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Workload classification for merges and mutations #63211

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serxa opened this issue Apr 30, 2024 · 1 comment · May be fixed by #64061
Open

Workload classification for merges and mutations #63211

serxa opened this issue Apr 30, 2024 · 1 comment · May be fixed by #64061
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serxa commented Apr 30, 2024

There is a setting workload that allows to specify how a query should be classified for resource consumption (only IO resources at the moment). We need a way to specify the workload setting for merges and mutations.

Use case

  1. This will enable users to specify how queries and merges share IO. https://clickhouse.com/docs/en/operations/workload-scheduling#hierarchy.
  2. Setting different workload for different tables provides a way to prioritize merges of specific tables.
  3. Setting different workload for merges and mutations provides a way to prioritize one over another.

Describe the solution you'd like
Add a server and a merge tree settings merge_workload and mutation_workload.
@serxa serxa added the feature label Apr 30, 2024
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serxa commented May 1, 2024 •
edited

Also, we should pay attention to the existing scheduler of a background thread pool. We should avoid running tasks that are blocked by the IO scheduler, but occupy a thread in the background pool, blocking other tasks. It could lead to "priority inversion" of a kind.

@serxa serxa self-assigned this May 1, 2024
@serxa serxa linked a pull request May 17, 2024 that will close this issue
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Workload classification for merges and mutations ClickHouse/ClickHouse
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