ClusterEventsTest.java

/*
 * Copyright (c) 2008 - 2013 10gen, Inc. <http://10gen.com>
 *
 * 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 tour;

import com.mongodb.MongoClient;
import com.mongodb.MongoClientOptions;
import com.mongodb.ReadPreference;
import com.mongodb.ServerAddress;
import com.mongodb.client.MongoCollection;
import com.mongodb.event.ClusterDescriptionChangedEvent;
import com.mongodb.event.ClusterEvent;
import com.mongodb.event.ClusterListener;
import com.mongodb.event.ClusterListenerAdapter;
import org.bson.Document;

import static java.util.Arrays.asList;

public class ClusterEventsTest {

    private static volatile boolean canWrite = false;
    private static ReadPreference readPreference = ReadPreference.secondary();
    private static volatile boolean canRead = true;

    public static void main(String[] args) throws InterruptedException {
        MongoClientOptions options =
                MongoClientOptions.builder()
                        .addClusterListener(new MyClusterListenerForWriteAvailability())
                        .addClusterListener(new MyClusterListenerForReadAvailability())
                        .build();

        MongoClient client = new MongoClient(asList(new ServerAddress(), new ServerAddress("localhost:27018")), options);

        MongoCollection<Document> collection = client.getDatabase("test").getCollection("test");

        new Thread(() -> {
            while (true) {
                if (canWrite) {
                    try {
                        collection.insertOne(new Document());
                    } catch (Exception e) {
                        System.out.println("Exception while writing: " + e);
                    }
                }
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    // ignore interruptions
                }
            }
        });

        new Thread(() -> {
            while (true) {
                if (canRead) {
                    try {
                        collection.withReadPreference(readPreference).find().first();
                    } catch (Exception e) {
                        System.out.println("Exception while writing: " + e);
                    }
                }
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    // ignore interruptions
                }
            }
        });

        Thread.sleep(Long.MAX_VALUE);
    }

    private static class MyClusterListenerForWriteAvailability extends ClusterListenerAdapter {
        @Override
        public void clusterDescriptionChanged(final ClusterDescriptionChangedEvent event) {
            boolean couldWrite = canWrite;
            canWrite = !event.getClusterDescription().getPrimaries().isEmpty();
            if (couldWrite && !canWrite) {
                System.out.println("CAN'T WRITE ANYMORE!!");
            } else if (!couldWrite && canWrite) {
                System.out.println("CAN WRITE NOW!!!");
            }
        }
    }

    private static class MyClusterListenerForReadAvailability extends ClusterListenerAdapter {
        @Override
        public void clusterDescriptionChanged(final ClusterDescriptionChangedEvent event) {
            boolean couldRead = canRead;
            canRead = !readPreference.choose(event.getClusterDescription()).isEmpty();
            if (couldRead && !canRead) {
                System.out.println("CAN'T READ ANYMORE!!");
            } else if (!couldRead && canRead) {
                System.out.println("CAN READ NOW!!!");
            }
        }
    }
}