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High client connections on certain nodes due to uneven data distribution

Problem Description

If a node has more partitions than the other nodes in the cluster, this may cause it to have more client connections as well.

Explanation

By default, Aerospike optimizes the partition distribution across nodes in a cluster to minimize migration traffic (moving of partitions between the nodes when a node is added or removed from the cluster). The prefer-uniform-balance configuration forces a uniform distribution of partition at the expense of a bit more partition movement during migrations.

Solution

A cluster with unbalanced partition distribution being accessed uniformly across its records in general will have more traffic against the nodes holding more partitions (records) causing a correlated imbalance in client connection count. Enabling prefer-uniform-balance may help with this.

Other less common situations could lead into imbalanced data across nodes in a cluster. For example, a cluster that has received a restore job from a partial backup or that is currently getting data restored to it. Indeed, the backup process is a partition by partition scan, storing records on file in the order they are read. The restore process will therefore restore the records similarly, partition by partition, causing intermediate imbalance (or permanent if the backup was not full or if the restore was interrupted).


Applies To Earliest Version

Pre 4.9

Applies To Latest Version

Current Version
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