[ http://issues.apache.org/jira/browse/HADOOP-563?page=comments#action_12438231 ] Yoram Arnon commented on HADOOP-563: ------------------------------------
accelerating lease requests may not be the right approach, given that the typical use case is that the name node is so busy that it wasn't able to reply within half the lease period. accelerating requests makes sense prior to STONITH, and then the other node should have a high priority thread to reply or risk death, that's clearly not the case here. Seems like backing off requests is a better policy than accelerating requests. > DFS client should try to re-new lease if it gets a lease expiration exception > when it adds a block to a file > ------------------------------------------------------------------------------------------------------------ > > Key: HADOOP-563 > URL: http://issues.apache.org/jira/browse/HADOOP-563 > Project: Hadoop > Issue Type: Bug > Reporter: Runping Qi > > In the current DFS client implementation, there is one thread responsible for > renewing leases. If for whatever reason, that thread runs behind, the lease > may get expired. That causes the client gets a lease expiration exception > when writing a block. The consequence of that is very devastating: the client > can no longer write to the file, and all the partial results up to that point > are gone! This is especially costly for some map reduce jobs where a reducer > may take hours or even days to sort the intermediate results before the > actual reducing work can start. > The problem will be solved if the flush method of DFS client can renew lease > on demand. That is, it should try to re-new lease when it catches a lease > expiration exception. That way, even when under heavy load and the lease > renewing thread runs behind, the reducer task (or what ever tasks use that > client) can preceed. That will be a huge saving in some cases (where sorting > intermediate results take a long time to finish). We can set a limit on the > number of retries, and may even make it configurable (or changeable at > runtime). > The namenode can use a different expiration time that is much higher than the > current 1 minute lease expiration time for cleaning up the abandoned > unclosed files. > -- 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
