Limit to 3 pipelines per node per source #5792
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why 3? |
It's a ratio proposed by Paul here. The rational is that if you you start saturating the systems, merges being 3x faster than indexing, with this ratio merges would be able to keep up. |
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There are 2 issues with the logic so far:
EDIT: 2) is solved in #5808 |
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Actually this is wrong for now, I thought shards in the simplified problem were indexing pipelines in the physical plan, but it's not true. Shards in the simplified problem are physical shards, and they are mapped to pipelines in EDIT: solved now |
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rdettai
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Jun 12, 2025
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| // To ensure that merges can keep up, we try not to assign more than 3 | ||
| // pipelines per indexer for a source (except if there aren't enough nodes). | ||
| let target_limit_num_shards_per_indexer_per_source = | ||
| 3 * MAX_LOAD_PER_PIPELINE.cpu_millis() / source.load_per_shard.get(); |
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This is creating some undesired coupling with the rest of the code:
- we rely on convert_scheduling_solution_to_physical_plan to use the same MAX_LOAD_PER_PIPELINE to create the right amount of pipelines
- we rely on the default load_per_pipeline for non-ingest sources (e.g Kafka) to also use MAX_LOAD_PER_PIPELINE.
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Description
Closes #4470
Closes #5747
Closes #4630
This addresses both the limitation that only 1 merge pipelines can run per indexer at any given time and the fact that nodes systematically end up with all pipelines of a source when using Kafka, even if the number of pipelines for that source is rather large.
How was this PR tested?
Added unit test, should add more