Re: Reducers spawned when mapred.reduce.tasks=0
Instantiation of Reducer is moved to the place where reduce() is getting called, in branch 0.19.1. See HADOOP-5002. Hope that should solve your issue with configure() method. Thanks Amareshwari Chris K Wensel wrote: fwiw, we have released a workaround for this issue in Cascading 1.0.5. http://www.cascading.org/ http://cascading.googlecode.com/files/cascading-1.0.5.tgz In short, Hadoop 0.19.0 and .1 instantiate the users Reducer class and subsequently calls configure() when there is no intention to use the class (during job/task cleanup tasks). This clearly can cause havoc for users who use configure() to initialize resources used by the reduce() method. Testing for jobConf.getNumReduceTasks() is 0 inside the configure() method seems to work out well. branch-0.19 looks like it won't instantiate the Reducer class during job/task cleanup tasks, so I expect will leak into future releases. cheers, ckw On Mar 12, 2009, at 8:20 PM, Amareshwari Sriramadasu wrote: Are you seeing reducers getting spawned from web ui? then, it is a bug. If not, there won't be reducers spawned, it could be job-setup/ job-cleanup task that is running on a reduce slot. See HADOOP-3150 and HADOOP-4261. -Amareshwari Chris K Wensel wrote: May have found the answer, waiting on confirmation from users. Turns out 0.19.0 and .1 instantiate the reducer class when the task is actually intended for job/task cleanup. branch-0.19 looks like it resolves this issue by not instantiating the reducer class in this case. I've got a workaround in the next maint release: http://github.com/cwensel/cascading/tree/wip-1.0.5 ckw On Mar 12, 2009, at 10:12 AM, Chris K Wensel wrote: Hey all Have some users reporting intermittent spawning of Reducers when the job.xml shows mapred.reduce.tasks=0 in 0.19.0 and .1. This is also confirmed when jobConf is queried in the (supposedly ignored) Reducer implementation. In general this issue would likely go unnoticed since the default reducer is IdentityReducer. but since it should be ignored in the Mapper only case, we don't bother not setting the value, and subsequently comes to ones attention rather abruptly. am happy to open a JIRA, but wanted to see if anyone else is experiencing this issue. note the issue seems to manifest with or without spec exec. ckw --Chris K Wensel ch...@wensel.net http://www.cascading.org/ http://www.scaleunlimited.com/ --Chris K Wensel ch...@wensel.net http://www.cascading.org/ http://www.scaleunlimited.com/ -- Chris K Wensel ch...@wensel.net http://www.cascading.org/ http://www.scaleunlimited.com/
Re: Reducers spawned when mapred.reduce.tasks=0
fwiw, we have released a workaround for this issue in Cascading 1.0.5. http://www.cascading.org/ http://cascading.googlecode.com/files/cascading-1.0.5.tgz In short, Hadoop 0.19.0 and .1 instantiate the users Reducer class and subsequently calls configure() when there is no intention to use the class (during job/task cleanup tasks). This clearly can cause havoc for users who use configure() to initialize resources used by the reduce() method. Testing for jobConf.getNumReduceTasks() is 0 inside the configure() method seems to work out well. branch-0.19 looks like it won't instantiate the Reducer class during job/task cleanup tasks, so I expect will leak into future releases. cheers, ckw On Mar 12, 2009, at 8:20 PM, Amareshwari Sriramadasu wrote: Are you seeing reducers getting spawned from web ui? then, it is a bug. If not, there won't be reducers spawned, it could be job-setup/ job- cleanup task that is running on a reduce slot. See HADOOP-3150 and HADOOP-4261. -Amareshwari Chris K Wensel wrote: May have found the answer, waiting on confirmation from users. Turns out 0.19.0 and .1 instantiate the reducer class when the task is actually intended for job/task cleanup. branch-0.19 looks like it resolves this issue by not instantiating the reducer class in this case. I've got a workaround in the next maint release: http://github.com/cwensel/cascading/tree/wip-1.0.5 ckw On Mar 12, 2009, at 10:12 AM, Chris K Wensel wrote: Hey all Have some users reporting intermittent spawning of Reducers when the job.xml shows mapred.reduce.tasks=0 in 0.19.0 and .1. This is also confirmed when jobConf is queried in the (supposedly ignored) Reducer implementation. In general this issue would likely go unnoticed since the default reducer is IdentityReducer. but since it should be ignored in the Mapper only case, we don't bother not setting the value, and subsequently comes to ones attention rather abruptly. am happy to open a JIRA, but wanted to see if anyone else is experiencing this issue. note the issue seems to manifest with or without spec exec. ckw -- Chris K Wensel ch...@wensel.net http://www.cascading.org/ http://www.scaleunlimited.com/ -- Chris K Wensel ch...@wensel.net http://www.cascading.org/ http://www.scaleunlimited.com/ -- Chris K Wensel ch...@wensel.net http://www.cascading.org/ http://www.scaleunlimited.com/
Reducers spawned when mapred.reduce.tasks=0
Hey all Have some users reporting intermittent spawning of Reducers when the job.xml shows mapred.reduce.tasks=0 in 0.19.0 and .1. This is also confirmed when jobConf is queried in the (supposedly ignored) Reducer implementation. In general this issue would likely go unnoticed since the default reducer is IdentityReducer. but since it should be ignored in the Mapper only case, we don't bother not setting the value, and subsequently comes to ones attention rather abruptly. am happy to open a JIRA, but wanted to see if anyone else is experiencing this issue. note the issue seems to manifest with or without spec exec. ckw -- Chris K Wensel ch...@wensel.net http://www.cascading.org/ http://www.scaleunlimited.com/
