The query-scheduler is a stateless component that retains a queue of queries to execute, and distributes the workload to available queriers.
The query-scheduler is a required component when using the query-frontend.
The following flow describes how a query moves through a Pyroscope cluster:
- The query-frontend receives queries, and then either splits and shards them, or serves them from the cache.
- The query-frontend enqueues the queries into a query-scheduler.
- The query-scheduler stores the queries in an in-memory queue where they wait for a querier to pick them up.
- Queriers pick up the queries, and executes them.
- The querier sends results back to query-frontend, which then forwards the results to the client.
Benefits of using the query-scheduler
Query-scheduler enables the scaling of query-frontends. To learn more, see Mimir Query Frontend documentation.
To use the query-scheduler, query-frontends and queriers need to discover the addresses of query-scheduler instances. To advertise itself, the query-scheduler uses Ring-based service discovery which is configured via the memberlist configuration.
For high-availability, run two query-scheduler replicas.