Reactive Spring Data Cassandra Experiment

ReactiveCqlTemplate.java

/*
 * Copyright 2016 the original author or authors.
 *
 * Licensed 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.springframework.cassandra.core;

import java.util.concurrent.CompletableFuture;

import org.springframework.beans.factory.DisposableBean;
import org.springframework.cassandra.support.CassandraAccessor;

import com.datastax.driver.core.ResultSet;
import com.datastax.driver.core.ResultSetFuture;
import com.datastax.driver.core.Row;
import com.datastax.driver.core.Session;
import com.datastax.driver.core.Statement;

import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import reactor.core.scheduler.Scheduler;
import reactor.core.scheduler.Schedulers;

/**
 * @author Mark Paluch
 */
public class ReactiveCqlTemplate extends CassandraAccessor implements DisposableBean {

	private Scheduler scheduler;

	@Override
	public void afterPropertiesSet() {

		super.afterPropertiesSet();
		scheduler = Schedulers.newElastic(getClass().getSimpleName());
	}

	@Override
	public void destroy() throws Exception {
		scheduler.shutdown();
	}

	public Mono<ResultSet> doWithSession(SessionCallback<ResultSetFuture> callback) {

		Session session = getSession();
		return Mono.defer(() -> {

			ResultSetFuture resultSetFuture = callback.doInSession(session);

			final CompletableFuture<ResultSet> future = new CompletableFuture<>();

			resultSetFuture.addListener(() -> {

				if (resultSetFuture.isDone()) {

					try {
						future.complete(resultSetFuture.getUninterruptibly());
					} catch (Exception e) {
						future.completeExceptionally(e);
					}
				}
			}, Runnable::run);

			return Mono.fromFuture(future);
		}).subscribeOn(scheduler);
	}

	/**
	 * Return a {@link Mono} that emits the {@link ResultSet}.
	 *
	 * @param cql
	 * @return
	 */
	public Mono<ResultSet> execute(String cql) {
		return doWithSession(s -> s.executeAsync(cql));
	}

	/**
	 * Return a {@link Flux} that emits {@link Row rows} from the result set.
	 *
	 * @param cql
	 * @return
	 */
	public Flux<Row> query(String cql) {
		return execute(cql).flatMap(rows -> Flux.fromIterable(rows));
	}

	/**
	 * Return a {@link Mono} that emits the {@link ResultSet}.
	 *
	 * @param statement
	 * @return
	 */
	public Mono<ResultSet> execute(Statement statement) {
		return doWithSession(s -> s.executeAsync(statement));
	}

	/**
	 * Return a {@link Flux} that emits {@link Row rows} from the result set.
	 * 
	 * @param statement
	 * @return
	 */
	public Flux<Row> query(Statement statement) {
		return execute(statement).flatMap(rows -> Flux.fromIterable(rows));
	}
}

RowPublisher.java

/*
 * Copyright 2016 the original author or authors.
 *
 * Licensed 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.springframework.cassandra.core;

import org.reactivestreams.Publisher;

import com.datastax.driver.core.ColumnDefinitions;
import com.datastax.driver.core.ExecutionInfo;
import com.datastax.driver.core.PagingState;
import com.datastax.driver.core.Row;

import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

/**
 * @author Mark Paluch
 */
public interface RowPublisher extends Publisher<Row> {

	/**
	 * Returns the columns returned in this RowPublisher.
	 *
	 * @return the columns returned in this RowPublisher.
	 */
	Mono<ColumnDefinitions> getColumnDefinitions();

	/**
	 * Returns the next paging state in this RowPublisher.
	 *
	 * @return the next paging state in this RowPublisher.
	 */
	Mono<PagingState> getPagingState();

	/**
	 * Returns the next paging state in this RowPublisher.
	 *
	 * @return the next paging state in this RowPublisher.
	 */
	Mono<PagingState> getNextPagingState();

	/**
	 * Returns information on the execution of the last query made for this RowPublisher.
	 *
	 * @return the execution info for the last query made for this RowPublisher.
	 */
	Mono<ExecutionInfo> getExecutionInfo();

	/**
	 * Return the execution information for all queries made to retrieve this RowPublisher.
	 *
	 *  @return a list of the execution info for all the queries made for this RowPublisher.
	 */
	Flux<ExecutionInfo> getAllExecutionInfo();

	/**
	 * If the query that produced this RowPublisher was a conditional update, return whether it was successfully applied.
	 */
	Mono<Boolean> wasApplied();
}