卡桑德拉不均匀的分区和热点 [英] Cassandra uneven partitions and hotspots

问题描述

我对Cassandra中的分区分布有疑问。

I have one doubt regarding partition distribution in Cassandra.

我的问题是我的分区大小不均，某些分区的访问权限比其他分区大，所以恐怕迟早会在某些分区中出现热点。

My problem is that my partitions are not even-sized, and some of the partitions are more accessed than others, so I'm afraid I'll have a hot spot in some partitions sooner or later.

例如：

1. 我有两个分区：A和B。


2. A的大小为10，B的大小为5。


3. 读取完整的A分区是我读取B的两倍。


4. 具有三个（1、2和3）节点，复制因子为2。

1. I've two partitions: A and B.
2. Size of A is 10, size of B is 5.
3. read the full A partition twice the times I read B.
4. have three (1, 2, and 3) nodes, with replication factor 2.

结果：

• 节点1（A）节点2（B ，A）节点3（B）


• 节点1的大小为10，读取1.0


• 节点2的大小为15，读取1.5


• 节点3的大小为5，读取0.5

• Node 1 (A) Node 2 (B, A) Node 3 (B)
• Node 1 size is 10, read 1.0
• Node 2 size is 15, read 1.5
• Node 3 size is 5, read 0.5

我的节点1和2超载。

我开始研究我的问题，我发现了虚拟节点的概念，但是我不太确定它的实际含义。

I started researching about my problem, and I found the Virtual Nodes concept, but I'm not too sure about what it actually means.

将单个分区键分配给不同的虚拟节点（1个分区键-> n个令牌范围）吗？

Will a single partition key be assigned to different virtual nodes (1 partition key -> n token ranges)?

一个分区键只能存储在一个虚拟节点？

One partition key can only be stored in a virtual node?

我必须对密钥进行分区，添加一些分区信息（例如随机％10或类似的东西），或者有一种方法可以让Cassandra自动执行此操作？ p>

I have to partition my keys adding some partition info (like a random % 10 or something) or there's a way to make Cassandra do it automatically?

推荐答案

将单个分区键分配给不同的虚拟节点（1>分区键-> n令牌范围）？

Will a single partition key be assigned to different virtual nodes (1 >partition key -> n token ranges)?

否。每个分区密钥将仅映射到一个虚拟节点及其副本。

No. Each partition key will be mapped to only one virtual node and it's replicas.

为避免出现热点，在此分区上添加分片密钥（随机数％n）很有用。分区键。否则，请尝试选择分区键，使其不会引起热点。

To avoid hotspots, it is useful to add a sharding key (random number % n) to the partition key. Otherwise try choosing your partition key such that it does not cause hotspots.

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