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From: flier <git@git.apache.org>
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Subject: [GitHub] zookeeper pull request #180: ZOOKEEPER-2700 add JMX `takeSnapshot` method an...
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Message-Id: <20170221171422.408F3DFDD1@git1-us-west.apache.org>
Date: Tue, 21 Feb 2017 17:14:22 +0000 (UTC)
archived-at: Tue, 21 Feb 2017 17:14:24 -0000

Github user flier commented on a diff in the pull request:

    https://github.com/apache/zookeeper/pull/180#discussion_r102263924
  
    --- Diff: src/java/main/org/apache/zookeeper/server/ZooKeeperServer.java ---
    @@ -303,15 +305,38 @@ public void loadData() throws IOException, InterruptedException {
     
         public void takeSnapshot(){
    --- End diff --
    
    I have some scenes need to take snapshot, for example
    
    First, our major Zookeeper cluster was deployed in an AWS zone, some observers running at a dozen IDC. We use this topological structure because Zookeeper cluster is not friendly to multi-IDC deployment. Besize, our zookeeper snapshot and transaction logs are huge, because some wrong client usage that hard to fix in short time :(
    
    Sometimes, we plan to maintains the major cluster, we have to start another mirror cluster in same DC, and switch from the major cluster to the mirror cluster. If we do it faster enough, the observer and client will not concern the changes. That's why we need take snapshot to speed up the migration. If something got wrong, we could switch back to the old cluster, lost some transaction better than the whole system down.
    
    Second, our backup policy need a daily/hourly offline backup, to AWS S3 or other DC. I would like to take and upload a latest and clean snapshot, instead of tar an old snapshot with a number of transaction logs.
    
    Third, sometimes we need to deploy a new observer or a testing cluster in different DC, we have to copy the latest snapshot offline, because Zookeeper observer sync progress may become very slow, the TCP window could drop to 10-20KB/s in the 40-60% packet loss rate.


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