CODEWITHSUNDEEP
cassandra
albertredneck
albertredneck

Reputation: 96

Cassandra uneven partitions and hotspots

I have one doubt regarding partition distribution in Cassandra.

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.

For example:

  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.

Results:

My nodes 1 and 2 are overloaded.

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

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

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

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?

Upvotes: 3

Views: 4021

Answers (1)

user2604706
user2604706

Reputation: 21

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

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

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.

Upvotes: 2

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