use current node load estimation when placing search jobs#6390
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PSeitz
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May 7, 2026
PSeitz
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May 11, 2026
| // Seed each candidate node with its current load so the placer avoids | ||
| // routing work to already-loaded nodes. If a node fails to report its | ||
| // load (error or timeout), `load` stays `None`: we still route work | ||
| // there if all other nodes are overloaded, but we prefer reachable |
Collaborator
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maybe we should error instead if all nodes are not reachable or overloaded
Platane
reviewed
May 22, 2026
PSeitz
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May 22, 2026
| const GET_LOAD_TIMEOUT: Duration = Duration::from_millis(200); | ||
| let load_futures = candidate_nodes.iter_mut().map(|node| { | ||
| let mut client = node.client.clone(); | ||
| async move { tokio::time::timeout(GET_LOAD_TIMEOUT, client.get_load()).await } |
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I wonder if we should have a 1 sec cache for the load to reduce traffic
PSeitz
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May 22, 2026
Mallets
reviewed
May 26, 2026
| self.total_job_cost.fetch_add(added, Ordering::Relaxed); | ||
| // fetch_add returns the previous value, so add `added` to get the new total. | ||
| let new_load = self.total_job_cost.fetch_add(added, Ordering::Relaxed) + added; | ||
| SEARCHER_NODE_LOAD.set(new_load as f64); |
Contributor
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nit: it seems that SEARCHER_NODE_LOAD stores the same value (1-to-1 mapping) of total_job_cost. SEARCHER_NODE_LOAD provides a get() method to retrieve the value if needed.
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i'm generally worried by global mutable state. imo it's okay to write to one for telemetry purpose, but i prefer not relying on it for any actual logic
PSeitz-dd
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May 26, 2026
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When placing jobs, first query all nodes for their current load, and bias placement toward less loaded nodes to even load on the cluster
this improves on a problem where some nodes might be overloaded while other are underloaded, causing queueing despite not all nodes being at max capacity
in testing, this was seen improving slightly p50+ under constant light load, and increased the max qps before latency explodes. Metrics also showed all searcher busy when some would be only part-time working before
future improvements: