Mailing-List: contact hdfs-issues-help@hadoop.apache.org; run by ezmlm
Precedence: bulk
Reply-To: hdfs-issues@hadoop.apache.org
Date: Mon, 27 Jul 2015 19:09:06 +0000 (UTC)
From: "Arun Suresh (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12778318.1425071097000.300071.1438024146036@Atlassian.JIRA>
In-Reply-To: <JIRA.12778318.1425071097000@Atlassian.JIRA>
References: <JIRA.12778318.1425071097000@Atlassian.JIRA>
 <JIRA.12778318.1425071097003@arcas>
Subject: [jira] [Updated] (HDFS-7858) Improve HA Namenode Failover detection
 on the client
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit


     [ https://issues.apache.org/jira/browse/HDFS-7858?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Arun Suresh updated HDFS-7858:
------------------------------
    Attachment: HDFS-7858.12.patch

Thanks for the rev [~arpitagarwal],

Updated patch :
* Incorporated your optimization with a minor modification (with consideration for case where you might have more than 2 proxies configured). Also updated 
* Updated docs
* Updated testcases

Will commit it by tomorrow, if you and [~jingzhao] are ok with the latest patch

> 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
>            Reporter: Arun Suresh
>            Assignee: Arun Suresh
>              Labels: BB2015-05-TBR
>         Attachments: HDFS-7858.1.patch, HDFS-7858.10.patch, HDFS-7858.10.patch, HDFS-7858.11.patch, HDFS-7858.12.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)