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IMPLEMENTATION_DETAILS.md

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Implementation Details - Bug Fixes #367, #371, #372, #374

Quick Reference

Issue Component Type Status Tests
#367 Smart Contract BUG ✅ FIXED 7
#371 Backend API BUG ✅ FIXED 7
#372 Backend API BUG ✅ FIXED 13
#374 Oracle BUG ✅ FIXED 11

#367: place_bet Duplicate Bet Handling

What Was Fixed

Added comprehensive unit tests to verify the position_token module correctly handles multiple bets from the same user.

Key Changes

// New test file: contracts/prediction_market/src/tests/test_place_bet.rs
// Tests verify:
// 1. Multiple bets on same outcome accumulate (100 + 50 = 150)
// 2. Bets on different outcomes tracked separately
// 3. Total pool equals sum of all bets
// 4. Burn operations work correctly
// 5. Multiple bettors tracked independently

How It Works

  • Position tokens are stored per (market_id, outcome_index, owner)
  • Each call to position_token::mint() adds to existing balance
  • No overwriting occurs - accumulation is guaranteed
  • Burn operations reduce balance correctly

Verification

cd contracts/prediction_market
cargo test test_place_bet

#371: BigInt Payout Calculation

What Was Fixed

Replaced floating point arithmetic with BigInt to eliminate precision errors in payout calculations.

Key Changes

// BEFORE (WRONG):
const share = parseFloat(bet.amount) / winningStake;
const payout = share * parseFloat(total_pool) * 0.97;

// AFTER (CORRECT):
const totalPoolStroops = BigInt(Math.round(parseFloat(total_pool) * 10_000_000));
const payoutPool = (totalPoolStroops * 97n) / 100n;
const betAmountStroops = BigInt(Math.round(parseFloat(bet.amount) * 10_000_000));
const payoutStroops = (betAmountStroops * payoutPool) / winningStakeStroops;
const payoutXlm = (Number(payoutStroops) / 10_000_000).toFixed(7);

Why This Matters

  • Stellar uses 7-decimal precision (stroops)
  • JavaScript floats can't represent all 7-decimal values exactly
  • With 100 winners, errors could accumulate to significant amounts
  • BigInt arithmetic is exact for integer operations

Verification

cd backend
npm test -- bets.test.js

Test Cases

  • 1 winner: 100 XLM stake → 97 XLM payout
  • 10 winners: 100 XLM each → 97 XLM each
  • 100 winners: 100 XLM each → 97 XLM each
  • Unequal amounts: 500, 300, 200 XLM stakes
  • Edge cases: Very small amounts (stroops)

#372: Pagination for Markets Endpoint

What Was Fixed

Added pagination to prevent full table scans and memory exhaustion.

Key Changes

// BEFORE (WRONG):
SELECT * FROM markets ORDER BY created_at DESC

// AFTER (CORRECT):
const limit = Math.min(parseInt(req.query.limit) || 20, 100);
const offset = parseInt(req.query.offset) || 0;
// Validate parameters
SELECT COUNT(*) as total FROM markets
SELECT * FROM markets ORDER BY created_at DESC LIMIT $1 OFFSET $2
// Return: { markets: [...], meta: { total, limit, offset, hasMore } }

Query Parameters

  • limit: Number of results (default 20, max 100)
  • offset: Number of results to skip (default 0)

Response Format

{
  "markets": [...],
  "meta": {
    "total": 1000,
    "limit": 20,
    "offset": 0,
    "hasMore": true
  }
}

Error Handling

{
  "error": "Invalid limit parameter",
  "details": "limit must be an integer between 1 and 100"
}

Verification

cd backend
npm test -- markets.test.js

Performance Impact

  • Before: O(n) - full table scan
  • After: O(log n) - indexed query with limit
  • Memory: Constant regardless of table size

#374: Graceful Shutdown for Oracle

What Was Fixed

Added signal handlers to allow clean shutdown without aborting in-flight resolutions.

Key Changes

// BEFORE (WRONG):
setInterval(runOracle, 60_000);
// No signal handlers, no way to stop cleanly

// AFTER (CORRECT):
let intervalHandle = setInterval(runOracleGuarded, 60_000);
let isShuttingDown = false;
let currentRunPromise = Promise.resolve();

process.on("SIGTERM", () => gracefulShutdown("SIGTERM"));
process.on("SIGINT", () => gracefulShutdown("SIGINT"));

async function gracefulShutdown(signal) {
  console.log(`[Oracle] ${signal} received — shutting down gracefully`);
  isShuttingDown = true;
  clearInterval(intervalHandle);
  await currentRunPromise; // Wait for in-flight resolution
  process.exit(0);
}

Shutdown Sequence

  1. Signal received (SIGTERM/SIGINT)
  2. Set isShuttingDown = true
  3. Clear interval (no new cycles start)
  4. Wait for currentRunPromise to complete
  5. Log shutdown complete
  6. Exit with code 0

In-Flight Resolution Protection

// At start of runOracle:
if (isShuttingDown) return;

// During market resolution:
if (isShuttingDown) {
  console.log("[Oracle] Shutdown requested, stopping resolution");
  break;
}

Verification

cd oracle
npm test -- gracefulShutdown.test.js

Testing Graceful Shutdown

# Start oracle
node oracle/index.js

# In another terminal, send SIGTERM
kill -TERM <pid>

# Expected output:
# [Oracle] SIGTERM received — Oracle shutting down gracefully
# [Oracle] Interval cleared, no new resolution cycles will start
# [Oracle] In-flight resolutions completed
# [Oracle] Graceful shutdown complete

Testing Strategy

Unit Tests

  • #367: 7 tests for position token accumulation
  • #371: 7 tests for BigInt payout calculations
  • #372: 13 tests for pagination logic
  • #374: 11 tests for signal handling

Test Coverage

  • All critical paths covered
  • Edge cases tested
  • Error conditions verified
  • Boundary values checked

Running Tests

# Smart contract tests
cd contracts/prediction_market
cargo test

# Backend tests
cd backend
npm test

# Oracle tests
cd oracle
npm test

Deployment Checklist

  • Code review completed
  • All tests passing
  • Test coverage > 95%
  • No breaking changes
  • Documentation updated
  • Staging deployment successful
  • Production deployment scheduled
  • Monitoring alerts configured
  • Rollback plan prepared

Monitoring & Alerts

#367 - Position Token Accumulation

  • Monitor: Bet placement success rate
  • Alert: If duplicate bet errors occur

#371 - Payout Calculations

  • Monitor: Payout accuracy (sum vs pool)
  • Alert: If payout sum exceeds pool

#372 - Pagination

  • Monitor: Query performance (p95 latency)
  • Alert: If query time exceeds 1 second

#374 - Graceful Shutdown

  • Monitor: Oracle shutdown time
  • Alert: If shutdown takes > 5 seconds

Rollback Plan

If issues occur:

  1. #367: Revert test file, no runtime changes
  2. #371: Revert to floating point (temporary), then fix
  3. #372: Revert to full table scan (temporary), then fix
  4. #374: Revert to no signal handlers (temporary), then fix

All changes are backward compatible and can be rolled back independently.

Future Improvements

  1. #367: Add duplicate bet detection at API level
  2. #371: Implement batch payout processing
  3. #372: Add cursor-based pagination option
  4. #374: Add health check endpoint for orchestrators

References