runners/java-fn-execution/src/test/java/org/apache/beam/runners/fnexecution/control/FnApiControlClientPoolServiceTest.java

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 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
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 *     http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.beam.runners.fnexecution.control;

import static org.hamcrest.Matchers.is;
import static org.junit.Assert.assertThat;
import static org.mockito.Matchers.any;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;

import com.google.common.util.concurrent.ListenableFuture;
import io.grpc.stub.StreamObserver;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.LinkedBlockingQueue;
import org.apache.beam.model.fnexecution.v1.BeamFnApi;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.JUnit4;

/** Unit tests for {@link FnApiControlClientPoolService}. */
@RunWith(JUnit4.class)
public class FnApiControlClientPoolServiceTest {

  // For ease of straight-line testing, we use a LinkedBlockingQueue; in practice a SynchronousQueue
  // for matching incoming connections and server threads is likely.
  private final BlockingQueue<FnApiControlClient> pool = new LinkedBlockingQueue<>();
  private FnApiControlClientPoolService controlService =
      FnApiControlClientPoolService.offeringClientsToPool(pool);

  @Test
  public void testIncomingConnection() throws Exception {
    StreamObserver<BeamFnApi.InstructionRequest> requestObserver = mock(StreamObserver.class);
    StreamObserver<BeamFnApi.InstructionResponse> responseObserver =
        controlService.control(requestObserver);

    FnApiControlClient client = pool.take();

    // Check that the client is wired up to the request channel
    String id = "fakeInstruction";
    ListenableFuture<BeamFnApi.InstructionResponse> responseFuture =
        client.handle(BeamFnApi.InstructionRequest.newBuilder().setInstructionId(id).build());
    verify(requestObserver).onNext(any(BeamFnApi.InstructionRequest.class));
    assertThat(responseFuture.isDone(), is(false));

    // Check that the response channel really came from the client
    responseObserver.onNext(
        BeamFnApi.InstructionResponse.newBuilder().setInstructionId(id).build());
    responseFuture.get();
  }
}