/**
* Licensed to DigitalPebble Ltd under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* DigitalPebble licenses this file to You 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.digitalpebble.storm.crawler.protocol;
import java.net.URL;
import java.util.Locale;
import org.apache.commons.lang.StringUtils;
import backtype.storm.Config;
import com.digitalpebble.storm.crawler.Metadata;
import com.digitalpebble.storm.crawler.protocol.HttpHeaders;
import com.digitalpebble.storm.crawler.protocol.Protocol;
import com.digitalpebble.storm.crawler.protocol.ProtocolResponse;
import com.digitalpebble.storm.crawler.protocol.RobotRulesParser;
import com.digitalpebble.storm.crawler.util.ConfUtils;
import crawlercommons.robots.BaseRobotRules;
/**
* This class is used for parsing robots for urls belonging to HTTP protocol. It
* extends the generic {@link RobotRulesParser} class and contains Http protocol
* specific implementation for obtaining the robots file.
*/
public class HttpRobotRulesParser extends RobotRulesParser {
protected boolean allowForbidden = false;
HttpRobotRulesParser() {
}
public HttpRobotRulesParser(Config conf) {
setConf(conf);
}
@Override
public void setConf(Config conf) {
super.setConf(conf);
allowForbidden = ConfUtils.getBoolean(conf, "http.robots.403.allow",
true);
}
/**
* Compose unique key to store and access robot rules in cache for given URL
*/
protected static String getCacheKey(URL url) {
String protocol = url.getProtocol().toLowerCase(Locale.ROOT); // normalize
// to
// lower
// case
String host = url.getHost().toLowerCase(Locale.ROOT); // normalize to
// lower case
int port = url.getPort();
if (port == -1) {
port = url.getDefaultPort();
}
/*
* Robot rules apply only to host, protocol, and port where robots.txt
* is hosted (cf. NUTCH-1752). Consequently
*/
String cacheKey = protocol + ":" + host + ":" + port;
return cacheKey;
}
/**
* Get the rules from robots.txt which applies for the given {@code url}.
* Robot rules are cached for a unique combination of host, protocol, and
* port. If no rules are found in the cache, a HTTP request is send to fetch
* {{protocol://host:port/robots.txt}}. The robots.txt is then parsed and
* the rules are cached to avoid re-fetching and re-parsing it again.
*
* @param http
* The {@link Protocol} object
* @param url
* URL robots.txt applies to
*
* @return {@link BaseRobotRules} holding the rules from robots.txt
*/
@Override
public BaseRobotRules getRobotRulesSet(Protocol http, URL url) {
String cacheKey = getCacheKey(url);
BaseRobotRules robotRules = CACHE.get(cacheKey);
boolean cacheRule = true;
if (robotRules == null) { // cache miss
URL redir = null;
LOG.trace("cache miss {}", url);
try {
ProtocolResponse response = http.getProtocolOutput(new URL(url,
"/robots.txt").toString(), Metadata.empty);
// try one level of redirection ?
if (response.getStatusCode() == 301
|| response.getStatusCode() == 302) {
String redirection = response.getMetadata().getFirstValue(
HttpHeaders.LOCATION);
if (StringUtils.isNotBlank(redirection)) {
if (!redirection.startsWith("http")) {
// RFC says it should be absolute, but apparently it
// isn't
redir = new URL(url, redirection);
} else {
redir = new URL(redirection);
}
response = http.getProtocolOutput(redir.toString(),
Metadata.empty);
}
}
if (response.getStatusCode() == 200) // found rules: parse them
{
String ct = response.getMetadata().getFirstValue(
HttpHeaders.CONTENT_TYPE);
robotRules = parseRules(url.toString(),
response.getContent(), ct, agentNames);
} else if ((response.getStatusCode() == 403)
&& (!allowForbidden))
robotRules = FORBID_ALL_RULES; // use forbid all
else if (response.getStatusCode() >= 500) {
cacheRule = false;
robotRules = EMPTY_RULES;
} else
robotRules = EMPTY_RULES; // use default rules
} catch (Throwable t) {
LOG.info("Couldn't get robots.txt for {} : {}", url,
t.toString());
cacheRule = false;
robotRules = EMPTY_RULES;
}
if (cacheRule) {
CACHE.put(cacheKey, robotRules); // cache rules for host
if (redir != null
&& !redir.getHost().equalsIgnoreCase(url.getHost())) {
// cache also for the redirected host
CACHE.put(getCacheKey(redir), robotRules);
}
}
}
return robotRules;
}
}