Using NoSQLSubscription

oracle.kv.pubsub.NoSQLSubscription is used to control your subscription. It is used to request operations from the subscribed tables, to perform checkpoints, terminate the stream, and so forth. It is used as a part of your NoSQLSubscriber implementation.

The NoSQLSubscription interface extends org.reactivestreams.Subscription, so it is sufficient for your NoSQLSubscription implementation class to extend NoSQLSubscription. When your implementation class implements NoSQLSubscriber.onSubscribe(), you will usually call NoSQLSubscription.request(), which asks for an initial set number of events to be delivered to the subscriber (these are consumed using NoSQLSubscriber.onNext()):

...
private NoSQLSubscription subscription;
...

@Override
public void onSubscribe(Subscription s) {
    subscription = (NoSQLSubscription) s;
    // request 100 store operations be streamed to this
    // subscriber.
    s.request(100);
    } 

The important actions that you can take with your NoSQLSubscription object are:

• Cancel the stream using NoSQLSubscription.cancel().

• Request more operations from the subscribed table.

  If you want to stream infinite number of operations, you can use Long.MAX_VALUE, which allows to stream for 584 years, assuming that the subscriber can process 1 billion operations per second.

  If the request is made at the beginning of the application's runtime before any operations have been consumed, then the operations will begin from the location identified by NoSQLSubscriptionConfig.setStreamMode(). If the request is made after operations have been consumed, then the operations will begin at the point in the stream immediately after the last consumed operation. For more information, see NoSQLStreamMode.

• Take a checkpoint. See Using Checkpoints for information about checkpoints.

• Get a list of currently subscribed tables anytime during the lifetime of the stream using NoSQLSubscription.getSubscribedTables() method. SubscriptionFailureException would be raised if the subscription is canceled or has shut down.

• Add a table to the running subscription stream asynchronously using NoSQLSubscription.subscribeTable() method. The change result will be signaled via the callback NoSQLSubscriber.onChangeResult() method.

• Remove a table from the running subscription stream asynchronously using NoSQLSubscription.unsubscribeTable() method. The change result will be signaled via the callback NoSQLSubscriber.onChangeResult() method.

For a complete list of operations supported by NoSQLSubscription, see NoSQLSubscription in the Java Direct Driver API Reference.