[SOLVED] prometheus-operator: what is the difference between shards and replicas?

prometheus-operator: what is the difference between shards and replicas?

The following manifest creates a Prometheus server with two replicas and two shards:

apiVersion: monitoring.coreos.com/v1
kind: Prometheus
metadata:
  labels:
    prometheus: prometheus
  name: prometheus
  namespace: default
spec:
  serviceAccountName: prometheus
  replicas: 2
  shards: 2
  serviceMonitorSelector:
    matchLabels:
      team: frontend

What is the difference between replicas and shards?

Solution

Sharding in Prometheus involves splitting the metrics across multiple servers, to improve performance (especially query performance) and scalability. Each shard is responsible for collecting and storing a subset of the total metrics.

Replication involves creating multiple copies of the data across multiple servers, to increase availability and fault tolerance. Each replica contains a full copy of the data, and any changes made to one replica are eventually propagated to the others.

This is true for any app - shard and replication are generic concepts used to describe this and not something specific to prometheus. This is widely used in Databases.