Java tutorial
/* * Copyright (c) 2010 TransPac Software, Inc. * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. * */ package bixo.examples; import java.util.HashMap; import java.util.Iterator; import java.util.Map; import org.apache.hadoop.fs.FileSystem; import org.apache.hadoop.fs.Path; import org.apache.hadoop.mapred.JobConf; import org.apache.log4j.Logger; import bixo.cascading.NullContext; import bixo.config.FetcherPolicy; import bixo.config.UserAgent; import bixo.datum.FetchedDatum; import bixo.datum.ParsedDatum; import bixo.datum.UrlDatum; import bixo.fetcher.BaseFetcher; import bixo.fetcher.SimpleHttpFetcher; import bixo.hadoop.HadoopUtils; import bixo.operations.BaseScoreGenerator; import bixo.operations.FixedScoreGenerator; import bixo.operations.NormalizeUrlFunction; import bixo.operations.UrlFilter; import bixo.parser.SimpleParser; import bixo.pipes.FetchPipe; import bixo.pipes.ParsePipe; import bixo.urls.BaseUrlFilter; import bixo.urls.SimpleUrlNormalizer; import cascading.flow.Flow; import cascading.flow.FlowConnector; import cascading.flow.FlowProcess; import cascading.operation.BaseOperation; import cascading.operation.Buffer; import cascading.operation.BufferCall; import cascading.operation.OperationCall; import cascading.pipe.Each; import cascading.pipe.Every; import cascading.pipe.GroupBy; import cascading.pipe.Pipe; import cascading.scheme.SequenceFile; import cascading.scheme.TextLine; import cascading.tap.Hfs; import cascading.tap.Tap; import cascading.tuple.Fields; import cascading.tuple.TupleEntry; public class JDBCCrawlWorkflow { private static final Logger LOGGER = Logger.getLogger(JDBCCrawlWorkflow.class); @SuppressWarnings("serial") private static class BestUrlToFetchBuffer extends BaseOperation<NullContext> implements Buffer<NullContext> { private long _numSelected = 0; public BestUrlToFetchBuffer() { super(UrlDatum.FIELDS); } @Override public void prepare(FlowProcess process, OperationCall<NullContext> operationCall) { LOGGER.info("Starting selection of best URLs to fetch"); } @Override public void cleanup(FlowProcess process, OperationCall<NullContext> operationCall) { LOGGER.info("Ending selection of best URLs to fetch - selected " + _numSelected + " urls"); } @Override public void operate(FlowProcess process, BufferCall<NullContext> bufferCall) { CrawlDbDatum bestDatum = null; Iterator<TupleEntry> iter = bufferCall.getArgumentsIterator(); while (iter.hasNext()) { CrawlDbDatum datum = new CrawlDbDatum(iter.next()); if (bestDatum == null) { bestDatum = datum; } else if (datum.getLastFetched() > bestDatum.getLastFetched()) { bestDatum = datum; } } if (bestDatum != null && bestDatum.getLastFetched() == 0) { UrlDatum urlDatum = new UrlDatum(bestDatum.getUrl()); urlDatum.setPayloadValue(CrawlDbDatum.LAST_FETCHED_FIELD, bestDatum.getLastFetched()); urlDatum.setPayloadValue(CrawlDbDatum.LAST_UPDATED_FIELD, bestDatum.getLastUpdated()); urlDatum.setPayloadValue(CrawlDbDatum.LAST_STATUS_FIELD, bestDatum.getLastStatus().name()); urlDatum.setPayloadValue(CrawlDbDatum.CRAWL_DEPTH, bestDatum.getCrawlDepth()); bufferCall.getOutputCollector().add(urlDatum.getTuple()); _numSelected++; } } } public static Flow createFlow(Path inputDir, Path curLoopDirPath, UserAgent userAgent, FetcherPolicy fetcherPolicy, BaseUrlFilter urlFilter, int maxThreads, boolean debug, String persistentDbLocation) throws Throwable { JobConf conf = HadoopUtils.getDefaultJobConf(CrawlConfig.CRAWL_STACKSIZE_KB); int numReducers = conf.getNumReduceTasks() * HadoopUtils.getTaskTrackers(conf); FileSystem fs = curLoopDirPath.getFileSystem(conf); if (!fs.exists(inputDir)) { throw new IllegalStateException(String.format("Input directory %s doesn't exist", inputDir)); } Tap inputSource = JDBCTapFactory.createUrlsSourceJDBCTap(persistentDbLocation); // Read _everything_ in initially // Split that pipe into URLs we want to fetch for the fetch pipe Pipe importPipe = new Pipe("url importer"); importPipe = new GroupBy(importPipe, new Fields(CrawlDbDatum.URL_FIELD)); importPipe = new Every(importPipe, new BestUrlToFetchBuffer(), Fields.RESULTS); Path contentPath = new Path(curLoopDirPath, CrawlConfig.CRAWLDB_SUBDIR_NAME); Tap contentSink = new Hfs(new SequenceFile(FetchedDatum.FIELDS), contentPath.toString()); Path parsePath = new Path(curLoopDirPath, CrawlConfig.PARSE_SUBDIR_NAME); Tap parseSink = new Hfs(new SequenceFile(ParsedDatum.FIELDS), parsePath.toString()); Path statusDirPath = new Path(curLoopDirPath, CrawlConfig.STATUS_SUBDIR_NAME); Tap statusSink = new Hfs(new TextLine(), statusDirPath.toString()); // NOTE: The source and sink for CrawlDbDatums is essentially the same database - // since cascading doesn't allow you to use the same tap for source and // sink we fake it by creating two separate taps. Tap urlSink = JDBCTapFactory.createUrlsSinkJDBCTap(persistentDbLocation); // Create the sub-assembly that runs the fetch job BaseFetcher fetcher = new SimpleHttpFetcher(maxThreads, fetcherPolicy, userAgent); BaseScoreGenerator scorer = new FixedScoreGenerator(); FetchPipe fetchPipe = new FetchPipe(importPipe, scorer, fetcher, numReducers); Pipe statusPipe = new Pipe("status pipe", fetchPipe.getStatusTailPipe()); // Take content and split it into content output plus parse to extract URLs. ParsePipe parsePipe = new ParsePipe(fetchPipe.getContentTailPipe(), new SimpleParser()); Pipe urlFromOutlinksPipe = new Pipe("url from outlinks", parsePipe.getTailPipe()); urlFromOutlinksPipe = new Each(urlFromOutlinksPipe, new CreateUrlDatumFromOutlinksFunction()); urlFromOutlinksPipe = new Each(urlFromOutlinksPipe, new UrlFilter(urlFilter)); urlFromOutlinksPipe = new Each(urlFromOutlinksPipe, new NormalizeUrlFunction(new SimpleUrlNormalizer())); // Take status and output updated UrlDatum's. Again, since we are using // the same database we need to create a new tap. Pipe urlFromFetchPipe = new Pipe("url from fetch", fetchPipe.getStatusTailPipe()); urlFromFetchPipe = new Each(urlFromFetchPipe, new CreateUrlDatumFromStatusFunction()); // Now we need to join the URLs we get from parsing content with the // URLs we got from the status output, so we have a unified stream // of all known URLs. Pipe urlPipe = new GroupBy("url pipe", Pipe.pipes(urlFromFetchPipe, urlFromOutlinksPipe), new Fields(UrlDatum.URL_FN)); urlPipe = new Every(urlPipe, new LatestUrlDatumBuffer(), Fields.RESULTS); Pipe outputPipe = new Pipe("output pipe"); outputPipe = new Each(urlPipe, new CreateCrawlDbDatumFromUrlFunction()); // Create the output map that connects each tail pipe to the appropriate sink. Map<String, Tap> sinkMap = new HashMap<String, Tap>(); sinkMap.put(statusPipe.getName(), statusSink); sinkMap.put(FetchPipe.CONTENT_PIPE_NAME, contentSink); sinkMap.put(ParsePipe.PARSE_PIPE_NAME, parseSink); sinkMap.put(outputPipe.getName(), urlSink); // Finally we can run it. FlowConnector flowConnector = new FlowConnector( HadoopUtils.getDefaultProperties(JDBCCrawlWorkflow.class, debug, conf)); return flowConnector.connect(inputSource, sinkMap, statusPipe, fetchPipe.getContentTailPipe(), parsePipe.getTailPipe(), outputPipe); } }