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From "Jay Zhuang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-14252) Use zero as default score in DynamicEndpointSnitch
Date Thu, 05 Jul 2018 17:12:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-14252?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16533909#comment-16533909
] 

Jay Zhuang commented on CASSANDRA-14252:
----------------------------------------

The change is reverted from 3.0 and 3.11 branches. More details: CASSANDRA-14555

> Use zero as default score in DynamicEndpointSnitch
> --------------------------------------------------
>
>                 Key: CASSANDRA-14252
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-14252
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Coordination
>            Reporter: Dikang Gu
>            Assignee: Dikang Gu
>            Priority: Major
>             Fix For: 4.0
>
>         Attachments: IMG_3180.jpg
>
>
> The problem I want to solve is that I found in our deployment, one slow but alive data
node can slow down the whole cluster, even caused timeout of our requests. 
> We are using DynamicEndpointSnitch, with badness_threshold 0.1. I expect the DynamicEndpointSnitch
switch to sortByProximityWithScore, if local data node latency is too high.
> I added some debug log, and figured out that in a lot of cases, the score from remote
data node was not populated, so the fallback to sortByProximityWithScore never happened.
That's why a single slow data node, can cause huge problems to the whole cluster.
> In this jira, I'd like to use zero as default score, so that we will get a chance to
try remote data node, if local one is slow. 
> I tested it in our test cluster, it improved the client latency in single slow data
node case significantly.  
> I flag this as a Bug, because it caused problems to our use cases multiple times.
>  ==== logs ===
> _2018-02-21_23:08:57.54145 WARN 23:08:57 [RPC-Thread:978]: sortByProximityWithBadness:
after sorting by proximity, addresses order change to [ip1, ip2], with scores [1.0]_
>  _2018-02-21_23:08:57.54319 WARN 23:08:57 [RPC-Thread:967]: sortByProximityWithBadness:
after sorting by proximity, addresses order change to [ip1, ip2], with scores [0.0]_
>  _2018-02-21_23:08:57.55111 WARN 23:08:57 [RPC-Thread:453]: sortByProximityWithBadness:
after sorting by proximity, addresses order change to [ip1, ip2], with scores [1.0]_
>  _2018-02-21_23:08:57.55687 WARN 23:08:57 [RPC-Thread:753]: sortByProximityWithBadness:
after sorting by proximity, addresses order change to [ip1, ip2], with scores [1.0]_
>  
>  
>  



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