crawler-ninja/index.js

var events      = require('events');
var timers      = require('timers');
var util        = require("util");
var _           = require("underscore");
var requester   = require("./lib/queue-requester");
var URI         = require('./lib/uri.js');
var Map         = require("collections/fast-map");
var Set         = require("collections/fast-set");
var html        = require("./lib/html.js");
var domainBlackList  = require("./default-lists/domain-black-list.js").list();

var DEFAULT_NUMBER_OF_CONNECTIONS = 10;
var DEFAULT_DEPTH_LIMIT = -1; // no limit
var DEFAULT_TIME_OUT = 20000;
var DEFAULT_RETRIES = 3;
var DEFAULT_RETRY_TIMEOUT = 10000;
var DEFAULT_SKIP_DUPLICATES = true;
var DEFAULT_RATE_LIMITS = 0;
var DEFAULT_MAX_ERRORS = 5;
var DEFAULT_ERROR_RATES = [200, 350, 500];

var DEFAULT_CRAWL_EXTERNAL_LINKS = false;
var DEFAULT_CRAWL_EXTERNAL_DOMAINS = false;
var DEFAULT_CRAWL_SCRIPTS = true;   // Crawl <script>
var DEFAULT_CRAWL_LINKS = true;     // Crawl <link>
var DEFAULT_CRAWL_IMAGES = true;

var DEFAULT_PROTOCOLS_TO_CRAWL = ["http", "https"];
var DEFAULT_FOLLOW_301 = false;

var DEFAULT_LINKS_TYPES = ["canonical", "stylesheet"];
var DEFAULT_USER_AGENT = "NinjaBot";
var DEFAULT_CACHE = false;
var DEFAULT_METHOD = 'GET';
var DEFAULT_REFERER = false;

/**
 * The crawler object
 *
 * @param config used to customize the crawler.
 *
 *  The current config attributes are :
 *  - maxConnections     : the number of connections used to crawl - default is 10
 *  - externalLinks      : if true crawl external links
 *  - externalDomains    : if true crawl the complete external domains. This option can crawl a lot of different domains
 *  - scripts            : if true crawl script tags
 *  - links              : if true crawl link tags
 *  - linkTypes          : the type of the links tags to crawl (match to the rel attribute), default : ["canonical", "stylesheet"]
 *  - images             : if true crawl images
 *  - protocols          : list of the protocols to crawl, default = ["http", "https"]
 *  - timeout            : timeout per requests in milliseconds (Default 20000)
 *  - retries            : number of retries if the request fails (default 3)
 *  - retryTimeout       : number of milliseconds to wait before retrying (Default 10000)
 *  - maxErrors          : number of timeout errors before changing the crawl rate, default is 5,
    - errorRates         : list of rates to used when too many timeout errors occur.
 *  - skipDuplicates     : if true skips URIs that were already crawled - default is true
 *  - rateLimits         : number of milliseconds to delay between each requests (Default 0).
 *                         Note that this option will force crawler to use only one connection
 *  - depthLimit         : the depth limit for the crawl
 *  - followRedirect     : if true, the crawl will not return the 301, it will follow directly the redirection
 *  - proxyList          : the list of proxies (see the project simple-proxies on npm)
 *
 *  + all options provided by nodejs request : https://github.com/request/request
 */
function Crawler(config) {


    // Store the depth for each crawled url
    // Override config.updateDepth function in order to use another storage
    // This default implementation is not recommanded for big crawl
    // TODO : use an external store
    this.depthUrls = new Map();

    // list of the hosts from which the crawl starts
    this.startFromHosts = new Set();

    // Default config
    this.config = this.createDefaultConfig();

    // Merge default config values & overridden values provided by the arg config
    if (config) {
      _.extend(this.config, config);
    }

    // if using rateLimits we want to use only one connection with delay between requests
    if (this.config.rateLimits !== 0) {
        this.config.maxConnections = 1;
    }


    // assign the default updateDepth method used to calculate the crawl depth
    this.updateDepth = updateDepth;

    // If the config object contains an new implementation of the updateDepth method
    if (this.config.updateDepth) {
      this.updateDepth = this.config.updateDepth;
    }

    this.httpRequester = new requester.Requester(this.config);

    events.EventEmitter.call(this);

}

util.inherits(Crawler, events.EventEmitter);


/**
 * Add one or more urls to crawl
 *
 * @param The url to crawl
 *
 */
Crawler.prototype.queue = function(options) {

    var self = this;

    // Error if no options
    if (! options)  {
        if (self.config.onCrawl) {
            self.config.onCrawl({errorCode : "NO_OPTIONS"}, {method:"GET", url : "unknown", proxy : "", error : true});
        }

        if (this.httpRequester.idle()) {
          self.config.onDrain();
        }
        return;
    }


    // if Array => recall this method for each element
    if (_.isArray(options)) {
        options.forEach(function(opt){
            self.queue(opt);
        });

        return;
    }


    // if String, we expect to receive an url
    if (_.isString(options)) {
      this.startFromHosts.add(URI.host(options));
      this.httpRequester.queue(this.addDefaultOptions({uri:options, url:options}, this.config))
    }
    // Last possibility, this is a json
    else {

      if (! _.has(options, "url") && ! _.has(options, "uri")) {
        if (self.config.onCrawl) {
            self.config.onCrawl({errorCode : "NO_URL_OPTION"}, {method:"GET", url : "unknown", proxy : "", error : true});
        }

        if (this.httpRequester.idle()) {
          self.config.onDrain();
        }
      }
      else {
        this.startFromHosts.add(URI.host(_.has(options, "url") ? options.url : options.uri));
        this.httpRequester.queue(this.addDefaultOptions(options, this.config));
      }
    }


}

Crawler.prototype.addDefaultOptions = function(options, defaultOptions) {

    _.defaults(options, defaultOptions);
    options.maxRetries = options.retries;
    return options;

}

Crawler.prototype.buildNewOptions = function(options, newUrl) {

    var o = this.createDefaultConfig(newUrl);

    // Copy only options attributes that are in the options used for the previous request
    // Could be simple ? ;-)
    o =  _.extend(o, _.pick(options, _.without(_.keys(o), "url", "uri") ));

    //Reset setting used for retries when an error occurs like a timeout
    o.maxRetries = o.retries;


    if (options.canCrawl) {
      o.canCrawl = options.canCrawl;
    }
    return o;

}


/**
 * Default crawler config
 *
 * @returns the config object
 */
Crawler.prototype.createDefaultConfig = function(url) {
  var self = this;
  var config = {


      cache                   : DEFAULT_CACHE,
      method                  : DEFAULT_METHOD,
      referer                 : DEFAULT_REFERER,
      maxConnections          : DEFAULT_NUMBER_OF_CONNECTIONS,
      timeout                 : DEFAULT_TIME_OUT,
      retries                 : DEFAULT_RETRIES,
      maxRetries              : DEFAULT_RETRIES,
      retryTimeout            : DEFAULT_RETRY_TIMEOUT,
      maxErrors               : DEFAULT_MAX_ERRORS,
      errorRates              : DEFAULT_ERROR_RATES,
      skipDuplicates          : DEFAULT_SKIP_DUPLICATES,
      rateLimits              : DEFAULT_RATE_LIMITS,
      externalLinks           : DEFAULT_CRAWL_EXTERNAL_LINKS,
      externalDomains         : DEFAULT_CRAWL_EXTERNAL_DOMAINS,
      protocols               : DEFAULT_PROTOCOLS_TO_CRAWL,
      depthLimit              : DEFAULT_DEPTH_LIMIT,
      followRedirect          : DEFAULT_FOLLOW_301,
      images                  : DEFAULT_CRAWL_IMAGES,
      links                   : DEFAULT_CRAWL_LINKS,
      linkTypes               : DEFAULT_LINKS_TYPES,
      scripts                 : DEFAULT_CRAWL_SCRIPTS,
      userAgent               : DEFAULT_USER_AGENT,
      domainBlackList       : domainBlackList,

      onCrawl : function(error, result){
        self.crawl(error, result);
      },

      onDrain : function(){
        timers.setImmediate(function(){
            self.emit('end');
        });

      }

  };

  if (url) {
    config.url = url;
    config.uri = url;
  }

  return config;

}

/**
 * Default callback function used when the http queue requester get a resource (html, pdf, css, ...)
 *
 * @param error The usual nodejs error
 * @param result : the result of the resource crawl
 * @param the jquery like object for accessing to the HTML tags. Null is the resource
 *        is not an HTML
 */
Crawler.prototype.crawl = function (error, result) {


    var self = this;
    if (error) {
        //console.log(error);
        timers.setImmediate(emitErrorEvent, self, error, result);
        return;
    }

    var $ = html.isHTML(result.body) ? html.$(result.body) : null;

    timers.setImmediate(emitCrawlEvent, self,result, $);

    // if $ is defined, this is an HTML page with an http status 200
    if ($) {
      this.analyzeHTML(result,$);
    }


    // if 30* & followRedirect = false => chain 30*
    if (result.statusCode >= 300 && result.statusCode <= 399  &&  ! this.config.followRedirect) {

        var from = result.uri;
        var to = result.headers["location"];
        var to = URI.linkToURI(from, to);
        timers.setImmediate(emitRedirectEvent, self, from, to, result.statusCode);

        this.httpRequester.queue(this.buildNewOptions(result,to));

    }
}



/**
 * Analyze an HTML page. Mainly, found a.href & links in the page
 *
 * @param result : the result of the crawled resource
 * @param the jquery like object for accessing to the HTML tags. Null is the resource
 *        is not an HTML
 */
Crawler.prototype.analyzeHTML = function(result, $) {


    this.crawlHrefs(result, $);

    if (this.config.links){
        this.crawlLinks(result, $);
    }

    if (this.config.scripts) {
        this.crawlScripts(result,$);
    }

    if (this.config.images) {
      this.crawlImages(result,$);
    }


}


/**
 * Crawl urls that match to HTML tags a.href found in one page
 *
 * @param result : the result of the crawled resource
 * @param the jquery like object for accessing to the HTML tags.
 *
 */
Crawler.prototype.crawlHrefs = function(result, $) {
  var parentUri = result.uri
  var self = this;

  $('a').each(function(index, a) {

      var link = $(a).attr('href');

      if (link) {

        var anchor = $(a).text() ? $(a).text() : "";
        var noFollow = $(a).attr("rel");
        var isDoFollow =  ! (noFollow && noFollow === "nofollow");

        var linkUri = URI.linkToURI(parentUri, link);

        var currentDepth = self.updateDepth(parentUri, linkUri);

        timers.setImmediate(emitCrawlHrefEvent, self, "crawlLink", parentUri, linkUri, anchor, isDoFollow);


        if (self.isAGoodLinkToCrawl(result, currentDepth, parentUri, linkUri, anchor, isDoFollow)) {
          self.httpRequester.queue(self.buildNewOptions(result,linkUri));
        }
        else {
          timers.setImmediate(emitCrawlHrefEvent, self, "uncrawl", parentUri, linkUri, anchor, isDoFollow);
        }
      }

  });

}

/**
 * Crawl link tags found in the HTML page
 * eg. : <link rel="stylesheet" href="/css/bootstrap.min.css">
 *
 * @param result : the result of the crawled resource
 * @param the jquery like object for accessing to the HTML tags.
 */
Crawler.prototype.crawlLinks = function(result, $) {

  var parentUri = result.uri;
  var self = this;

  $('link').each(function(index, linkTag) {

      var link = $(linkTag).attr('href');

      if (link) {

          var rel =  $(linkTag).attr('rel');

          if (self.config.linkTypes.indexOf(rel) > 0) {
              var linkUri = URI.linkToURI(parentUri, link);
              var currentDepth = self.updateDepth(parentUri, linkUri);

              timers.setImmediate(emitCrawlLinkEvent, self, parentUri, linkUri);

              if (self.isAGoodLinkToCrawl(result, currentDepth, parentUri, linkUri)) {

                self.httpRequester.queue(self.buildNewOptions(result,linkUri));

              }
              else {
                timers.setImmediate(emitUnCrawlEvent, self, parentUri, linkUri);
              }
          }

      }

  });

}

/**
 * Crawl script tags found in the HTML page
 *
 * @param result : the result of the crawled resource
 * @param the jquery like object for accessing to the HTML tags.
 */
Crawler.prototype.crawlScripts = function(result, $) {

  var parentUri = result.uri;
  var self = this;

  $('script').each(function(index, link) {

      var link = $(link).attr('src');
      if (link) {
        var linkUri = URI.linkToURI(parentUri, link);
        var currentDepth = self.updateDepth(parentUri, linkUri);

        timers.setImmediate(emitCrawlLinkEvent, self, parentUri, linkUri);

        if (self.isAGoodLinkToCrawl(result, currentDepth, parentUri, linkUri)) {

          self.httpRequester.queue(self.buildNewOptions(result, linkUri));

        }
        else {
          timers.setImmediate(emitUnCrawlEvent, self, parentUri, linkUri);
        }
      }

  });

}

/**
 * Crawl image tags found in the HTML page
 *
 * @param result : the result of the crawled resource
 * @param the jquery like object for accessing to the HTML tags.
 */
Crawler.prototype.crawlImages = function(result, $) {

  var parentUri = result.uri;
  var self = this;

  $('img').each(function(index, img) {

      var link = $(img).attr('src');
      var alt = $(img).attr('alt');
      if (link) {
        var linkUri = URI.linkToURI(parentUri, link);

        var currentDepth = self.updateDepth(parentUri, linkUri);

        timers.setImmediate(emitCrawlImage, self, parentUri, linkUri, alt);

        if (self.isAGoodLinkToCrawl(result, currentDepth, parentUri, linkUri)) {

          self.httpRequester.queue(self.buildNewOptions(result,linkUri));

        }
        else {
          timers.setImmediate(emitUnCrawlEvent, self, parentUri, linkUri);
        }
      }

  });

}

/**
 * Check if a link has to be crawled
 *
 * @param the link url
 * @param the anchor text of the links
 * @param true if the link is dofollow
 * @returns
 */
Crawler.prototype.isAGoodLinkToCrawl = function(result, currentDepth, parentUri, link, anchor, isDoFollow) {

  // 1. Check the depthLimit
  if (result.depthLimit > -1 && currentDepth > result.depthLimit) {
    return false
  }

  // 2. Check if we need to crawl external links
  if (URI.isExternalLink(parentUri,link) &&  ! result.externalLinks) {
    return false;
  }

  // 3. Check if we need to crawl external domains
  if (! this.startFromHosts.has(URI.host(parentUri)) && ! result.externalDomains) {
    return false;
  }

  // 4. Check if the link is based on a good protocol
  if (result.protocols.indexOf(URI.protocol(link)) < 0) {
    return false;
  }

  // 5. Check if the domain is in the black-list
  if (result.domainBlackList.indexOf(URI.domainName(link)) > 0) {

    return false;
  }

  // 6. Check if there is a rule in the crawler configuration
  if (! result.canCrawl) {
    return true;
  }

  var check =  result.canCrawl(parentUri, link, anchor, isDoFollow);
  //console.log(parentUri + " - " + link + " : " + check);
  return check;
}

/**
 * Compute the crawl depth for a link in function of the crawl depth
 * of the page that contains the link
 *
 * @param The URI of page that contains the link
 * @param The link for which the crawl depth has to be calculated
 * @returns the crawl depth of the link
 *
 */
var updateDepth = function(parentUri, linkUri) {

    if (this.depthUrls.has(parentUri)) {

        var parentDepth = this.depthUrls.get(parentUri);
        if (this.depthUrls.has(linkUri)) {
            return this.depthUrls.get(linkUri);
        }
        else {
          var depth = parentDepth + 1;
          this.depthUrls.set(linkUri, depth);
          return depth;
        }
    }
    else {
        this.depthUrls.set(parentUri, 0);
        this.depthUrls.set(linkUri, 1);
        return 1;
    }


}

function emitCrawlEvent(crawler, result, $) {

  crawler.emit("crawl", result, $);
}

function emitErrorEvent(crawler, error, result) {
  crawler.emit("error", error, result);
}

function emitRedirectEvent(crawler, from, to, statusCode) {
  crawler.emit("crawlRedirect", from, to, statusCode);
}


function emitCrawlHrefEvent(crawler, eventName, parentUri, linkUri, anchor, isDoFollow) {
  crawler.emit(eventName, parentUri, linkUri, anchor, isDoFollow);
}

function emitCrawlLinkEvent(crawler, parentUri, linkUri ) {
  crawler.emit("crawlLink", parentUri, linkUri);
}

function emitUnCrawlEvent(crawler, parentUri, linkUri ) {
  crawler.emit("uncrawl", parentUri, linkUri);
}

function emitCrawlImage(crawler, parentUri, linkUri, alt ) {

  crawler.emit("crawlImage", parentUri, linkUri, alt);
}

module.exports.Crawler = Crawler;