests = ...
  Result result = requests.apply(RequestResponseIO.create(new MyCaller()));
  result.getResponses().apply( ... );
  result.getFailures().apply( ... );
 

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	RequestResponseIO.Result<ResponseT> The RequestResponseIO.Result of processing request PCollection into response PCollection using custom Caller code.

Field Summary

Fields inherited from class org.apache.beam.sdk.transforms.PTransform

annotations, name, resourceHints

Method Summary

Modifier and Type	Method and Description
RequestResponseIO.Result<ResponseT>	expand(PCollection<RequestT> input) Override this method to specify how this PTransform should be expanded on the given InputT.
static <RequestT,ResponseT> RequestResponseIO<RequestT,ResponseT>	of(Caller<RequestT,ResponseT> caller)

Methods inherited from class org.apache.beam.sdk.transforms.PTransform

addAnnotation, compose, compose, getAdditionalInputs, getAnnotations, getDefaultOutputCoder, getDefaultOutputCoder, getDefaultOutputCoder, getKindString, getName, getResourceHints, populateDisplayData, setResourceHints, toString, validate, validate

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

of

public static <RequestT,ResponseT> RequestResponseIO<RequestT,ResponseT> of(Caller<RequestT,ResponseT> caller)

expand

public RequestResponseIO.Result<ResponseT> expand(PCollection<RequestT> input)

Description copied from class: PTransform

Override this method to specify how this PTransform should be expanded on the given InputT.

NOTE: This method should not be called directly. Instead apply the PTransform should be applied to the InputT using the apply method.

Composite transforms, which are defined in terms of other transforms, should return the output of one of the composed transforms. Non-composite transforms, which do not apply any transforms internally, should return a new unbound output and register evaluators (via backend-specific registration methods).

Specified by:

expand in class PTransform<PCollection<RequestT>,RequestResponseIO.Result<ResponseT>>