Niels Basjes created MAPREDUCE-5928: ---------------------------------------
Summary: Deadlock allocating containers for mappers and reducers Key: MAPREDUCE-5928 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5928 Project: Hadoop Map/Reduce Issue Type: Bug Environment: Hadoop 2.4.0 (as packaged by HortonWorks in HDP 2.1.2) Reporter: Niels Basjes I have a small cluster consisting of 8 desktop class systems (1 master + 7 workers). Due to the small memory of these systems I configured yarn as follows: {quote} yarn.nodemanager.resource.memory-mb = 2200 yarn.scheduler.minimum-allocation-mb = 250 {quote} On my client I did {quote} mapreduce.map.memory.mb = 512 mapreduce.reduce.memory.mb = 512 {quote} Now I run a job with 27 mappers and 32 reducers. After a while I saw this deadlock occur: - All nodes had been filled to their maximum capacity with reducers. - 1 Mapper was waiting for a container slot to start in. I tried killing reducer attempts but that didn't help (new reducer attempts simply took the existing container). *Workaround*: I set this value from my job. The default value is 0.05 (= 5%) {quote} mapreduce.job.reduce.slowstart.completedmaps = 0.99f {quote} -- This message was sent by Atlassian JIRA (v6.2#6252)