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/*
 * 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.flink.batch.connectors.cassandra;

import org.apache.flink.api.common.io.RichOutputFormat;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.streaming.connectors.cassandra.ClusterBuilder;
import org.apache.flink.streaming.connectors.cassandra.MapperOptions;
import org.apache.flink.util.Preconditions;

import com.datastax.driver.core.Cluster;
import com.datastax.driver.core.Session;
import com.datastax.driver.mapping.Mapper;
import com.datastax.driver.mapping.MappingManager;
import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;

/**
 * OutputFormat to write data to Apache Cassandra and from a custom Cassandra annotated object.
 *
 * @param  type of outputClass
 */
public class CassandraPojoOutputFormat extends RichOutputFormat {

    private static final Logger LOG = LoggerFactory.getLogger(CassandraPojoOutputFormat.class);
    private static final long serialVersionUID = -1701885135103942460L;

    private final ClusterBuilder builder;

    private final MapperOptions mapperOptions;
    private final Class outputClass;

    private transient Cluster cluster;
    private transient Session session;
    private transient Mapper mapper;
    private transient FutureCallback callback;
    private transient Throwable exception = null;

    public CassandraPojoOutputFormat(ClusterBuilder builder, Class outputClass) {
        this(builder, outputClass, null);
    }

    public CassandraPojoOutputFormat(
            ClusterBuilder builder, Class outputClass, MapperOptions mapperOptions) {
        Preconditions.checkNotNull(outputClass, "OutputClass cannot be null");
        Preconditions.checkNotNull(builder, "Builder cannot be null");
        this.builder = builder;
        this.mapperOptions = mapperOptions;
        this.outputClass = outputClass;
    }

    @Override
    public void configure(Configuration parameters) {
        this.cluster = builder.getCluster();
    }

    /**
     * Opens a Session to Cassandra and initializes the prepared statement.
     *
     * @param taskNumber The number of the parallel instance.
     */
    @Override
    public void open(int taskNumber, int numTasks) {
        this.session = cluster.connect();
        MappingManager mappingManager = new MappingManager(session);
        this.mapper = mappingManager.mapper(outputClass);
        if (mapperOptions != null) {
            Mapper.Option[] optionsArray = mapperOptions.getMapperOptions();
            if (optionsArray != null) {
                mapper.setDefaultSaveOptions(optionsArray);
            }
        }
        this.callback =
                new FutureCallback() {
                    @Override
                    public void onSuccess(Void ignored) {
                        onWriteSuccess();
                    }

                    @Override
                    public void onFailure(Throwable t) {
                        onWriteFailure(t);
                    }
                };
    }

    @Override
    public void writeRecord(OUT record) throws IOException {
        if (exception != null) {
            throw new IOException("write record failed", exception);
        }

        ListenableFuture result = mapper.saveAsync(record);
        Futures.addCallback(result, callback);
    }

    /**
     * Callback that is invoked after a record is written to Cassandra successfully.
     *
     * Subclass can override to provide its own logic.
     */
    protected void onWriteSuccess() {}

    /**
     * Callback that is invoked when failing to write to Cassandra. Current implementation will
     * record the exception and fail the job upon next record.
     *
     * Subclass can override to provide its own failure handling logic.
     *
     * @param t the exception
     */
    protected void onWriteFailure(Throwable t) {
        exception = t;
    }

    /** Closes all resources used. */
    @Override
    public void close() {
        mapper = null;
        try {
            if (session != null) {
                session.close();
            }
        } catch (Exception e) {
            LOG.error("Error while closing session.", e);
        }

        try {
            if (cluster != null) {
                cluster.close();
            }
        } catch (Exception e) {
            LOG.error("Error while closing cluster.", e);
        }
    }
}