content: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *    http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.arrow.flight.grpc;
  
  import io.grpc.Context;
  import java.util.Collection;
  import java.util.List;
  import java.util.concurrent.Callable;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Future;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.TimeoutException;
  import java.util.stream.Collectors;
  
  /**
   * An {@link ExecutorService} that propagates the {@link Context}.
   *
   * <p>Context is used to propagate per-call state, like the authenticated user, between threads (as
   * gRPC makes no guarantees about what thread things execute on). This wrapper makes it easy to
   * preserve this when using an Executor. The Context itself is immutable, so it is thread-safe.
   */
  public class ContextPropagatingExecutorService implements ExecutorService {
  
    private final ExecutorService delegate;
  
    public ContextPropagatingExecutorService(ExecutorService delegate) {
      this.delegate = delegate;
    }
  
    // These are just delegate methods.
  
    @Override
    public void shutdown() {
      delegate.shutdown();
    }
  
    @Override
    public List<Runnable> shutdownNow() {
      return delegate.shutdownNow();
    }
  
    @Override
    public boolean isShutdown() {
      return delegate.isShutdown();
    }
  
    @Override
    public boolean isTerminated() {
      return delegate.isTerminated();
    }
  
    @Override
    public boolean awaitTermination(long timeout, TimeUnit unit) throws InterruptedException {
      return delegate.awaitTermination(timeout, unit);
    }
  
    // These are delegate methods that wrap the submitted task in the current gRPC Context.
  
    @Override
    public <T> Future<T> submit(Callable<T> task) {
      return delegate.submit(Context.current().wrap(task));
    }
  
    @Override
    public <T> Future<T> submit(Runnable task, T result) {
      return delegate.submit(Context.current().wrap(task), result);
    }
  
    @Override
    public Future<?> submit(Runnable task) {
      return delegate.submit(Context.current().wrap(task));
    }
  
    @Override
    public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
        throws InterruptedException {
      return delegate.invokeAll(
          tasks.stream().map(Context.current()::wrap).collect(Collectors.toList()));
    }
  
    @Override
    public <T> List<Future<T>> invokeAll(
        Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)
        throws InterruptedException {
      return delegate.invokeAll(
          tasks.stream().map(Context.current()::wrap).collect(Collectors.toList()), timeout, unit);
    }
  
    @Override
    public <T> T invokeAny(Collection<? extends Callable<T>> tasks)
        throws InterruptedException, ExecutionException {
      return delegate.invokeAny(
          tasks.stream().map(Context.current()::wrap).collect(Collectors.toList()));
    }
  
    @Override
    public <T> T invokeAny(Collection<? extends Callable<T>> tasks, long timeout, TimeUnit unit)
        throws InterruptedException, ExecutionException, TimeoutException {
      return delegate.invokeAny(
          tasks.stream().map(Context.current()::wrap).collect(Collectors.toList()), timeout, unit);
    }
  
    @Override
    public void execute(Runnable command) {
      delegate.execute(Context.current().wrap(command));
    }
  }
  