feat: Add least (weighted) connections load balancing#821
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simbiont666 wants to merge 3 commits intocloudflare:mainfrom
Open
feat: Add least (weighted) connections load balancing#821simbiont666 wants to merge 3 commits intocloudflare:mainfrom
simbiont666 wants to merge 3 commits intocloudflare:mainfrom
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simbiont666
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Feb 19, 2026
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| // We pass the state store least connections through config so that | ||
| // when the selector is rebuilt, counters for unchanged backends can be reused | ||
| let mut upstreams = LoadBalancer::<LeastConnections>::from_backends_with_config( | ||
| Backends::new(discovery::Static::try_from_iter(["1.1.1.1:443", "1.0.0.1:443"]).unwrap()), | ||
| Some(LeastConnectionsConfig::new()), | ||
| ); |
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i'm not sure whether I should keep the part about creating a LoadBalancer with config
for now, I removed it so the example focuses on working with lease and CTX
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closes #144
Hi! This is my attempt at implementing a least (weighted) connections selection algorithm.
What's here
New API on LoadBalancer
I added
select_with_lease()and select_with_lease_with()methods specifically for theLeastConnectionsselector. They work just likeselect()/select_with(), but return a(Backend, LeastConnLease)tuple. The lease should be held for the entire duration of the proxied request - in practice this means storing it inCTXstruct and letting it drop naturally when the request completes.State preservation across rebuilds
This was the trickiest part and the exact issue raised in #269 (2)- when
LoadBalancer::update()rebuilds the selector, inflight counters must survive. The solution isLeastConnStateStore, which lives insideLeastConnectionsConfigand maps backend hashes toWeak<AtomicU32>. On rebuild,Weak::upgrade()recovers any counter that still has live references (active leases or the previous selector), so inflight counts carry over seamlessly. If you don't need state persistence across updates (static backends), the defaultbuild()path works out of the box with no extra config.Notes
Let me know if anything looks off or could be done better. Thanks!