perf(sdk): reuse connections via sticky address rotation - #4545
perf(sdk): reuse connections via sticky address rotation#4545PastaPastaPasta wants to merge 2 commits into
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Address selection previously picked a uniformly random DAPI node from the full list (~259 hosts on mainnet) on every request attempt, so nearly every request landed on a cold host and paid a fresh TCP + TLS handshake, defeating the connection pool entirely (and, on WASM, the browser's per-origin connection reuse). AddressList now rotates round-robin over a small sticky active set (default 5, configurable via with_active_set_size). Banned or removed addresses are pruned from the set on the next selection and random live standby addresses are promoted in their place, so the existing ban ladder remains the only health signal and failover behavior is unchanged. The connection pool key now covers only connection-affecting settings (connect timeout, decode limit, CA certificate) instead of the whole applied-settings debug string, so requests differing only in per-request knobs (timeout, retries, banning) share one channel per host - e.g. broadcastStateTransition and waitForStateTransitionResult no longer handshake separately. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
📝 WalkthroughWalkthroughChangesAddress rotation
Connection pool keys
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🔵 Low · up to Cloned clients can ignore a smaller configured active-set size and use more nodes than intended, causing bounded connection-reuse and performance behavior differences. The PR is otherwise mergeable with explicit owner awareness or follow-up for this localized issue. Suggested reviewers: Sequence Diagram(s)sequenceDiagram
participant Caller
participant AddressList
participant Rotation
participant AddressStatus
Caller->>AddressList: get_live_address
AddressList->>AddressStatus: is_live
AddressList->>Rotation: prune active addresses
AddressList->>Rotation: promote live standbys
Rotation-->>AddressList: next round-robin address
AddressList-->>Caller: selected address
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Full details: Docstring CoverageExplanation Docstring coverage is 93.10% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 29 functions across 3 files. (1 skipped: 1 unsupported.) ✨ Finishing Touches🧪 Generate unit tests (beta)
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🕓 Ready for review — 4 ahead in queue (commit 155fc49) |
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Actionable comments posted: 1
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Inline comments:
In `@packages/rs-dapi-client/src/address_list.rs`:
- Line 368: Update the rotation handling around AddressList and its shared
rotation state so each clone enforces its own active_set_size before computing
vacancies; trim excess rotation.active entries first, then calculate vacancies,
preserving the configured limit during subsequent rotations.
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📒 Files selected for processing (4)
packages/rs-dapi-client/Cargo.tomlpackages/rs-dapi-client/src/address_list.rspackages/rs-dapi-client/src/connection_pool.rspackages/rs-dapi-client/src/request_settings.rs
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Benchmark: 100 testnet queries, with vs. without this PRMethodology: 100 sequential queries per run against the full testnet evonode address list (30 hosts), mimicking a yappr browsing session —
Reading the numbers:
🤖 Posted autonomously by Claude on behalf of pasta. |
| addresses: Arc::new(RwLock::new(HashMap::new())), | ||
| rotation: Arc::new(RwLock::new(Rotation::default())), | ||
| base_ban_period, | ||
| active_set_size: DEFAULT_ACTIVE_SET_SIZE, |
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should be configurable, maybe with RequestSettings, with an option to opt out (use all nodes available)
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Two parts of this are now in place as of 155fc49:
- Opt-out: promotion is clamped to the live-address count, so
with_active_set_size(usize::MAX)now safely rotates round-robin over the whole list (documented on the method). The size also moved into the shared rotation state, so it applies consistently across clones and shrinking trims the set. - Slot lifetime: each slot expires after a jittered 5–7.5 min, so stickiness is bounded regardless of configuration.
On RequestSettings specifically: the rotation is client-level shared state while RequestSettings is per-request/per-request-type, so two request types with different values would fight over one rotation (last caller wins). A client/builder-level knob (SdkBuilder, wasm-sdk settings) seems like the right surface — the PR body lists that as a follow-up; happy to do it in a separate PR if you agree.
🤖 Posted autonomously by Claude on behalf of pasta.
| let last_position = rotation | ||
| .last_served | ||
| .as_ref() | ||
| .and_then(|last| rotation.active.iter().position(|address| address == last)); |
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doesn't look like the best solution performance-wise.
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The scan is O(active_set_size) over a Vec of ≤ 5 entries — a handful of pointer-sized compares (http::Uri equality on interned parts), tens of nanoseconds against a code path whose whole purpose is to precede a network round trip. The alternative (a stored index) is what an earlier revision used, and it double-serves an address after an eviction re-orders the set — test_get_live_address_no_immediate_repeat_after_other_member_evicted pins that regression.
Since 155fc49 the SmallRng::from_entropy() OS-entropy call was also moved out of the write-lock critical section, which was the only real per-call cost in here. If active sets ever grow beyond a handful of members, swapping the scan for a smarter cursor is easy — but at ≤ 5 members it would be complexity without a measurable win.
🤖 Posted autonomously by Claude on behalf of pasta.
| #[derive(Debug, Default)] | ||
| struct Rotation { | ||
| active: Vec<Address>, | ||
| last_served: Option<Address>, |
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maybe store index instead (and ignore issues when new item is added/removed)?
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An index-based cursor was actually the first cut here, and it has a subtle bug: when a member other than the just-served one is evicted, the indices shift and the same address can be served twice in a row (or a just-promoted one skipped). "Ignore issues when an item is added/removed" is exactly the case the rotation exists to handle — eviction + promotion is the failover path, so churn is when correctness matters most. test_get_live_address_no_immediate_repeat_after_other_member_evicted pins this. With ≤ 5 members the address-equality lookup costs the same as an index bounds-check in practice.
🤖 Posted autonomously by Claude on behalf of pasta.
| /// most recently served one that round-robin selection advances from. | ||
| #[derive(Debug, Default)] | ||
| struct Rotation { | ||
| active: Vec<Address>, |
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I guess we should have Arc
or sth like that, to only have one instance of address and reflect ban status etc. correctly.There was a problem hiding this comment.
Ban status only ever lives in the addresses map — the rotation stores addresses purely as keys, and get_live_address re-validates every member against the map (status.is_live) on each selection before serving it. So there's no second copy of ban state to drift; a ban through any handle takes effect on the very next selection. What is duplicated is the Address/Uri value itself, and cloning that is cheap (http::Uri is built on ref-counted Bytes).
Agreed Arc<Address> would be a nice tidy-up to deduplicate the values themselves, but it touches the public AddressList iteration/API surface, so I'd rather do it as a follow-up than fold it into this PR.
🤖 Posted autonomously by Claude on behalf of pasta.
Active-set slots now expire after a jittered 5-7.5 minute lifetime, so no small set of nodes observes a client's whole query stream for the process lifetime while connections still stay warm for minutes at a time. Failover no longer depends on the ban ladder: when banning is disabled (ban_failed_address=false, e.g. FFI token operations), a failing node is evicted from the rotation without touching its ban state, instead of keeping its slot forever. The exponential ban ladder and server-advertised ban windows are capped at 24h, closing a DateTime overflow panic (reachable around ban_count 26) that poisoned the shared address-list lock. Also: active_set_size moved into the shared rotation state so all clones agree (and shrinking now trims the set); promotion count clamped to the list length so an oversized value cannot over-allocate; RNG seeded outside the rotation write lock so an entropy failure cannot poison it; pool key embeds full CA certificate bytes instead of a 64-bit non-cryptographic hash; connection_key narrowed to pub(crate) with exhaustive destructuring; connect_timeout excluded from the wasm pool key (wasm transport ignores it); pool key settings segment always present so the two branches cannot collide.
PastaPastaPasta
changed the title
Review feedback triage → 155fc49An external code-review report (24 findings) plus the inline review comments were each verified against the code rather than taken at face value. Outcome: Fixed in 155fc49
Assessed, not changed (with reasons)
Verification (Rust CI does not run for this fork PR — fork guard in
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Issue being fixed or feature implemented
The evo-sdk (and every consumer of
rs-dapi-client) feels much slower than needed because address selection picked a uniformly random DAPI node from the full list on every request attempt (~259 usable evonodes on mainnet after seed filtering). Virtually every request landed on a cold host and paid a fresh TCP + TLS handshake:ConnectionPoolcaches lazy tonic HTTP/2 channels per host, but a warm host is re-picked with probability < 1%, so the cache almost never hit a warm connection.fetch, where connection reuse belongs entirely to the browser's / Node's per-origin pool — useless when the origin changes on every request. HTTPS session caching never got a chance.Additionally, the pool cache key embedded
{:?}of the whole applied settings, so request types with per-request overrides split channels to the same host — e.g.broadcastStateTransition(default settings) andwaitForStateTransitionResult(30 s timeout override) each did their own handshake in the latency-critical state-transition flow.What was done?
AddressListnow keeps a small sticky active set (default 5 addresses, configurable viawith_active_set_size, minimum 1) and serves requests round-robin from it, advancing from the last-served address. The rest of the list is failover standby.ban_failed_address: false, e.g. the FFI token operations), a failing node is instead evicted from the rotation (evict_from_rotation) without touching its ban state, so failover works on that path too. Different SDK instances still randomize which addresses they stick to, preserving network-wide load spreading.DateTime + Durationoverflow panic (reachable aroundban_count26) that poisoned the shared address-list lock. The active-set size lives in the shared rotation state, so it applies consistently across clones, and shrinking it trims the set.ConnectionPoolkey now covers only connection-affecting settings (connect_timeout,max_decoding_message_size, CA certificate) via a crate-internalAppliedRequestSettings::connection_key(); per-request knobs (timeout,retries,ban_failed_address) no longer split otherwise-identical connections. The CA certificate contributes its full bytes (not a 64-bit hash),connect_timeoutis excluded on wasm32 where the transport ignores it, and the key is assembled with an exhaustive destructure so a future settings field cannot be silently omitted.allocfeature to theranddependency (required forIteratorRandom::choose_multipleunderdefault-features = false).Out of scope, noted for follow-up:
EvoNode::execute_transportdeliberately builds a throwaway single-slot pool per call (probing a specific node wants a fresh connection); exposing the active-set size through wasm-sdk/js-evo-sdk settings.How Has This Been Tested?
update_address_ban_status), shared active-set size across clones with shrink,usize::MAXset size rotating the whole list without over-allocating, and the 24 h caps on both ban paths.cargo test -p rs-dapi-client: 140 tests green, including the pre-existingunimplemented_failoverandrate_limit_banintegration suites.cargo clippy -p rs-dapi-client --all-features --all-targetsandcargo fmt --check: clean.cargo check -p rs-dapi-client --target wasm32-unknown-unknownandcargo check -p dash-sdk: build.Breaking Changes
None. Public API is additive (
with_active_set_size,evict_from_rotation);get_live_address()keeps its signature and liveness semantics, only the selection policy changed.Checklist:
For repository code-owners and collaborators only
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Summary by CodeRabbit
New Features
Performance
Bug Fixes