org.apache.samza.table.remote.couchbase.CouchbaseTableReadFunction.java Source code

Java tutorial

Introduction

Here is the source code for org.apache.samza.table.remote.couchbase.CouchbaseTableReadFunction.java

Source

/*
 * 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.
 */
/*
 * 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.samza.table.remote.couchbase;

import com.couchbase.client.deps.io.netty.buffer.ByteBuf;
import com.couchbase.client.deps.io.netty.util.ReferenceCountUtil;
import com.couchbase.client.java.document.BinaryDocument;
import com.couchbase.client.java.document.Document;
import com.couchbase.client.java.document.JsonDocument;
import com.couchbase.client.java.document.json.JsonObject;
import com.google.common.base.Preconditions;
import java.util.NoSuchElementException;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.TimeUnit;
import org.apache.commons.lang3.StringUtils;
import org.apache.samza.SamzaException;
import org.apache.samza.context.Context;
import org.apache.samza.table.remote.TableReadFunction;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import rx.Single;
import rx.SingleSubscriber;

/**
 * TableReadFunction implementation for reading from Couchbase. The value type can be either {@link JsonObject} or
 * any other Object. If the value type is JsonObject, data in JSON format will be read from Couchbase directly as
 * JsonObject. Otherwise, a {@link org.apache.samza.serializers.Serde} needs to be provided to serialize and
 * deserialize the value object.
 * @param <V> Type of values to read from Couchbase
 */
public class CouchbaseTableReadFunction<V> extends BaseCouchbaseTableFunction<V>
        implements TableReadFunction<String, V> {
    private static final Logger LOGGER = LoggerFactory.getLogger(CouchbaseTableReadFunction.class);

    protected final Class<? extends Document<?>> documentType;

    /**
     * Construct an instance of {@link CouchbaseTableReadFunction}.
     * @param bucketName Name of the couchbase bucket
     * @param clusterNodes Some Hosts of the Couchbase cluster. Recommended to provide more than one nodes so that if
     *                     the first node could not be connected, other nodes can be tried.
     * @param valueClass Type of values
     */
    public CouchbaseTableReadFunction(String bucketName, Class<V> valueClass, String... clusterNodes) {
        super(bucketName, valueClass, clusterNodes);
        documentType = JsonObject.class.isAssignableFrom(valueClass) ? JsonDocument.class : BinaryDocument.class;
    }

    @Override
    public void init(Context context) {
        super.init(context);
        LOGGER.info("Read function for bucket {} initialized successfully", bucketName);
    }

    @Override
    public CompletableFuture<V> getAsync(String key) {
        Preconditions.checkArgument(StringUtils.isNotBlank(key), "key must not be null, empty or blank");
        CompletableFuture<V> future = new CompletableFuture<>();
        Single<? extends Document<?>> singleObservable = bucket.async()
                .get(key, documentType, timeout.toMillis(), TimeUnit.MILLISECONDS).toSingle();
        singleObservable.subscribe(new SingleSubscriber<Document<?>>() {
            @Override
            public void onSuccess(Document<?> document) {
                if (document != null) {
                    if (document instanceof BinaryDocument) {
                        handleGetAsyncBinaryDocument((BinaryDocument) document, future, key);
                    } else {
                        // V is of type JsonObject
                        future.complete((V) document.content());
                    }
                } else {
                    // The Couchbase async client should not return null
                    future.completeExceptionally(
                            new SamzaException(String.format("Got unexpected null value from key %s", key)));
                }
            }

            @Override
            public void onError(Throwable throwable) {
                if (throwable instanceof NoSuchElementException) {
                    // There is no element returned by the observable, meaning the key doesn't exist.
                    future.complete(null);
                } else {
                    future.completeExceptionally(
                            new SamzaException(String.format("Failed to get key %s", key), throwable));
                }
            }
        });
        return future;
    }

    /**
     * Helper method to read bytes from binaryDocument and release the buffer.
     */
    private void handleGetAsyncBinaryDocument(BinaryDocument binaryDocument, CompletableFuture<V> future,
            String key) {
        ByteBuf buffer = binaryDocument.content();
        try {
            byte[] bytes;
            if (buffer.hasArray() && buffer.arrayOffset() == 0 && buffer.readableBytes() == buffer.array().length) {
                bytes = buffer.array();
            } else {
                bytes = new byte[buffer.readableBytes()];
                buffer.readBytes(bytes);
            }
            future.complete(valueSerde.fromBytes(bytes));
        } catch (Exception e) {
            future.completeExceptionally(new SamzaException(
                    String.format("Failed to deserialize value of key %s with given serde", key), e));
        } finally {
            ReferenceCountUtil.release(buffer);
        }
    }
}