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Hudson commented on HDFS-7858: ------------------------------ FAILURE: Integrated in Hadoop-Hdfs-trunk #2197 (See [https://builds.apache.org/job/Hadoop-Hdfs-trunk/2197/]) HDFS-7858. Improve HA Namenode Failover detection on the client. (asuresh) (Arun Suresh: rev 030fcfa99c345ad57625486eeabedebf2fd4411f) * hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/retry/MultiException.java * hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ha/RequestHedgingProxyProvider.java * hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt * hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSHighAvailabilityWithQJM.md * hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSHighAvailabilityWithNFS.md * hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/ha/ConfiguredFailoverProxyProvider.java * hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/retry/RetryInvocationHandler.java * hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/ha/TestRequestHedgingProxyProvider.java > Improve HA Namenode Failover detection on the client > ---------------------------------------------------- > > Key: HDFS-7858 > URL: https://issues.apache.org/jira/browse/HDFS-7858 > Project: Hadoop HDFS > Issue Type: Improvement > Components: hdfs-client > Reporter: Arun Suresh > Assignee: Arun Suresh > Labels: BB2015-05-TBR > Fix For: 2.8.0 > > Attachments: HDFS-7858.1.patch, HDFS-7858.10.patch, > HDFS-7858.10.patch, HDFS-7858.11.patch, HDFS-7858.12.patch, > HDFS-7858.13.patch, HDFS-7858.2.patch, HDFS-7858.2.patch, HDFS-7858.3.patch, > HDFS-7858.4.patch, HDFS-7858.5.patch, HDFS-7858.6.patch, HDFS-7858.7.patch, > HDFS-7858.8.patch, HDFS-7858.9.patch > > > In an HA deployment, Clients are configured with the hostnames of both the > Active and Standby Namenodes.Clients will first try one of the NNs > (non-deterministically) and if its a standby NN, then it will respond to the > client to retry the request on the other Namenode. > If the client happens to talks to the Standby first, and the standby is > undergoing some GC / is busy, then those clients might not get a response > soon enough to try the other NN. > Proposed Approach to solve this : > 1) Since Zookeeper is already used as the failover controller, the clients > could talk to ZK and find out which is the active namenode before contacting > it. > 2) Long-lived DFSClients would have a ZK watch configured which fires when > there is a failover so they do not have to query ZK everytime to find out the > active NN > 2) Clients can also cache the last active NN in the user's home directory > (~/.lastNN) so that short-lived clients can try that Namenode first before > querying ZK -- This message was sent by Atlassian JIRA (v6.3.4#6332)