Pyroscope query-scheduler

{{< admonition type="note" >}} The query-scheduler is a v1 architecture component. In v2, the [query frontend]({{< relref "../../reference-pyroscope-v2-architecture/components/query-frontend" >}}) communicates directly with [query backends]({{< relref "../../reference-pyroscope-v2-architecture/components/query-backend" >}}) without an intermediary scheduler. {{< /admonition >}}

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:

1. The query-frontend receives queries, and then either splits and shards them, or serves them from the cache.
2. The query-frontend enqueues the queries into a query-scheduler.
3. The query-scheduler stores the queries in an in-memory queue where they wait for a querier to pick them up.
4. Queriers pick up the queries, and executes them.
5. 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.

Configuration

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.

Operational considerations

For high-availability, run two query-scheduler replicas.