com.digitalpebble.storm.crawler.protocol.http.HttpRobotRulesParser.java Source code

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Here is the source code for com.digitalpebble.storm.crawler.protocol.http.HttpRobotRulesParser.java

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/**
 * 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.http;

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;
    }
}