Package com.hazelcast.jet.grpc

Class GrpcServices

java.lang.Object

com.hazelcast.jet.grpc.GrpcServices

public final class GrpcServices
extends java.lang.Object

Provides ServiceFactory implementations for calling gRPC endpoints. The ServiceFactory created are designed to be used with the mapUsingServiceAsync transform.

Currently, two types of gRPC services are supported:

• unary
• bidirectionalStreamingService(SupplierEx, FunctionEx) (SupplierEx, FunctionEx) bidirectionalStreaming}

Since:

Jet 4.1

Method Summary

Modifier and Type	Method	Description
static <T,R> ServiceFactory<?,? extends GrpcService<T,R>>	bidirectionalStreamingService(SupplierEx<? extends io.grpc.ManagedChannelBuilder<?>> channelFn, FunctionEx<? super io.grpc.ManagedChannel,? extends FunctionEx<io.grpc.stub.StreamObserver<R>,io.grpc.stub.StreamObserver<T>>> callStubFn)	Creates a ServiceFactory that calls out to a bidirectional streaming gRPC service.
static <T,R> ServiceFactory<?,? extends GrpcService<T,R>>	unaryService(SupplierEx<? extends io.grpc.ManagedChannelBuilder<?>> channelFn, FunctionEx<? super io.grpc.ManagedChannel,? extends BiConsumerEx<T,io.grpc.stub.StreamObserver<R>>> callStubFn)	Creates a ServiceFactory that calls out to a unary gRPC service.

Methods inherited from class java.lang.Object

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

Method Detail

unaryService

@Nonnull
public static <T,R> ServiceFactory<?,? extends GrpcService<T,R>> unaryService(@Nonnull
                                                                                                SupplierEx<? extends io.grpc.ManagedChannelBuilder<?>> channelFn,
                                                                                                @Nonnull
                                                                                                FunctionEx<? super io.grpc.ManagedChannel,? extends BiConsumerEx<T,io.grpc.stub.StreamObserver<R>>> callStubFn)

Creates a ServiceFactory that calls out to a unary gRPC service.

For example, given the protobuf definition below:

 service Greeter {
   // Sends a greeting
   rpc SayHello (HelloRequest) returns (HelloReply) {}
 }
 

We can create the following service factory:

 ServiceFactory<?, ? extends GrpcService<HelloRequest, HelloResponse> greeterService = unaryService(
     () -> ManagedChannelBuilder.forAddress("localhost", 5000).usePlaintext(),
     channel -> GreeterGrpc.newStub(channel)::sayHello
 );
 

where GreeterGrpc is the class auto-generated by the protobuf compiler.

The created ServiceFactory should be used with the mapUsingServiceAsync transform as follows:

 Pipeline p = Pipeline.create();
 p.readFrom(TestSources.items("one", "two", "three", "four"))
     .mapUsingServiceAsync(greeterService, (service, input) -> {
         HelloRequest request = HelloRequest.newBuilder().setName(input).build();
        return service.call(request);
 })
  .writeTo(Sinks.logger());
 

The remote end can signal an error for a given input item. In that case the CompletableFuture returned from service.call(request) will be completed with that exception. To catch and handle it, use the CompletableFuture API.

Type Parameters:

T - type of the request object

R - type of the response object

Parameters:

channelFn - creates the channel builder. A single channel is created per processor instance.

callStubFn - a function which, given a channel, creates the stub and returns a function that calls the stub given the input item and the observer. It will be called once per input item.

bidirectionalStreamingService

@Nonnull
public static <T,R> ServiceFactory<?,? extends GrpcService<T,R>> bidirectionalStreamingService(@Nonnull
                                                                                                                 SupplierEx<? extends io.grpc.ManagedChannelBuilder<?>> channelFn,
                                                                                                                 @Nonnull
                                                                                                                 FunctionEx<? super io.grpc.ManagedChannel,? extends FunctionEx<io.grpc.stub.StreamObserver<R>,io.grpc.stub.StreamObserver<T>>> callStubFn)

Creates a ServiceFactory that calls out to a bidirectional streaming gRPC service. This may provide better throughput compared to the unary service because all communication happens within a single gRPC call, eliminating some overheads.

For example, given the protobuf definition below:

 service Greeter {
   // Sends a greeting
   rpc SayHello (stream HelloRequest) returns (stream HelloReply) {}
 }
 

We can create the following service factory:

 ServiceFactory<?, ? extends GrpcService<HelloRequest, HelloResponse> greeterService =
     bidirectionalStreamingService(
         () -> ManagedChannelBuilder.forAddress("localhost", 5000).usePlaintext(),
         channel -> GreeterGrpc.newStub(channel)::sayHello
 );
 

where GreeterGrpc is the auto-generated class by the protobuf compiler.

The created ServiceFactory should be used in the * used with the mapUsingServiceAsync transform as follows:

 Pipeline p = Pipeline.create();
 p.readFrom(TestSources.items("one", "two", "three", "four"))
     .mapUsingServiceAsync(greeterService, (service, input) -> {
         HelloRequest request = HelloRequest.newBuilder().setName(input).build();
        return service.call(request);
 })
  .writeTo(Sinks.logger());
 

The remote end can signal an error for a given input item. In that case the CompletableFuture returned from service.call(request) will be completed with that exception. To catch and handle it, use the CompletableFuture API.

Type Parameters:

T - type of the request object

R - type of the response object

Parameters:

channelFn - creates the channel builder. A single channel is created per processor instance.

callStubFn - a function which, given a channel, creates the stub and returns a function that calls the stub given the input item and the observer. It will be called once per input item.