perf(sdk): reuse connections via sticky address rotation - #4545
perf(sdk): reuse connections via sticky address rotation#4545PastaPastaPasta wants to merge 3 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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✅ Final review complete — no blockers (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.
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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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Final validation — GLM Flash + Sol
The connection-key narrowing and basic sticky rotation are sound, but four in-scope issues remain: oversized base periods still panic and poison the address list, recently removed rotation members can immediately return, whole-list mode performs unnecessary quadratic scans, and a WASM comment misstates the pool-key behavior. These are client-side, non-consensus issues, so they are suggestions or a nitpick under the project severity policy.
Source: reviewer 1: glm-5.3-flash (agent: phase1-reviewer, role: general); reviewer 2: glm-5.3-flash (agent: phase1-reviewer, role: rust-quality); reviewer 3: gpt-5.6-sol (agent: phase2-reviewer, role: general); reviewer 4: gpt-5.6-sol (agent: phase2-reviewer, role: rust-quality); final verifier: gpt-5.6-sol (agent: sol-verifier, role: final-verifier)
Review provenance
- Phase 1 reviewers (GLM Flash):
glm-5.3-flash— general (completed); agentphase1-reviewer,glm-5.3-flash— rust-quality (completed); agentphase1-reviewer - Fresh verifier (Sol):
gpt-5.6-sol— final-verifier; agentsol-verifier - Phase 2 reviewers (Sol):
gpt-5.6-sol— general (completed); agentphase2-reviewer,gpt-5.6-sol— rust-quality (completed); agentphase2-reviewer
🟡 3 suggestion(s) | 💬 1 nitpick(s)
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These findings are from an automated code review. Verify each finding against the current code and only fix it if needed.
In `packages/rs-dapi-client/src/address_list.rs`:
- [SUGGESTION] packages/rs-dapi-client/src/address_list.rs:127: Oversized base ban periods bypass the 24-hour safety cap
`MAX_BAN_PERIOD.max(*base_ban_period)` raises the purported cap whenever the publicly configurable base period exceeds 24 hours. For example, `AddressList::with_settings(Duration::MAX).ban(...)` selects `Duration::MAX` as the ban period. Chrono 0.4.44's `Add<std::time::Duration>` implementation then calls `TimeDelta::from_std(rhs).expect(...)`, which panics for that value. Because this occurs while `AddressList::ban_with_reason` holds the addresses write lock, the panic also poisons the shared list. Use the unconditional 24-hour cap and update the documentation and regression test to cover an oversized configured base period.
- [SUGGESTION] packages/rs-dapi-client/src/address_list.rs:443-449: Recently evicted or expired addresses can immediately re-enter rotation
The promotion filter excludes only addresses still present in `rotation.active`. An address removed by `evict_from_rotation`, or removed because its slot expired, remains live in the address map and is immediately eligible to refill the vacancy it created. With `active_set_size(1)` and two live nodes, the failed node has a 50% chance of being selected again on the next retry despite an available standby; with larger sets it can immediately regain a slot and resume receiving traffic shortly afterward. This undermines failover when `ban_failed_address` is false and allows an expired member to replace itself instead of rotating to a true standby. Preserve just-removed addresses as refill exclusions, falling back to them only when no alternative live address exists, and add a single-slot failover regression test.
- [SUGGESTION] packages/rs-dapi-client/src/address_list.rs:439: Whole-list mode rescans the full active set on every request
When `active_set_size` exceeds the list length, particularly for the documented `usize::MAX` opt-out, `size.saturating_sub(rotation.active.len())` remains large after every address is already active. Clamping that value to `guard.len()` therefore reports `guard.len()` vacancies rather than zero. Every subsequent request scans the map and compares each entry against the full active vector, producing O(n²) work and an unnecessary candidate allocation when there is nothing to promote. Bound the vacancy count by the number of map entries outside the active set.
In `packages/rs-dapi-client/src/request_settings.rs`:
- [NITPICK] packages/rs-dapi-client/src/request_settings.rs:140-142: Comment overstates what cannot split the WASM pool key
The WASM channel builder ignores its settings argument, but `max_decoding_message_size` still correctly participates in the key because `transport/grpc.rs` applies it to the generated client after channel construction. Saying that the transport ignores all settings and that nothing may split the key could lead a future maintainer to incorrectly remove the decoding limit. Limit the comment to `connect_timeout` and the channel builder.
3 participants
Issue being fixed or feature implemented
Randomly choosing a DAPI node for every attempt spreads requests across cold hosts and repeatedly pays TCP/TLS setup costs. Per-request settings also split the native connection pool even when the underlying transport settings are identical.
What was done?
AddressList::with_active_set_sizeconfigures all clones;usize::MAXopts into whole-list round-robin selection without oversized allocations or redundant refill scans once full.The latest review fixes are in
4233c69f2a: standby preference, unconditional ban cap, whole-list vacancy calculation, and the WASM comment. Tests now check selection after eviction, standby replacement after expiry, fallback with insufficient standbys, oversized base periods, and executor retry with banning disabled.Scope for final review: configuration remains client-level through
AddressList(usable withSdkBuilder::with_address_list). A dedicated WASM/JS settings surface is deferred; per-request settings would conflict over shared rotation. The address-based cursor preserves ordering through eviction, and ban state remains centralized in the address map. NoArc<Address>API refactor is included.How Has This Been Tested?
Locally on macOS at
4233c69f2a:cargo test -p rs-dapi-client --locked --offline: 144 passed.cargo test -p rs-dapi-client --all-features --locked --offline: 151 passed.cargo clippy -p rs-dapi-client --all-features --all-targets --locked --offline -- --no-deps -D warnings: passed.cargo check -p dash-sdk --locked --offline: passed; reports an existing unused import in untouched Drive code.cargo check -p rs-dapi-client --target wasm32-unknown-unknown --locked --offline: passed.cargo fmt --all --checkandgit diff --check: passed.The strengthened tests reproduced five failures before the fixes. The executor regression uses a scripted transport, without network access. Code-review-validator and code-simplifier passes found no remaining blocking issue in the focused changes.
The earlier native testnet benchmark reported about 1.5× faster sequential queries. It predates these review fixes; no new browser or network benchmark is claimed.
Rust workspace CI is skipped for this fork by repository policy. The local checks above are the validation evidence; a full workspace CI pass is not claimed.
Breaking Changes
No API signatures removed or changed. Address selection now uses sticky rotation, and ban windows are capped at 24 hours even for larger configured base periods.
Checklist:
For repository code-owners and collaborators only
Summary by CodeRabbit
New Features
Performance
Bug Fixes