添加新节点后如何重新平衡Cassandra群集 [英] how to rebalance cassandra cluster after adding new node

问题描述

我有一个3节点的cassandra群集，其复制因子为2。这些节点运行的是dsc1.2.3或dsc1.2.4。每个节点的num_token值为256，并注释了initial_token。这3个节点的集群是完美平衡的，即每个集群拥有大约30％的数据。

I had a 3 node cassandra cluster with replication factor of 2. The nodes were running either dsc1.2.3 or dsc1.2.4. Each node had num_token value of 256 and initial_token was commented. This 3 node cluster was perfectly balanced i.e. each owned around 30% of the data.

其中一个节点崩溃了，所以我启动了一个新节点，nodetool删除了崩溃的节点。新节点已添加到集群中，但是两个较旧的节点现在拥有大部分数据（47.0％和52.3％），而新节点仅拥有0.7％的数据。

One of the nodes crashed so I started a new node and nodetool removed the node that had crashed. The new node got added to the cluster but the two older nodes have most of the data now (47.0% and 52.3%) and the new node has just 0.7% of the data.

nodetool状态的输出为

The output of nodetool status is

Datacenter: xx-xxxx
===================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--  Address           Load       Tokens  Owns   Host ID                               Rack
UN  10.xxx.xxx.xxx    649.78 MB  256     47.0%  ba3534b3-3d9f-4db7-844d-39a8f98618f1  1c
UN  10.xxx.xxx.xxx    643.11 MB  256     52.3%  562f7c3f-986a-4ba6-bfda-22a10e384960  1a
UN  10.xxx.xxx.xxx    6.84 MB    256     0.7%   5ba6aff7-79d2-4d62-b5b0-c5c67f1e1791  1c

我如何平衡该群集？

推荐答案

您没有提到在新节点上进行修复，如果确实尚未进行修复，则可能是新节点上缺少数据的原因。

You didn't mention running a repair on the new node, if indeed you haven't yet done that it's likely the cause of your lack of data on the new node.

在运行nodetool修复之前，新节点将仅保存写入其中的新数据或读取修复后的数据。如果我正确理解vnode，lly不需要重新平衡，但是我个人还没有使用vnode，所以我对此可能是错的。

Until you run a nodetool repair the new node will only hold the new data that gets written to it or the data that read-repair pulls in. With vnodes you generally shouldn't need to re-balance, if I'm understanding vnodes correctly, but I haven't personally yet moved to using vnodes so I may be wrong about that.

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