io.druid.server.namespace.KafkaExtractionNamespaceFactory.java Source code

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Here is the source code for io.druid.server.namespace.KafkaExtractionNamespaceFactory.java

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/*
 * Licensed to Metamarkets Group Inc. (Metamarkets) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  Metamarkets 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 io.druid.server.namespace;

import com.google.common.base.Function;
import com.google.common.base.Strings;
import com.google.inject.Inject;
import io.druid.query.extraction.namespace.ExtractionNamespaceFunctionFactory;
import io.druid.query.extraction.namespace.KafkaExtractionNamespace;

import javax.annotation.Nullable;
import java.util.Map;
import java.util.concurrent.Callable;

/**
 *
 */
public class KafkaExtractionNamespaceFactory
        implements ExtractionNamespaceFunctionFactory<KafkaExtractionNamespace> {
    private final KafkaExtractionManager kafkaExtractionManager;
    private static final String KAFKA_VERSION = "kafka versions are updated every time a new event comes in";

    @Inject
    public KafkaExtractionNamespaceFactory(final KafkaExtractionManager kafkaExtractionManager) {
        this.kafkaExtractionManager = kafkaExtractionManager;
    }

    @Override
    public Function<String, String> build(KafkaExtractionNamespace extractionNamespace,
            final Map<String, String> cache) {
        return new Function<String, String>() {
            @Nullable
            @Override
            public String apply(String input) {
                if (Strings.isNullOrEmpty(input)) {
                    return null;
                }
                return Strings.emptyToNull(cache.get(input));
            }
        };
    }

    // This only fires ONCE when the namespace is first added. The version is updated externally as events come in
    @Override
    public Callable<String> getCachePopulator(final KafkaExtractionNamespace extractionNamespace,
            final String unused, final Map<String, String> cache) {
        return new Callable<String>() {
            @Override
            public String call() {
                kafkaExtractionManager.addListener(extractionNamespace, cache);
                return KAFKA_VERSION;
            }
        };
    }
}