BlackholeStoragePlugin.java

/*******************************************************************************
 * Copyright (c) 2011 The Board of Trustees of the Leland Stanford Junior University
 * as Operator of the SLAC National Accelerator Laboratory.
 * Copyright (c) 2011 Brookhaven National Laboratory.
 * EPICS archiver appliance is distributed subject to a Software License Agreement found
 * in file LICENSE that is included with this distribution.
 *******************************************************************************/
package org.epics.archiverappliance.utils.blackhole;

import java.io.IOException;
import java.io.StringWriter;
import java.io.UnsupportedEncodingException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URLEncoder;
import java.sql.Timestamp;
import java.util.HashMap;
import java.util.List;
import java.util.concurrent.Callable;

import org.apache.log4j.Logger;
import org.epics.archiverappliance.Event;
import org.epics.archiverappliance.EventStream;
import org.epics.archiverappliance.StoragePlugin;
import org.epics.archiverappliance.common.BasicContext;
import org.epics.archiverappliance.common.PartitionGranularity;
import org.epics.archiverappliance.config.ArchDBRTypes;
import org.epics.archiverappliance.config.ConfigService;
import org.epics.archiverappliance.etl.ConversionFunction;
import org.epics.archiverappliance.etl.ETLContext;
import org.epics.archiverappliance.etl.ETLDest;
import org.epics.archiverappliance.retrieval.postprocessors.PostProcessor;
import org.epics.archiverappliance.utils.ui.URIUtils;

/**
 * A storage plugin that deletes all data that goes into it.
 * Use this as an ETL dest for policies that eliminate data after a certain period.
 * @author mshankar
 *
 */
public class BlackholeStoragePlugin implements StoragePlugin, ETLDest {
	private static Logger logger = Logger.getLogger(BlackholeStoragePlugin.class.getName());

	@Override
	public List<Callable<EventStream>> getDataForPV(BasicContext context, String pvName, Timestamp startTime, Timestamp endTime, PostProcessor postProcessor)  throws IOException {
		// A blackhole plugin has no data
		return null;
	}

	@Override
	public boolean appendData(BasicContext context, String pvName, EventStream stream) {
		return true;
	}

	@Override
	public Event getLastKnownEvent(BasicContext context, String pvName) throws IOException {
		// A blackhole plugin has no data
		return null;
	}
	
	@Override
	public Event getFirstKnownEvent(BasicContext context, String pvName) throws IOException {
		return null;
	}

	@Override
	public boolean prepareForNewPartition(String pvName, Event ev, ArchDBRTypes archDBRType, ETLContext context) throws IOException {
		return true;
	}

	@Override
	public boolean appendToETLAppendData(String pvName, EventStream stream, ETLContext context) {
		return true;
	}

	@Override
	public boolean commitETLAppendData(String pvName, ETLContext context) throws IOException {
		return true;
	}
	
	@Override
	public boolean runPostProcessors(String pvName, ArchDBRTypes dbrtype, ETLContext context) throws IOException {
		return true;
	}

	@Override
	public PartitionGranularity getPartitionGranularity() {
		return PartitionGranularity.PARTITION_YEAR;
	}

	@Override
	public String getDescription() {
		return "A black hole plugin";
	}
	
	public String getURLRepresentation() {
		StringWriter ret = new StringWriter();
		ret.append("blackhole://localhost");
		try { 
			ret.append("?name=");
			ret.append(URLEncoder.encode(name, "UTF-8"));
		} catch(UnsupportedEncodingException ex) { }
		
		return ret.toString();
	}

	private String name = "blackhole";
	@Override
	public void initialize(String configURL, ConfigService configService) throws IOException {
		try { 
			URI srcURI = new URI(configURL);
			HashMap<String, String> queryNVPairs = URIUtils.parseQueryString(srcURI);

			if(queryNVPairs.containsKey("name")) {
				name = queryNVPairs.get("name");
			} else {
				logger.debug("Using the default name of " + name + " for this blackhole engine");
			}
		} catch(URISyntaxException ex) {
			throw new IOException(ex);
		}
	}

	@Override
	public String getName() {
		return name;
	}

	@Override
	public void renamePV(BasicContext context, String oldName, String newName) throws IOException {
		// Nothing to do here.
	}

	@Override
	public void convert(BasicContext context, String pvName, ConversionFunction conversionFuntion) throws IOException {
		// Nothing to do here.
	}
}