DiffEventProducer.java

/*
 * Copyright 2012-2015, the original author or authors.
 *
 * Licensed 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.flipkart.aesop.runtime.producer.diff;

import org.apache.avro.generic.GenericRecord;
import org.springframework.util.Assert;

import com.flipkart.aesop.runtime.producer.AbstractCallbackEventProducer;
import com.flipkart.aesop.runtime.producer.AbstractEventProducer;
import com.flipkart.aesop.runtime.producer.ReadEventCycleSummary;
import com.flipkart.aesop.serializer.stateengine.DiffInterpreter;
import com.linkedin.databus2.producers.EventCreationException;
import com.netflix.zeno.fastblob.FastBlobStateEngine;

/**
 * <code>DiffEventProducer</code> is a sub-type of {@link AbstractEventProducer} that interprets change events by loading snapshots and deltas onto a 
 * Zeno {@link FastBlobStateEngine} instance and listening in on the state change.
 * This class 
 *
 * @author Regunath B
 * @version 1.0, 17 March 2014
 */
public class DiffEventProducer <T, S extends GenericRecord> extends AbstractCallbackEventProducer<S> {

	/** The DiffInterpreter used for loading state engine snapshots and deltas and listening-in on the engine's state change*/
	private DiffInterpreter<T,S> diffInterpreter;

	/**
	 * Overriden superclass method. Calls {@link AbstractCallbackEventProducer#afterPropertiesSet()} and then checks for mandatory dependencies for this producer
	 * @see com.flipkart.aesop.runtime.producer.AbstractCallbackEventProducer#afterPropertiesSet()
	 */
	public void afterPropertiesSet() throws Exception {
		super.afterPropertiesSet();
		Assert.notNull(this.diffInterpreter,"'diffInterpreter' cannot be null. No state engine serialized state diff interpreter found. This Diff Events producer will not be initialized");		
	}

	/**
	 * Abstract method implementation. Loads serialized snapshots and deltas from the specified SCN and interprets change events by listening in on the state engine
	 * changes.
	 * @see com.flipkart.aesop.runtime.producer.AbstractCallbackEventProducer#readEventsFromAllSources(long)
	 */
	protected ReadEventCycleSummary<S> readEventsFromAllSources(long sinceSCN) throws EventCreationException {
		return this.diffInterpreter.getChangeEvents(sinceSCN);
	}
	
	/**
	 * Abstract method implementation. Delegates the call to DiffChangeEventMapper
	 * @see com.flipkart.aesop.runtime.producer.AbstractCallbackEventProducer#getEventKey(org.apache.avro.generic.GenericRecord)
	 */
	protected Object getEventKey(S changeEvent) {
		return this.diffInterpreter.getDiffChangeEventMapper().getChangeEventKey(changeEvent);
	}
	
	/**
	 * Abstract method implementation. Delegates the call to DiffChangeEventMapper
	 * @see com.flipkart.aesop.runtime.producer.AbstractCallbackEventProducer#getSequenceId(org.apache.avro.generic.GenericRecord)
	 */
	protected Long getSequenceId(S changeEvent) {
		return this.diffInterpreter.getDiffChangeEventMapper().getSequenceId(changeEvent);
	}
	
	/** Start Setter/Getter methods*/
	public void setDiffInterpreter(DiffInterpreter<T,S> diffInterpreter) {
		this.diffInterpreter = diffInterpreter;
	}
	/** End Setter/Getter methods*/

}