ElasticsearchDocumentHistory.java

//Dstl (c) Crown Copyright 2017
package uk.gov.dstl.baleen.history.elasticsearch;

import java.util.Collection;
import java.util.Collections;
import java.util.concurrent.BlockingDeque;
import java.util.concurrent.LinkedBlockingDeque;

import uk.gov.dstl.baleen.core.history.HistoryEvent;
import uk.gov.dstl.baleen.history.helpers.AbstractDocumentHistory;

/** A document history for ElasticSearch.
 *
 * This is an in-memory implementation. When a document history is requested from
 * {@link ElasticsearchHistory} the entire history is loaded into memory
 * (and not kept synchronised with ES). Events are added or the history
 * queried and saved back to ES on close.
 *
 * Thus the get events here act on memory and can be considered quick (i.e.
 * don't require a round trip to the server).
 *
 * 
 *
 */
public class ElasticsearchDocumentHistory extends AbstractDocumentHistory<ElasticsearchHistory> {

	private BlockingDeque<HistoryEvent> events;

	/** New instance, with an empty history.
	 * @param history the elasticsearch owning this history
	 * @param documentId the document id
	 */
	public ElasticsearchDocumentHistory(ElasticsearchHistory history, String documentId) {
		this(history, documentId, new LinkedBlockingDeque<HistoryEvent>());
	}

	/** New instance, with an existing history.
	 * @param history the elasticsearch owning this history
	 * @param documentId the document id
	 * @param events the events to populate the history with. This class assumes ownership (and will likely modify)
	 */
	public ElasticsearchDocumentHistory(ElasticsearchHistory history, String documentId,
			BlockingDeque<HistoryEvent> events) {
		super(history, documentId);
		this.events = events != null ? events : new LinkedBlockingDeque<HistoryEvent>();
	}

	@Override
	public void add(HistoryEvent event) {
		events.add(event);
	}

	@Override
	public Collection<HistoryEvent> getAllHistory() {
		return Collections.unmodifiableCollection(events);
	}

}