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star commented on HDFS-14370: ----------------------------- [~xkrogen], agree. Server side handler as limited resource should not be blocked. {quote}This is similar to how the NN, when it wants a client to backoff due to load, throws a backoff exception and expects the client to act accordingly. {quote} > Edit log tailing fast-path should allow for backoff > --------------------------------------------------- > > Key: HDFS-14370 > URL: https://issues.apache.org/jira/browse/HDFS-14370 > Project: Hadoop HDFS > Issue Type: Improvement > Components: namenode, qjm > Affects Versions: 3.3.0 > Reporter: Erik Krogen > Assignee: Erik Krogen > Priority: Major > > As part of HDFS-13150, in-progress edit log tailing was changed to use an > RPC-based mechanism, thus allowing the edit log tailing frequency to be > turned way down, and allowing standby/observer NameNodes to be only a few > milliseconds stale as compared to the Active NameNode. > When there is a high volume of transactions on the system, each RPC fetches > transactions and takes some time to process them, self-rate-limiting how > frequently an RPC is submitted. In a lightly loaded cluster, however, most of > these RPCs return an empty set of transactions, consuming a high > (de)serialization overhead for very little benefit. This was reported by > [~jojochuang] in HDFS-14276 and I have also seen it on a test cluster where > the SbNN was submitting 8000 RPCs per second that returned empty. > I propose we add some sort of backoff to the tailing, so that if an empty > response is received, it will wait a longer period of time before submitting > a new RPC. -- This message was sent by Atlassian JIRA (v7.6.3#76005) --------------------------------------------------------------------- To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org