Rate Limiter Implementation - #262

Document status (2026-07-29): This file mixes an original implementation report with claims that are no longer accurate for the current tree. Sections marked ⚠️ STALE describe aspirational or outdated state. See Current implementation snapshot below before relying on setup or integration guidance.

Current implementation snapshot

Item	Actual state
Contract	`Contracts/src/RateLimiter.sol` — standalone `AccessControl` contract with per-limit windows, operator-gated `recordOperation`, and admin configuration
Forge tests in CI	`Contracts/test/*.sol` run via `cd Contracts && forge test` (see `Contracts/.github/workflows/test.yml`)
RateLimiter tests	⚠️ STALE path: `test/RateLimiter.t.sol` at repo root imports `../src/RateLimiter.sol` and is not part of the `Contracts/` Foundry project; treat as legacy/orphaned until moved to `Contracts/test/`
Trading / MarketMaker integration	Not wired — `Trading.sol` and `MarketMaker.sol` do not call `RateLimiter`
Backend rate limiting	Separate stack: Nest `Backend/src/rate-limiter/` and Express `Backend/middleware/rateLimiter.js` — not the on-chain contract
Production readiness	Contract code exists and is unit-testable in isolation; end-to-end enforcement is a Phase 4+ dependency (see Blocked / Phase dependencies)

✅ Implementation Complete (contract module)

The RateLimiter library contract was implemented with configurable limits, exemptions, and status queries. The bullets below remain accurate for the contract in isolation.

Files

1. RateLimiter.sol

Location: Contracts/src/RateLimiter.sol
Features:
- Multiple independent rate limits with unique IDs
- Configurable max operations and time windows
- Enable/disable limits without reconfiguration
- User-level exemptions for privileged users
- Automatic window reset after timeout
- Separate tracking per user per limit
- Detailed status and metrics queries

2. RateLimiter.t.sol — ⚠️ STALE location / CI path

Documented location: test/RateLimiter.t.sol (repository root)
CI / Foundry project: tests under Contracts/test/ are what forge test runs from Contracts/
Action for contributors: move or recreate coverage at Contracts/test/RateLimiter.t.sol before treating test counts below as CI-gated
Historical claim: 35+ test cases — applies to the root test/RateLimiter.t.sol file if compiled in a compatible Foundry layout (not verified in Contracts/ CI today)

Acceptance criteria (contract-only)

The following held for the original contract delivery. On-chain enforcement in Trading/MarketMaker is still outstanding.

1. Limit Operation Frequency ✅ (contract API)

configureRateLimit(limitId, maxOps, timeWindow, enabled) - Set limits
Automatic window reset after timeout
Operations blocked when limit exceeded (via recordOperation)

2. Track Operation Counts ✅

getOperationCount(limitId, user) - Current count in active window
getOperationStatus(limitId, user) - Full status object
Per-user, per-limit tracking
Automatic reset on window expiration

3. Enforce Rate Limits ✅ (when called)

checkRateLimit(limitId, user) - Returns boolean (allowed/blocked)
recordOperation(limitId, user) - Reverts if limit exceeded (OPERATOR_ROLE only)
recordOperationIfAllowed(limitId, user) - Returns boolean (OPERATOR_ROLE only)

4. Support Different Limits ✅

Multiple independent limits per system (e.g. LIMIT_TRADES, LIMIT_WITHDRAWALS)
Each limit has own max operations and time window

5. Provide Limit Queries ✅

getOperationCount(), getOperationStatus(), getTimeToNextWindow(), isRateLimited(), limitsExist(), getRateLimitConfig()

Core API

Configuration (Admin Only — `ADMIN_ROLE` / `DEFAULT_ADMIN_ROLE`)

configureRateLimit(bytes32 limitId, uint256 maxOps, uint256 timeWindow, bool enabled)
enableRateLimit(bytes32 limitId)
disableRateLimit(bytes32 limitId)

Rate Limiting (Operator — `OPERATOR_ROLE`)

checkRateLimit(bytes32 limitId, address user) → bool allowed
recordOperation(bytes32 limitId, address user) // reverts if limited
recordOperationIfAllowed(bytes32 limitId, address user) → bool allowed

Permission Control (Admin Only)

setLimitOverride(bytes32 limitId, address user, bool overridden)
isUserExempt(bytes32 limitId, address user) → bool

Status Queries (Anyone — public `view` functions)

getRateLimitConfig(bytes32 limitId) → (maxOps, timeWindow, enabled)
getOperationCount(bytes32 limitId, address user) → uint256 count
getOperationStatus(bytes32 limitId, address user) → (count, max, remaining, timeUntilReset, isLimited)
getTimeToNextWindow(bytes32 limitId, address user) → uint256 secondsUntilReset
isRateLimited(bytes32 limitId, address user) → bool
limitsExist(bytes32 limitId) → bool

Management (Admin Only)

resetUserLimits(bytes32 limitId, address user)

Key Features

(Documentation below describes contract behaviour — still accurate.)

Multiple Independent Limits

rateLimiter.configureRateLimit(LIMIT_TRADES, 100, 1 hours, true);
rateLimiter.configureRateLimit(LIMIT_WITHDRAWALS, 10, 24 hours, true);

Per-User Tracking

Each user has independent counters for each limit ID.

Automatic Window Reset

Windows expire after configured timeWindow; counters reset on the next qualifying operation.

User Exemptions

rateLimiter.setLimitOverride(LIMIT_TRADES, admin, true);

Enable/Disable Without Reconfiguration

rateLimiter.disableRateLimit(LIMIT_TRADES);
rateLimiter.enableRateLimit(LIMIT_TRADES);

Events

event RateLimitConfigured(bytes32 indexed limitId, uint256 maxOperations, uint256 timeWindow, bool enabled)
event OperationAllowed(bytes32 indexed limitId, address indexed user, uint256 operationCount)
event OperationBlocked(bytes32 indexed limitId, address indexed user, string reason)
event RateLimitReset(bytes32 indexed limitId, address indexed user)
event LimitOverrideSet(bytes32 indexed limitId, address indexed user, bool overridden)
event WindowRolled(bytes32 indexed limitId, address indexed user, uint256 newWindowStart)

Test coverage — ⚠️ STALE CI claims

Category	Historical claim	Current note
Configuration	6 tests	In root `test/RateLimiter.t.sol` only
Rate Limiting	6 tests	Not run by `Contracts/` CI until relocated
Overrides	3 tests
Status Queries	8 tests
Management	2 tests
Edge Cases	5 tests
TOTAL	35	⚠️ Not gating `Contracts` CI today

Architecture

Data Structures

RateLimitConfig - Per-limit configuration:

struct RateLimitConfig {
    uint256 maxOperations;
    uint256 timeWindow;
    bool enabled;
}

OperationTracker - Per-user-per-limit tracking:

struct OperationTracker {
    uint256 operationCount;
    uint256 windowStartTime;
    uint256 lastOperationTime;
}

Storage Model

rateLimitConfigs[limitId] → Configuration for limit
operationTrackers[limitId][user] → User's tracker for limit
userLimitOverrides[user][limitId] → Override flag

Usage examples (deploy + configure)

RateLimiter limiter = new RateLimiter();

limiter.configureRateLimit(
    keccak256("TRADES"),
    100,
    1 hours,
    true
);

Security features (contract)

✅ Role-Based Access Control — OpenZeppelin AccessControl (ADMIN_ROLE, OPERATOR_ROLE)

✅ Input Validation — positive maxOperations / timeWindow, non-zero limitId

✅ Safe Math — Solidity 0.8.20+ overflow checks

✅ No Reentrancy Risk — no external calls in limit updates

⚠️ STALE claim removed: “Users: Can only query their own status” — getOperationStatus and related getters are public and readable for any (limitId, user) pair (standard for on-chain counters).

Integration recommendations — ⚠️ STALE / not implemented

The snippets below are design targets, not current behaviour. Trading.sol, MarketMaker.sol, and withdrawal flows do not invoke RateLimiter yet.

Market Operations (planned)

// ⚠️ NOT WIRED — Phase 4 target (e.g. P4 on-chain RateLimiter in Trading)
function executeTrade(bytes calldata tradeData) external {
    rateLimiter.recordOperation(LIMIT_TRADES, msg.sender);
    // Execute trade...
}

Monitoring Dashboards (planned)

Off-chain indexers may call getOperationStatus today; product UI wiring is Phase 4+.

Blocked / Phase dependencies

Capability	Blocker	Phase
On-chain trade rate limits in `Trading` / `MarketMaker`	Contract not composed into trading path	Phase 4 (hardening)
CI-gated RateLimiter forge tests	Tests live under repo-root `test/`, outside `Contracts/` Foundry project	Phase 1 / 4 — relocate to `Contracts/test/`
Unified backend + on-chain limit story	Nest rate-limiter module ≠ Solidity `RateLimiter`	Phase 4
“Production ready” end-to-end	Requires deployment, role holders, and caller integration	Phase 4+

Local build / run

Green path for collaborators (see CONTRIBUTING.md):

cd Contracts && forge build && forge test
cd Backend && npm install && npm run start:dev
cd Frontend && npm install && npm run dev

No changes to contract logic are required for this documentation update.

Status: Contract implemented ✅ — product integration and CI test path ⚠️ incomplete (Phase 4+)

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