[TOC]

org.apache.nutch.scoring.webgraph

Class WebGraph

  • java.lang.Object
    • org.apache.hadoop.conf.Configured
    • org.apache.nutch.scoring.webgraph.WebGraph
    • All Implemented Interfaces:
    • org.apache.hadoop.conf.Configurable, org.apache.hadoop.util.Tool 
public class WebGraph
extends org.apache.hadoop.conf.Configured
implements org.apache.hadoop.util.Tool

Creates three databases, one for inlinks, one for outlinks, and a node database that holds the number of in and outlinks to a url and the current score for the url. The score is set by an analysis program such as LinkRank. The WebGraph is an update-able database. Outlinks are stored by their fetch time or by the current system time if no fetch time is available. Only the most recent version of outlinks for a given url is stored. As more crawls are executed and the WebGraph updated, newer Outlinks will replace older Outlinks. This allows the WebGraph to adapt to changes in the link structure of the web. The Inlink database is created from the Outlink database and is regenerated when the WebGraph is updated. The Node database is created from both the Inlink and Outlink databases. Because the Node database is overwritten when the WebGraph is updated and because the Node database holds current scores for urls it is recommended that a crawl-cyle (one or more full crawls) fully complete before the WebGraph is updated and some type of analysis, such as LinkRank, is run to update scores in the Node database in a stable fashion.

Nested Class Summary

Nested Classes Modifier and Type Class and Description static class WebGraph.OutlinkDb The OutlinkDb creates a database of all outlinks.

Field Summary

Fields Modifier and Type Field and Description static String INLINK_DIR static String LOCK_NAME static org.slf4j.Logger LOG static String NODE_DIR static String OLD_OUTLINK_DIR static String OUTLINK_DIR

Constructor Summary

Constructors Constructor and Description WebGraph()

Method Summary

Methods Modifier and Type Method and Description void createWebGraph(org.apache.hadoop.fs.Path webGraphDb, org.apache.hadoop.fs.Path[] segments, boolean normalize, boolean filter) Creates the three different WebGraph databases, Outlinks, Inlinks, and Node. static void main(String[] args) int run(String[] args) Parses command link arguments and runs the WebGraph jobs.

-

Methods inherited from class org.apache.hadoop.conf.Configured

getConf, setConf 

-

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait 

-

Methods inherited from interface org.apache.hadoop.conf.Configurable

getConf, setConf

Field Detail

-

LOG

public static final org.slf4j.Logger LOG
-

LOCK_NAME

public static final String LOCK_NAME
  - See Also:
  - [Constant Field Values](../../../../../constant-values.html#org.apache.nutch.scoring.webgraph.WebGraph.LOCK_NAME)       
-

INLINK_DIR

public static final String INLINK_DIR
  - See Also:
  - [Constant Field Values](../../../../../constant-values.html#org.apache.nutch.scoring.webgraph.WebGraph.INLINK_DIR)       
-

OUTLINK_DIR

public static final String OUTLINK_DIR
  - See Also:
  - [Constant Field Values](../../../../../constant-values.html#org.apache.nutch.scoring.webgraph.WebGraph.OUTLINK_DIR)       
-

OLD_OUTLINK_DIR

public static final String OLD_OUTLINK_DIR
  - See Also:
  - [Constant Field Values](../../../../../constant-values.html#org.apache.nutch.scoring.webgraph.WebGraph.OLD_OUTLINK_DIR)       
-

NODE_DIR

public static final String NODE_DIR
  - See Also:
  - [Constant Field Values](../../../../../constant-values.html#org.apache.nutch.scoring.webgraph.WebGraph.NODE_DIR)

Constructor Detail

-

WebGraph

public WebGraph()

Method Detail

-

createWebGraph

public void createWebGraph(org.apache.hadoop.fs.Path webGraphDb,
                  org.apache.hadoop.fs.Path[] segments,
                  boolean normalize,
                  boolean filter)
                    throws IOException

Creates the three different WebGraph databases, Outlinks, Inlinks, and Node. If a current WebGraph exists then it is updated, if it doesn't exist then a new WebGraph database is created.

  - Parameters:
  - <code>webGraphDb</code> - The WebGraph to create or update.
  - <code>segments</code> - The array of segments used to update the WebGraph. Newer segments and fetch times will overwrite older segments.
  - <code>normalize</code> - whether to use URLNormalizers on URL&#39;s in the segment
  - <code>filter</code> - whether to use URLFilters on URL&#39;s in the segment 
  - Throws: 
  - <code>IOException</code> - If an error occurs while processing the WebGraph.       
-

main

public static void main(String[] args)
                 throws Exception
  - Throws: 
  - <code>Exception</code>       
-

run

public int run(String[] args)
        throws Exception

Parses command link arguments and runs the WebGraph jobs.

  - Specified by: 
  - <code>run</code> in interface <code>org.apache.hadoop.util.Tool</code> 
  - Throws: 
  - <code>Exception</code>

Copyright © 2014 The Apache Software Foundation