org.apache.beam.runners.dataflow.worker.ReaderRegistry.java Source code

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Here is the source code for org.apache.beam.runners.dataflow.worker.ReaderRegistry.java

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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.beam.runners.dataflow.worker;

import com.google.api.services.dataflow.model.Source;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.collect.Sets;
import java.util.HashMap;
import java.util.Map;
import java.util.ServiceLoader;
import java.util.Set;
import javax.annotation.Nullable;
import org.apache.beam.runners.dataflow.util.CloudObject;
import org.apache.beam.runners.dataflow.util.CloudObjects;
import org.apache.beam.runners.dataflow.worker.util.CloudSourceUtils;
import org.apache.beam.runners.dataflow.worker.util.common.worker.NativeReader;
import org.apache.beam.sdk.coders.Coder;
import org.apache.beam.sdk.options.PipelineOptions;
import org.apache.beam.sdk.util.common.ReflectHelpers;

/**
 * An immutable registry from {@link String} identifiers (provided to the worker by the Dataflow
 * service) to appropriate {@link ReaderFactory} instances.
 */
public class ReaderRegistry implements ReaderFactory {

    /**
     * A {@link ReaderRegistry} with each {@link ReaderFactory} known to the Dataflow worker already
     * registered.
     *
     * <p>Uses {@link ServiceLoader} to dynamically bind well known types to reader factories via a
     * {@link ReaderFactory.Registrar}.
     */
    public static ReaderRegistry defaultRegistry() {
        Set<ReaderFactory.Registrar> readerFactoryRegistrars = Sets
                .newTreeSet(ReflectHelpers.ObjectsClassComparator.INSTANCE);
        readerFactoryRegistrars.addAll(Lists
                .newArrayList(ServiceLoader.load(ReaderFactory.Registrar.class, ReflectHelpers.findClassLoader())));

        ImmutableMap.Builder<String, ReaderFactory> factories = ImmutableMap.builder();
        for (ReaderFactory.Registrar registrar : readerFactoryRegistrars) {
            factories.putAll(registrar.factories());
        }
        return new ReaderRegistry(factories.build());
    }

    /** Builds a new {@link ReaderRegistry} with the provided mappings. */
    private ReaderRegistry(Map<String, ReaderFactory> factories) {
        // ConcatReader requires special treatment: Recursive access to the registry since it calls
        // back to create its sub-readers lazily.
        this.factories = new HashMap<>(factories);
        this.factories.put(ConcatReader.SOURCE_NAME, ConcatReaderFactory.withRegistry(this));
    }

    /** A map from the short names of predefined sources to the associated {@link ReaderFactory}. */
    private final Map<String, ReaderFactory> factories;

    /**
     * Returns a new {@link ReaderRegistry} with the provided identifier associated with the provided
     * {@link ReaderFactory}, overriding any existing binding for that identifier.
     */
    public ReaderRegistry register(String readerSpecType, ReaderFactory factory) {
        Map<String, ReaderFactory> newFactories = Maps.newHashMap();
        newFactories.putAll(factories);
        newFactories.put(readerSpecType, factory);
        return new ReaderRegistry(newFactories);
    }

    /**
     * Creates a {@link NativeReader} according to the provided {@code sourceSpec}, by dispatching on
     * the type of {@link CloudObject} to instantiate.
     */
    @Override
    public NativeReader<?> create(CloudObject sourceSpec, @Nullable Coder<?> coder,
            @Nullable PipelineOptions options, @Nullable DataflowExecutionContext executionContext,
            DataflowOperationContext operationContext) throws Exception {

        ReaderFactory readerFactory = factories.get(sourceSpec.getClassName());
        if (readerFactory == null) {
            throw new IllegalArgumentException(
                    String.format("Unable to create a Reader: Unknown Reader type in Source specification: %s",
                            sourceSpec.getClassName()));
        }
        return readerFactory.create(sourceSpec, coder, options, executionContext, operationContext);
    }

    /**
     * Creates a {@link NativeReader} from a Dataflow API {@link Source} specification, using the
     * {@link Coder} contained in the {@link Source} specification.
     */
    public NativeReader<?> create(Source cloudSource, @Nullable PipelineOptions options,
            @Nullable DataflowExecutionContext executionContext, DataflowOperationContext operationContext)
            throws Exception {

        cloudSource = CloudSourceUtils.flattenBaseSpecs(cloudSource);
        CloudObject sourceSpec = CloudObject.fromSpec(cloudSource.getSpec());
        Coder<?> coder = null;
        if (cloudSource.getCodec() != null) {
            coder = CloudObjects.coderFromCloudObject(CloudObject.fromSpec(cloudSource.getCodec()));
        }
        return create(sourceSpec, coder, options, executionContext, operationContext);
    }
}