Sorry for replying so late. I just created an JIRA ticket - https://issues.apache.org/jira/browse/MAPREDUCE-2419.
Gerald On Wed, Jan 5, 2011 at 7:34 PM, Greg Roelofs <[email protected]> wrote: > Zhenhua Guo <[email protected]> wrote: > >> It seems that mapred.task.cache.levels is used by JobTracker to create >> task caches for nodes at various levels. This makes data-locality >> scheduling possible. >> If I set mapred.task.cache.levels to 0 and use default network >> topology, then mapreduce job will stall forever. The reason is >> JobInProgress::findNewMapTask always returns -1. Field >> "nonRunningMapCache" is empty and field "nonLocalMaps" is also empty. >> I wonder whether it is designed to behave like that. Or when >> mapred.task.cache.levels is set 0, Hadoop should fall back to some >> default caching strategy. E.g. put all tasks into >> JobInProgress::nonLocalMaps. > > I think there should either be a fallback mechanism or the code should > disallow/ignore values less than 1. Can you file a JIRA issue for this? > https://issues.apache.org/jira/secure/CreateIssue!default.jspa > > Thanks, > Greg >
