feat(cbrs): load based routing strategy #7519
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onewland
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Nov 12, 2025
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| class LoadBasedRoutingStrategy(OutcomesBasedRoutingStrategy): | ||
| """ | ||
| If cluster load is under a threshold, ignore recommendations and allow the query to pass through with the tier decided based on outcomes-based routing. | ||
| """ |
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why is this inheriting from OutcomesBasedRoutingStrategy? shouldn't it inherit BaseRoutingStrategy?
I think it's mixing concerns weirdly to make the load-based routing in any way aware or coupled to outcomes-based routing. Some third entity/module should chain the two together if that's necessary.
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Originally the intention was to tightly couple load-based routing strategy with outcomes-based, but now thinking about it, it makes sense to separate the two, especially if in the future we want to use a different strategy to decide which tier. I used a new strategy to chain the two together
added 2 commits
December 2, 2025 13:55
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| def _update_routing_decision(self, routing_decision: RoutingDecision) -> None: | ||
| OutcomesBasedRoutingStrategy()._update_routing_decision(routing_decision) | ||
| LoadBasedRoutingStrategy()._update_routing_decision(routing_decision) |
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| if load_info is None: | ||
| return | ||
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| pass_through_threshold = int(self.get_config_value("pass_through_load_percentage")) | ||
| pass_through_max_threads = int(self.get_config_value("pass_through_max_threads")) | ||
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| if load_info.cluster_load < pass_through_threshold: |
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| def __init__(self) -> None: | ||
| self._outcomes_based_routing_strategy = OutcomesBasedRoutingStrategy() | ||
| self._load_based_routing_strategy = LoadBasedRoutingStrategy() |
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xurui-c
commented
Dec 4, 2025
| routing_decision: RoutingDecision, | ||
| ) -> None: | ||
| load_info = routing_decision.routing_context.cluster_load_info | ||
| if load_info is None or load_info.cluster_load < 0: |
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this means something in load retriever went wrong, in which case this would be as if only outcomes based routing strategy ran, which effectively means everything works the same as before
added 2 commits
December 3, 2025 16:53
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| def __init__(self) -> None: | ||
| self._outcomes_based_routing_strategy = OutcomesBasedRoutingStrategy() | ||
| self._load_based_routing_strategy = LoadBasedRoutingStrategy() |
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Basically does what
OutcomesBasedRoutingStrategydoes except when cluster load is low enough, we let the query through even if allocation policies say noRollout plan:
storage_routing_config_override={'{"1": {"version": 1, "config": {"LoadBasedOutcomesRoutingStrategy": 1.0}}}',default_storage_routing_config= '{"version": 1, "config": {"LoadBasedOutcomesRoutingStrategy": 0.5, "OutcomesBasedRoutingStrategy": 0.5}}'merging this PR does not automatically make any queries go through this routing strategy, I have to set the routing config in Snuba Admin