[ http://issues.apache.org/jira/browse/NUTCH-136?page=comments#action_12363886 ]
Florent Gluck commented on NUTCH-136: ------------------------------------- On my setup of 5 boxes (4 slaves, 1 master), I confirm that what Dominik Friedrich suggested fixes the missing urls I've been encountering for a while. I simply moved the following properties from nutch-site.xml to mapred-default.xml: <property> <name>mapred.map.tasks</name> <value>100</value> <description>The default number of map tasks per job. Typically set to a prime several times greater than number of available hosts. Ignored when mapred.job.tracker is "local". </description> </property> <property> <name>mapred.reduce.tasks</name> <value>40</value> <description>The default number of reduce tasks per job. Typically set to a prime close to the number of available hosts. Ignored when mapred.job.tracker is "local". </description> </property>/ After injecting 100'000 urls and doing a single pass crawl, I grepped the logs on my 4 slaves and confirmed that the sum of all the fetching attemps adds up to exactly 100'000. Therefore, there is no need to modify Generator.java. I also ran some tests with protocol-http and protocol-httpclient and verified that they give similar results. No missing urls in both cases. --Florent > mapreduce segment generator generates 50 % less than excepted urls > -------------------------------------------------------------------- > > Key: NUTCH-136 > URL: http://issues.apache.org/jira/browse/NUTCH-136 > Project: Nutch > Type: Bug > Versions: 0.8-dev > Reporter: Stefan Groschupf > Priority: Critical > > We notice that segments generated with the map reduce segment generator > contains only 50 % of the expected urls. We had a crawldb with 40 000 urls > and the generate commands only created a 20 000 pages segment. This also > happened with the topN parameter, we everytime got around 50 % of the > expected urls. > I tested the PartitionUrlByHost and it looks like it does its work. However > we fixed the problem by changing two things: > First we set the partition to a normal hashPartitioner. > Second we changed Generator.java line 48: > limit = job.getLong("crawl.topN",Long.MAX_VALUE)/job.getNumReduceTasks(); > to: > limit = job.getLong("crawl.topN",Long.MAX_VALUE); > Now it works as expected. > Has anyone a idea what the real source of this problem can be? > In general this is bug has the effect that all map reduce users fetch only 50 > % of it's urls per iteration. -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://issues.apache.org/jira/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira
