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CrawlerRetreiver.java
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CrawlerRetreiver.java
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package nu.marginalia.crawl.retreival;
import com.google.common.hash.HashFunction;
import com.google.common.hash.Hashing;
import lombok.SneakyThrows;
import nu.marginalia.crawl.retreival.fetcher.FetchResult;
import nu.marginalia.crawl.retreival.fetcher.FetchResultState;
import nu.marginalia.crawl.retreival.fetcher.HttpFetcher;
import nu.marginalia.crawling.model.spec.CrawlingSpecification;
import nu.marginalia.link_parser.LinkParser;
import nu.marginalia.crawling.model.*;
import nu.marginalia.ip_blocklist.UrlBlocklist;
import nu.marginalia.model.EdgeDomain;
import nu.marginalia.model.EdgeUrl;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.time.LocalDateTime;
import java.util.ArrayList;
import java.util.Optional;
import java.util.function.Consumer;
import java.util.function.Predicate;
import static java.lang.Math.max;
import static java.lang.Math.min;
public class CrawlerRetreiver {
private static final long DEFAULT_CRAWL_DELAY_MIN_MS = Long.getLong("defaultCrawlDelay", 1000);
private static final long DEFAULT_CRAWL_DELAY_MAX_MS = Long.getLong("defaultCrawlDelaySlow", 2500);
private static final int MAX_ERRORS = 20;
private final HttpFetcher fetcher;
/** Flag to indicate that the crawler should slow down, e.g. from 429s */
private boolean slowDown = false;
/** Testing flag to disable crawl delay (otherwise crawler tests take several minutes) */
private boolean testFlagIgnoreDelay = false;
private final String id;
private final String domain;
private final Consumer<SerializableCrawlData> crawledDomainWriter;
private static final LinkParser linkParser = new LinkParser();
private static final Logger logger = LoggerFactory.getLogger(CrawlerRetreiver.class);
private static final HashFunction hashMethod = Hashing.murmur3_128(0);
private static final UrlBlocklist urlBlocklist = new UrlBlocklist();
private static final LinkFilterSelector linkFilterSelector = new LinkFilterSelector();
private static final DomainProber domainProber = new DomainProber();
private final DomainCrawlFrontier crawlFrontier;
int errorCount = 0;
public CrawlerRetreiver(HttpFetcher fetcher, CrawlingSpecification specs, Consumer<SerializableCrawlData> writer) {
this.fetcher = fetcher;
id = specs.id;
domain = specs.domain;
crawledDomainWriter = writer;
this.crawlFrontier = new DomainCrawlFrontier(new EdgeDomain(domain), specs.urls, specs.crawlDepth);
var fst = crawlFrontier.peek();
if (fst != null) {
// Ensure the index page is always crawled
var root = fst.withPathAndParam("/", null);
if (crawlFrontier.addKnown(root))
crawlFrontier.addFirst(root);
}
else {
// We know nothing about this domain, so we'll start with the index, trying both HTTP and HTTPS
crawlFrontier.addToQueue(new EdgeUrl("http", new EdgeDomain(domain), null, "/", null));
crawlFrontier.addToQueue(new EdgeUrl("https", new EdgeDomain(domain), null, "/", null));
}
}
public CrawlerRetreiver withNoDelay() {
testFlagIgnoreDelay = true;
return this;
}
public int fetch() {
final DomainProber.ProbeResult probeResult = domainProber.probeDomain(fetcher, domain, crawlFrontier.peek());
if (probeResult instanceof DomainProber.ProbeResultOk) {
return crawlDomain();
}
// handle error cases for probe
var ip = findIp(domain);
if (probeResult instanceof DomainProber.ProbeResultError err) {
crawledDomainWriter.accept(
CrawledDomain.builder()
.crawlerStatus(err.status().name())
.crawlerStatusDesc(err.desc())
.id(id)
.domain(domain)
.ip(ip)
.build()
);
return 1;
}
if (probeResult instanceof DomainProber.ProbeResultRedirect redirect) {
crawledDomainWriter.accept(
CrawledDomain.builder()
.crawlerStatus(CrawlerDomainStatus.REDIRECT.name())
.crawlerStatusDesc("Redirected to different domain")
.redirectDomain(redirect.domain().toString())
.id(id)
.domain(domain)
.ip(ip)
.build()
);
return 1;
}
throw new IllegalStateException("Unknown probe result: " + probeResult);
};
private int crawlDomain() {
String ip = findIp(domain);
assert !crawlFrontier.isEmpty();
var robotsRules = fetcher.fetchRobotRules(crawlFrontier.peek().domain);
long crawlDelay = robotsRules.getCrawlDelay();
CrawledDomain ret = new CrawledDomain(id, domain, null, CrawlerDomainStatus.OK.name(), null, ip, new ArrayList<>(), null);
int fetchedCount = 0;
configureLinkFilter();
while (!crawlFrontier.isEmpty()
&& !crawlFrontier.isCrawlDepthReached()
&& errorCount < MAX_ERRORS)
{
var top = crawlFrontier.takeNextUrl();
if (!robotsRules.isAllowed(top.toString())) {
crawledDomainWriter.accept(createRobotsError(top));
continue;
}
if (!crawlFrontier.filterLink(top))
continue;
if (urlBlocklist.isUrlBlocked(top))
continue;
if (!isAllowedProtocol(top.proto))
continue;
if (top.toString().length() > 255)
continue;
if (!crawlFrontier.addVisited(top))
continue;
if (fetchDocument(top, crawlDelay)) {
fetchedCount++;
}
}
ret.cookies = fetcher.getCookies();
crawledDomainWriter.accept(ret);
return fetchedCount;
}
private void configureLinkFilter() {
try {
logger.info("Configuring link filter");
fetchUrl(crawlFrontier.peek())
.map(linkFilterSelector::selectFilter)
.ifPresent(crawlFrontier::setLinkFilter);
}
catch (Exception ex) {
logger.error("Error configuring link filter", ex);
}
}
private boolean fetchDocument(EdgeUrl top, long crawlDelay) {
logger.debug("Fetching {}", top);
long startTime = System.currentTimeMillis();
var doc = fetchUrl(top);
if (doc.isPresent()) {
var d = doc.get();
crawledDomainWriter.accept(d);
if (d.url != null) {
EdgeUrl.parse(d.url).ifPresent(crawlFrontier::addVisited);
}
if ("ERROR".equals(d.crawlerStatus) && d.httpStatus != 404) {
errorCount++;
}
}
long crawledTime = System.currentTimeMillis() - startTime;
delay(crawlDelay, crawledTime);
return doc.isPresent();
}
private boolean isAllowedProtocol(String proto) {
return proto.equalsIgnoreCase("http")
|| proto.equalsIgnoreCase("https");
}
private Optional<CrawledDocument> fetchUrl(EdgeUrl top) {
try {
var doc = fetchContent(top);
if (doc.documentBody != null) {
doc.documentBodyHash = createHash(doc.documentBody.decode());
Optional<Document> parsedDoc = parseDoc(doc);
EdgeUrl url = new EdgeUrl(doc.url);
parsedDoc.ifPresent(parsed -> findLinks(url, parsed));
parsedDoc.flatMap(parsed -> findCanonicalUrl(url, parsed))
.ifPresent(canonicalLink -> doc.canonicalUrl = canonicalLink.toString());
}
return Optional.of(doc);
}
catch (Exception ex) {
logger.warn("Failed to process document {}", top);
}
return Optional.empty();
}
@SneakyThrows
private CrawledDocument fetchContent(EdgeUrl top) {
for (int i = 0; i < 2; i++) {
try {
return fetcher.fetchContent(top);
}
catch (RateLimitException ex) {
slowDown = true;
int delay = ex.retryAfter();
if (delay > 0 && delay < 5000) {
Thread.sleep(delay);
}
}
}
return createRetryError(top);
}
private String createHash(String documentBodyHash) {
return hashMethod.hashUnencodedChars(documentBodyHash).toString();
}
private Optional<Document> parseDoc(CrawledDocument doc) {
if (doc.documentBody == null)
return Optional.empty();
return Optional.of(Jsoup.parse(doc.documentBody.decode()));
}
private void findLinks(EdgeUrl baseUrl, Document parsed) {
baseUrl = linkParser.getBaseLink(parsed, baseUrl);
for (var link : parsed.getElementsByTag("a")) {
linkParser.parseLink(baseUrl, link).ifPresent(crawlFrontier::addToQueue);
}
for (var link : parsed.getElementsByTag("frame")) {
linkParser.parseFrame(baseUrl, link).ifPresent(crawlFrontier::addToQueue);
}
for (var link : parsed.getElementsByTag("iframe")) {
linkParser.parseFrame(baseUrl, link).ifPresent(crawlFrontier::addToQueue);
}
for (var link : parsed.getElementsByTag("link")) {
String rel = link.attr("rel");
if (rel.equalsIgnoreCase("next") || rel.equalsIgnoreCase("prev")) {
linkParser.parseLink(baseUrl, link).ifPresent(crawlFrontier::addToQueue);
}
}
}
private Optional<EdgeUrl> findCanonicalUrl(EdgeUrl baseUrl, Document parsed) {
baseUrl = baseUrl.domain.toRootUrl();
for (var link : parsed.select("link[rel=canonical]")) {
return linkParser.parseLink(baseUrl, link);
}
return Optional.empty();
}
private String findIp(String domain) {
try {
return InetAddress.getByName(domain).getHostAddress();
} catch (UnknownHostException e) {
return "";
}
}
@SneakyThrows
private void delay(long sleepTime, long spentTime) {
if (testFlagIgnoreDelay)
return;
if (sleepTime >= 1) {
if (spentTime > sleepTime)
return;
Thread.sleep(min(sleepTime-spentTime, 5000));
}
else if (slowDown) {
Thread.sleep( 1000);
}
else {
// When no crawl delay is specified, lean toward twice the fetch+process time,
// within sane limits. This means slower servers get slower crawling, and faster
// servers get faster crawling.
sleepTime = spentTime * 2;
sleepTime = min(sleepTime, DEFAULT_CRAWL_DELAY_MAX_MS);
sleepTime = max(sleepTime, DEFAULT_CRAWL_DELAY_MIN_MS);
if (spentTime > sleepTime)
return;
Thread.sleep(sleepTime-spentTime);
}
}
private CrawledDocument createRobotsError(EdgeUrl url) {
return CrawledDocument.builder()
.url(url.toString())
.timestamp(LocalDateTime.now().toString())
.httpStatus(-1)
.crawlerStatus(CrawlerDocumentStatus.ROBOTS_TXT.name())
.build();
}
private CrawledDocument createRetryError(EdgeUrl url) {
return CrawledDocument.builder()
.url(url.toString())
.timestamp(LocalDateTime.now().toString())
.httpStatus(429)
.crawlerStatus(CrawlerDocumentStatus.ERROR.name())
.build();
}
private CrawledDomain createErrorPostFromStatus(FetchResult ret) {
String ip = findIp(domain);
if (ret.state == FetchResultState.ERROR) {
return CrawledDomain.builder()
.crawlerStatus(CrawlerDomainStatus.ERROR.name())
.id(id).domain(domain)
.ip(ip)
.build();
}
if (ret.state == FetchResultState.REDIRECT) {
return CrawledDomain.builder()
.crawlerStatus(CrawlerDomainStatus.REDIRECT.name())
.id(id)
.domain(domain)
.redirectDomain(ret.domain.toString())
.ip(ip)
.build();
}
throw new AssertionError("Unexpected case");
}
}