contrib/src/main/java/org/apache/apex/malhar/contrib/elasticsearch/AbstractElasticSearchInputOperator.java

/**
 * 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 com.datatorrent.contrib.elasticsearch;

import org.elasticsearch.action.search.SearchRequestBuilder;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.search.SearchHit;

import com.datatorrent.api.Context.OperatorContext;
import com.datatorrent.lib.db.AbstractStoreInputOperator;

/**
 * This is the base implementation for a non transactional input operator for ElasticSearch
 * <br>
 * Ports:<br>
 * <b>Input</b>: no input port<br>
 * <b>Output</b>: You can have one output port<br>
 * <br>
 * Compile time checks:<br>
 * None<br>
 * <br>
 * Run time checks:<br>
 * hostName port<br>
 *
 * <b>Benchmarks</b>: <br>
 *
 * @displayName Elastic Search Input
 * @category Input
 * @tags elastic search
 *
 * @since 2.1.0
 */
public abstract class AbstractElasticSearchInputOperator<T, S extends ElasticSearchConnectable> extends AbstractStoreInputOperator<T, S>
{
  protected transient SearchRequestBuilder searchRequestBuilder;

  /**
   * Initializing transient fields such as ElasticSearchConnectable, SearchRequestBuilder
   *
   * @see com.datatorrent.lib.db.AbstractStoreInputOperator#setup(com.datatorrent.api.Context.OperatorContext)
   */
  @Override
  public void setup(OperatorContext t1)
  {
    super.setup(t1);
    this.searchRequestBuilder = new SearchRequestBuilder(store.client);
  }

  /**
   * Emit one tuple per {@code SearchHit} for given search query
   *
   * @see com.datatorrent.api.InputOperator#emitTuples()
   */
  @Override
  public void emitTuples()
  {
    SearchResponse response = getSearchRequestBuilder().execute().actionGet();
    for (SearchHit hit : response.getHits().hits()) {
      T tuple = convertToTuple(hit);
      if (tuple != null) {
        outputPort.emit(tuple);
      }
    }
  }

  /**
   * Converts SearchHit to Tuple
   *
   * @param hit
   * @return tuple constructed from <code>hit</code>
   */
  protected abstract T convertToTuple(SearchHit hit);

  /**
   * Set {@link SearchRequestBuilder} properties according to search query requirements. Properties which do not change
   * for each window can be set in {@code setup()}. Properties which may change for each window should be set in this
   * function
   *
   * @return {@link SearchRequestBuilder}
   */
  protected abstract SearchRequestBuilder getSearchRequestBuilder();

}