Several calls to the Google Ads API return long-running operations (LROs). These track
the status of a job that executes over an extended period of time without
requiring a single blocking RPC.

## OperationFuture class

You interact with LROs in the Java client library using the
[`OperationFuture`](https://cloud.google.com/java/docs/reference/gax/latest/overview.html) class. Because `OperationFuture` relies on the
underlying service client to poll the API for status updates, make sure that the
service client remains open and active until the operation completes.

Not recommended:

```java
private void executeOperation(String jobName) throws Exception {
  OperationFuture<Empty, OfflineUserDataJobMetadata> future =
      startLongRunningOperation(jobName);
  // FAILS: The service client was already closed when
  // startLongRunningOperation() exited its try-with-resources block, so
  // future.get() fails when polling.
  future.get();
}

private OperationFuture<Empty, OfflineUserDataJobMetadata>
    startLongRunningOperation(String jobToStart) {
  try (OfflineUserDataJobServiceClient offlineUserDataJobServiceClient =
      googleAdsClient
          .getLatestVersion()
          .createOfflineUserDataJobServiceClient()) {
    // Issues an asynchronous request to run the offline user data job.
    return offlineUserDataJobServiceClient.runOfflineUserDataJobAsync(
        jobToStart);
  }
}
```

Recommended:

```java
private void executeOperation(String jobName) throws Exception {
  try (OfflineUserDataJobServiceClient offlineUserDataJobServiceClient =
      googleAdsClient
          .getLatestVersion()
          .createOfflineUserDataJobServiceClient()) {
    OperationFuture<Empty, OfflineUserDataJobMetadata> future =
        startLongRunningOperation(offlineUserDataJobServiceClient, jobName);
    // Waits for the operation to complete (with a timeout) while the client is
    // still open.
    future.get(5, TimeUnit.MINUTES);
  }
}

private OperationFuture<Empty, OfflineUserDataJobMetadata>
    startLongRunningOperation(
        OfflineUserDataJobServiceClient offlineUserDataJobServiceClient,
        String jobToStart) {
  return offlineUserDataJobServiceClient.runOfflineUserDataJobAsync(jobToStart);
}
```

Notice how the `OperationFuture` is only used while the
`OfflineUserDataJobServiceClient` remains open within the `try-with-resources`
block.