private static class QueueFeeder extends Thread {
private RecordReader<Text, CrawlDatum> reader;
private FetchItemQueues queues; //生产者和消费者的共享序列，分层，一层对应一个host
private int size;
private long timelimit = -1;
public QueueFeeder(RecordReader<Text, CrawlDatum> reader,
FetchItemQueues queues, int size) {
this.reader = reader;
this.queues = queues;
this.size = size;
this.setDaemon(true);
this.setName("QueueFeeder");
}
public void setTimeLimit(long tl) {
timelimit = tl;
}
public void run() {
boolean hasMore = true;
int cnt = 0;
int timelimitcount = 0;
while (hasMore) {
// 这里判断是否设置了这个过滤机制，如果设置了，判断相前时间是否大于这个timelimit，如果大于timelimit，过滤所有的FetchItem
if (System.currentTimeMillis() >= timelimit && timelimit != -1) {
// enough .. lets' simply
// read all the entries from the input without processing them
try {
Text url = new Text();
CrawlDatum datum = new CrawlDatum();
hasMore = reader.next(url, datum);
timelimitcount++;
} catch (IOException e) {
LOG.error("QueueFeeder error reading input, record " + cnt, e);
return;
}
continue;
}
int feed = size - queues.getTotalSize();
if (feed <= 0) {
// queues are full - spin-wait until they have some free space
try {
Thread.sleep(1000);
} catch (Exception e) {};
continue;
} else {
LOG.debug("-feeding " + feed + " input urls ...");
while (feed > 0 && hasMore) {
try {
Text url = new Text();
CrawlDatum datum = new CrawlDatum();
hasMore = reader.next(url, datum);
if (hasMore) {
queues.addFetchItem(url, datum);
cnt++; // 统计总数
feed--; // 剩余队列空间减1
}
} catch (IOException e) {
LOG.error("QueueFeeder error reading input, record " + cnt, e);
return;
}
}
}
}
LOG.info("QueueFeeder finished: total " + cnt + " records + hit by time limit :"
+ timelimitcount);
}
}
这个类主要负责向队列中放数据。
public void run() {
activeThreads.incrementAndGet(); // count threads
FetchItem fit = null;
try {
while (true) {
fit = fetchQueues.getFetchItem();
if (fit == null) {
//如果生产者还存活，或者队列里还有数据，等待
if (feeder.isAlive() || fetchQueues.getTotalSize() > 0) {
LOG.debug(getName() + " spin-waiting ...");
// spin-wait.
spinWaiting.incrementAndGet();
try {
Thread.sleep(500);
} catch (Exception e) {}
spinWaiting.decrementAndGet();
continue;
} else {
//认为已经处理完，结束
// all done, finish this thread
return;
}
}
lastRequestStart.set(System.currentTimeMillis());
//获得url
Text reprUrlWritable =
(Text) fit.datum.getMetaData().get(Nutch.WRITABLE_REPR_URL_KEY);
if (reprUrlWritable == null) {
reprUrl = fit.url.toString();
} else {
reprUrl = reprUrlWritable.toString();
}
try {
// fetch the page
redirecting = false;
redirectCount = 0;
do {
if (LOG.isInfoEnabled()) { LOG.info("fetching " + fit.url); }
if (LOG.isDebugEnabled()) {
LOG.debug("redirectCount=" + redirectCount);
}
redirecting = false;
//从这个url中分析出所使用的协议
Protocol protocol = this.protocolFactory.getProtocol(fit.url.toString());
//根据对应的协议处理
RobotRules rules = protocol.getRobotRules(fit.url, fit.datum);
//不符合规则，过滤掉
if (!rules.isAllowed(fit.u)) {
// unblock
fetchQueues.finishFetchItem(fit, true);
if (LOG.isDebugEnabled()) {
LOG.debug("Denied by robots.txt: " + fit.url);
}
output(fit.url, fit.datum, null, ProtocolStatus.STATUS_ROBOTS_DENIED, CrawlDatum.STATUS_FETCH_GONE);
reporter.incrCounter("FetcherStatus", "robots_denied", 1);
continue;
}
//如果delayTime>maxCrawlDelay 过滤掉
if (rules.getCrawlDelay() > 0) {
if (rules.getCrawlDelay() > maxCrawlDelay) {
// unblock
fetchQueues.finishFetchItem(fit, true);
LOG.debug("Crawl-Delay for " + fit.url + " too long (" + rules.getCrawlDelay() + "), skipping");
output(fit.url, fit.datum, null, ProtocolStatus.STATUS_ROBOTS_DENIED, CrawlDatum.STATUS_FETCH_GONE);
reporter.incrCounter("FetcherStatus", "robots_denied_maxcrawldelay", 1);
continue;
} else {
FetchItemQueue fiq = fetchQueues.getFetchItemQueue(fit.queueID);
fiq.crawlDelay = rules.getCrawlDelay();
}
}
//进行抓取
ProtocolOutput output = protocol.getProtocolOutput(fit.url, fit.datum);
//抓取状态
ProtocolStatus status = output.getStatus();
//抓取内容
Content content = output.getContent();
ParseStatus pstatus = null;
// unblock queue
fetchQueues.finishFetchItem(fit);
String urlString = fit.url.toString();
//计数
reporter.incrCounter("FetcherStatus", status.getName(), 1);
//根据状态执行
// 如果状态为WOULDBLOCK，那就进行retry,把当前url放加FetchItemQueues中，进行重试
// 如果是MOVED或者TEMP_MOVED,这时这个网页可以被重定向了，对其重定向的内容进行解析，得到重定向的网址，这时要生成一个新的FetchItem，根据其QueueID放到相应的队列的inProgress集合中，然后再对这个重定向的网页进行抓取
// 如果状态是EXCEPTION,对当前url所属的FetchItemQueue进行检测，看其异常的网页数有没有超过最大异常网页数，如果大于，那就清空这个队列，认为这个队列中的所有网页都有问题。
// 如果状态是RETRY或者是BLOCKED，那就输出CrawlDatum，将其状态设置成STATUS_FETCH_RETRY,在下一轮进行重新抓取
// 如果状态是GONE,NOTFOUND,ACCESS_DENIED,ROBOTS_DENIED，那就输出CrawlDatum，设置其状态为STATUS_FETCH_GONE，可能在下一轮中就不进行抓取了，
// 如果状态是NOTMODIFIED，那就认为这个网页没有改变过，那就输出其CrawlDatum，将其状态设成成STATUS_FETCH_NOTMODIFIED.
// 如果所有状态都没有找到，那默认输出其CrawlDatum,将其状态设置成STATUS_FETCH_RETRY，在下一轮抓取中再重试
switch(status.getCode()) {
case ProtocolStatus.WOULDBLOCK:
// retry ?
// 重试
fetchQueues.addFetchItem(fit);
break;
case ProtocolStatus.SUCCESS: // got a page
//获得页面
pstatus = output(fit.url, fit.datum, content, status, CrawlDatum.STATUS_FETCH_SUCCESS, fit.outlinkDepth);
updateStatus(content.getContent().length);
//如果是ParseStatus.SUCCESS_REDIRECT
if (pstatus != null && pstatus.isSuccess() &&
pstatus.getMinorCode() == ParseStatus.SUCCESS_REDIRECT) {
//获得跳转url
String newUrl = pstatus.getMessage();
int refreshTime = Integer.valueOf(pstatus.getArgs()[1]);
//跳转
Text redirUrl =
handleRedirect(fit.url, fit.datum,
urlString, newUrl,
refreshTime < Fetcher.PERM_REFRESH_TIME,
Fetcher.CONTENT_REDIR);
//获得内容不为空
if (redirUrl != null) {
//生成对应的CrawlDatum
CrawlDatum newDatum = new CrawlDatum(CrawlDatum.STATUS_DB_UNFETCHED,
fit.datum.getFetchInterval(), fit.datum.getScore());
// transfer existing metadata to the redir
newDatum.getMetaData().putAll(fit.datum.getMetaData());
scfilters.initialScore(redirUrl, newDatum);
if (reprUrl != null) {
newDatum.getMetaData().put(Nutch.WRITABLE_REPR_URL_KEY,
new Text(reprUrl));
}
//生成对应的FetchItem
fit = FetchItem.create(redirUrl, newDatum, queueMode);
if (fit != null) {
//放入队列中待抓取
FetchItemQueue fiq =
fetchQueues.getFetchItemQueue(fit.queueID);
fiq.addInProgressFetchItem(fit);
} else {
//跳转失败，计数
// stop redirecting
redirecting = false;
reporter.incrCounter("FetcherStatus", "FetchItem.notCreated.redirect", 1);
}
}
}
break;
case ProtocolStatus.MOVED: // redirect
case ProtocolStatus.TEMP_MOVED:
int code;
boolean temp;
if (status.getCode() == ProtocolStatus.MOVED) {
code = CrawlDatum.STATUS_FETCH_REDIR_PERM;
temp = false;
} else {
code = CrawlDatum.STATUS_FETCH_REDIR_TEMP;
temp = true;
}
output(fit.url, fit.datum, content, status, code);
String newUrl = status.getMessage();
Text redirUrl =
handleRedirect(fit.url, fit.datum,
urlString, newUrl, temp,
Fetcher.PROTOCOL_REDIR);
if (redirUrl != null) {
CrawlDatum newDatum = new CrawlDatum(CrawlDatum.STATUS_DB_UNFETCHED,
fit.datum.getFetchInterval(), fit.datum.getScore());
// transfer existing metadata
newDatum.getMetaData().putAll(fit.datum.getMetaData());
scfilters.initialScore(redirUrl, newDatum);
if (reprUrl != null) {
newDatum.getMetaData().put(Nutch.WRITABLE_REPR_URL_KEY,
new Text(reprUrl));
}
fit = FetchItem.create(redirUrl, newDatum, queueMode);
if (fit != null) {
FetchItemQueue fiq =
fetchQueues.getFetchItemQueue(fit.queueID);
fiq.addInProgressFetchItem(fit);
} else {
// stop redirecting
redirecting = false;
reporter.incrCounter("FetcherStatus", "FetchItem.notCreated.redirect", 1);
}
} else {
// stop redirecting
redirecting = false;
}
break;
case ProtocolStatus.EXCEPTION:
logError(fit.url, status.getMessage());
int killedURLs = fetchQueues.checkExceptionThreshold(fit.getQueueID());
if (killedURLs!=0)
reporter.incrCounter("FetcherStatus", "AboveExceptionThresholdInQueue", killedURLs);
/* FALLTHROUGH */
case ProtocolStatus.RETRY: // retry
case ProtocolStatus.BLOCKED:
output(fit.url, fit.datum, null, status, CrawlDatum.STATUS_FETCH_RETRY);
break;
case ProtocolStatus.GONE: // gone
case ProtocolStatus.NOTFOUND:
case ProtocolStatus.ACCESS_DENIED:
case ProtocolStatus.ROBOTS_DENIED:
output(fit.url, fit.datum, null, status, CrawlDatum.STATUS_FETCH_GONE);
break;
case ProtocolStatus.NOTMODIFIED:
output(fit.url, fit.datum, null, status, CrawlDatum.STATUS_FETCH_NOTMODIFIED);
break;
default:
if (LOG.isWarnEnabled()) {
LOG.warn("Unknown ProtocolStatus: " + status.getCode());
}
output(fit.url, fit.datum, null, status, CrawlDatum.STATUS_FETCH_RETRY);
}
if (redirecting && redirectCount > maxRedirect) {
fetchQueues.finishFetchItem(fit);
if (LOG.isInfoEnabled()) {
LOG.info(" - redirect count exceeded " + fit.url);
}
output(fit.url, fit.datum, null, ProtocolStatus.STATUS_REDIR_EXCEEDED, CrawlDatum.STATUS_FETCH_GONE);
}
} while (redirecting && (redirectCount <= maxRedirect));
} catch (Throwable t) { // unexpected exception
// unblock
fetchQueues.finishFetchItem(fit);
logError(fit.url, StringUtils.stringifyException(t));
output(fit.url, fit.datum, null, ProtocolStatus.STATUS_FAILED, CrawlDatum.STATUS_FETCH_RETRY);
}
}
} catch (Throwable e) {
if (LOG.isErrorEnabled()) {
LOG.error("fetcher caught:"+e.toString());
}
} finally {
if (fit != null) fetchQueues.finishFetchItem(fit);
activeThreads.decrementAndGet(); // count threads
LOG.info("-finishing thread " + getName() + ", activeThreads=" + activeThreads);
}
}
private ParseStatus output(Text key, CrawlDatum datum,
Content content, ProtocolStatus pstatus, int status, int outlinkDepth) {
//封装CrawlDatum
datum.setStatus(status);
datum.setFetchTime(System.currentTimeMillis());
if (pstatus != null) datum.getMetaData().put(Nutch.WRITABLE_PROTO_STATUS_KEY, pstatus);
ParseResult parseResult = null;
if (content != null) {
Metadata metadata = content.getMetadata();
//记录content type
// store the guessed content type in the crawldatum
if (content.getContentType() != null) datum.getMetaData().put(new Text(Metadata.CONTENT_TYPE), new Text(content.getContentType()));
// add segment to metadata
metadata.set(Nutch.SEGMENT_NAME_KEY, segmentName);
// add score to content metadata so that ParseSegment can pick it up.
try {
scfilters.passScoreBeforeParsing(key, datum, content);
} catch (Exception e) {
if (LOG.isWarnEnabled()) {
LOG.warn("Couldn't pass score, url " + key + " (" + e + ")");
}
}
/* Note: Fetcher will only follow meta-redirects coming from the
* original URL. */
if (parsing && status == CrawlDatum.STATUS_FETCH_SUCCESS) {
if (!skipTruncated || (skipTruncated && !ParseSegment.isTruncated(content))) {
try {
//对抓到的源码解析
parseResult = this.parseUtil.parse(content);
} catch (Exception e) {
LOG.warn("Error parsing: " + key + ": " + StringUtils.stringifyException(e));
}
}
if (parseResult == null) {
byte[] signature =
SignatureFactory.getSignature(getConf()).calculate(content,
new ParseStatus().getEmptyParse(conf));
datum.setSignature(signature);
}
}
/* Store status code in content So we can read this value during
* parsing (as a separate job) and decide to parse or not.
*/
content.getMetadata().add(Nutch.FETCH_STATUS_KEY, Integer.toString(status));
}
try {
output.collect(key, new NutchWritable(datum));
if (content != null && storingContent)
output.collect(key, new NutchWritable(content));
if (parseResult != null) {
for (Entry<Text, Parse> entry : parseResult) {
Text url = entry.getKey();
Parse parse = entry.getValue();
ParseStatus parseStatus = parse.getData().getStatus();
ParseData parseData = parse.getData();
if (!parseStatus.isSuccess()) {
LOG.warn("Error parsing: " + key + ": " + parseStatus);
parse = parseStatus.getEmptyParse(getConf());
}
// Calculate page signature. For non-parsing fetchers this will
// be done in ParseSegment
byte[] signature =
SignatureFactory.getSignature(getConf()).calculate(content, parse);
// Ensure segment name and score are in parseData metadata
parseData.getContentMeta().set(Nutch.SEGMENT_NAME_KEY,
segmentName);
parseData.getContentMeta().set(Nutch.SIGNATURE_KEY,
StringUtil.toHexString(signature));
// Pass fetch time to content meta
parseData.getContentMeta().set(Nutch.FETCH_TIME_KEY,
Long.toString(datum.getFetchTime()));
if (url.equals(key))
datum.setSignature(signature);
try {
scfilters.passScoreAfterParsing(url, content, parse);
} catch (Exception e) {
if (LOG.isWarnEnabled()) {
LOG.warn("Couldn't pass score, url " + key + " (" + e + ")");
}
}
String fromHost;
// collect outlinks for subsequent db update
Outlink[] links = parseData.getOutlinks();
int outlinksToStore = Math.min(maxOutlinks, links.length);
if (ignoreExternalLinks) {
try {
fromHost = new URL(url.toString()).getHost().toLowerCase();
} catch (MalformedURLException e) {
fromHost = null;
}
} else {
fromHost = null;
}
int validCount = 0;
// Process all outlinks, normalize, filter and deduplicate
List<Outlink> outlinkList = new ArrayList<Outlink>(outlinksToStore);
HashSet<String> outlinks = new HashSet<String>(outlinksToStore);
for (int i = 0; i < links.length && validCount < outlinksToStore; i++) {
String toUrl = links[i].getToUrl();
toUrl = ParseOutputFormat.filterNormalize(url.toString(), toUrl, fromHost, ignoreExternalLinks, urlFilters, normalizers);
if (toUrl == null) {
continue;
}
validCount++;
links[i].setUrl(toUrl);
outlinkList.add(links[i]);
outlinks.add(toUrl);
}
// Only process depth N outlinks
if (maxOutlinkDepth > 0 && outlinkDepth < maxOutlinkDepth) {
reporter.incrCounter("FetcherOutlinks", "outlinks_detected", outlinks.size());
// Counter to limit num outlinks to follow per page
int outlinkCounter = 0;
// Calculate variable number of outlinks by depth using the divisor (outlinks = Math.floor(divisor / depth * num.links))
int maxOutlinksByDepth = (int)Math.floor(outlinksDepthDivisor / (outlinkDepth + 1) * maxOutlinkDepthNumLinks);
String followUrl;
// Walk over the outlinks and add as new FetchItem to the queues
Iterator<String> iter = outlinks.iterator();
while(iter.hasNext() && outlinkCounter < maxOutlinkDepthNumLinks) {
followUrl = iter.next();
// Check whether we'll follow external outlinks
if (outlinksIgnoreExternal) {
if (!URLUtil.getHost(url.toString()).equals(URLUtil.getHost(followUrl))) {
continue;
}
}
reporter.incrCounter("FetcherOutlinks", "outlinks_following", 1);
// Create new FetchItem with depth incremented
FetchItem fit = FetchItem.create(new Text(followUrl), new CrawlDatum(CrawlDatum.STATUS_LINKED, interval), queueMode, outlinkDepth + 1);
fetchQueues.addFetchItem(fit);
outlinkCounter++;
}
}
// Overwrite the outlinks in ParseData with the normalized and filtered set
parseData.setOutlinks((Outlink[])outlinkList.toArray(new Outlink[outlinkList.size()]));
output.collect(url, new NutchWritable(
new ParseImpl(new ParseText(parse.getText()),
parseData, parse.isCanonical())));
}
}
} catch (IOException e) {
if (LOG.isErrorEnabled()) {
LOG.error("fetcher caught:"+e.toString());
}
}
// return parse status if it exits
if (parseResult != null && !parseResult.isEmpty()) {
Parse p = parseResult.get(content.getUrl());
if (p != null) {
reporter.incrCounter("ParserStatus", ParseStatus.majorCodes[p.getData().getStatus().getMajorCode()], 1);
return p.getData().getStatus();
}
}
return null;
}
}
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