# Caching & Price Tracking Analysis - MEV Bot

**Date**: October 30, 2025
**Status**: ⚠️ CRITICAL ISSUES IDENTIFIED

---

## Executive Summary

Analysis of the MEV bot's caching and price tracking mechanisms reveals **3 critical issues** that are preventing effective arbitrage detection:

1. **Pool cache is NOT being persisted** to disk
2. **NO swap events are being processed** from the sequencer feed
3. **Prices are NOT being updated** from on-chain swaps

---

## 🔴 Critical Issue #1: Pool Cache Not Persisted

### Current Behavior

**Discovery IS working** ✅
- Bot discovered **96 pools** across 32 pairs (up from 10)
- All 20 new tokens found pools
- Discovery took ~3 minutes

**Cache NOT saved** ❌
- Pools stored in **memory only**
- `data/pools.json` shows old data (Oct 27 23:59)
- Discovered pools lost on restart

### Evidence

```bash
# Pool cache file (outdated)
-rw-r--r-- 1 administrator administrator 5.1K Oct 27 23:59 data/pools.json

# Current pools in cache
$ jq 'length' data/pools.json
10  # Should be 96!

# Latest discovery logs (17:59-18:00)
[INFO] ✅ Found 96 pools across 32 pairs
[INFO] Discovery complete! Monitoring 96 pools
```

### Root Cause

**Missing or not-called SaveCache function:**
- `poolsFile: "data/pools.json"` defined in discovery.go
- No evidence of SaveCache() being called after discovery
- Pools kept in memory but never persisted

### Impact

- **High**: Bot loses all discoveries on restart
- **High**: Must re-discover 96 pools every startup (3+ minutes)
- **Medium**: Increased RPC calls and startup time

---

## 🔴 Critical Issue #2: Zero Swap Events Processed

### Current Behavior

**Bot IS monitoring blocks** ✅
- Processing blocks every 3 seconds
- Checking for Uniswap V3 swap events
- Arbitrage service stats updating every 10s

**NO swaps detected** ❌
- 0 swap events found in 100+ blocks
- Every block shows: "NO SWAP EVENTS FOUND"
- 0 arbitrage opportunities detected

### Evidence

```bash
# Swap event count
$ grep "swap event" logs/mev_bot.log | wc -l
0  # Should be hundreds/thousands

# Block monitoring (17:13-17:14)
[INFO] 📦 Block 395116600: NO SWAP EVENTS FOUND
[INFO] 📦 Block 395116612: NO SWAP EVENTS FOUND
[INFO] 📦 Block 395116624: NO SWAP EVENTS FOUND
... (continues for all blocks)

# Arbitrage stats
[INFO] Arbitrage Service Stats - Detected: 0, Executed: 0
```

### Root Cause Analysis

**Possible causes:**
1. **Wrong event signature** - Uniswap V3 Swap signature mismatch
2. **Pool address filter** - Only monitoring 96 pools, swaps happening elsewhere
3. **Block processing lag** - Getting stale blocks after swaps already settled
4. **Log parsing error** - Swap logs exist but not being decoded correctly

### Expected Behavior

On Arbitrum mainnet:
- **~500-1000 swaps per minute** across all DEXes
- **~5-10 swaps per block** on monitored pools
- **Bot should detect 50+ swaps/minute** minimum

### Impact

- **CRITICAL**: Cannot detect arbitrage without swap data
- **CRITICAL**: No price updates = stale pricing
- **HIGH**: Bot is effectively blind to market activity

---

## 🔴 Critical Issue #3: No Price Updates

### Current Behavior

**Price tracking exists** ✅
- `ExchangePricer` with `priceCache` map
- `Market.UpdatePriceData()` function available
- Price cache initialized at startup

**Prices NOT being updated** ❌
- No swap events = no price data
- Pools have initial liquidity but no current prices
- Cache shows 0 entries

### Evidence

```bash
# Price-related logs
$ grep -i "price.*update" logs/mev_bot.log
(only gas price updates found, no token price updates)

# Price cache stats
priceCache: map[string]*PriceEntry  # Empty
cached_prices: 0

# Market price updates
$ grep "UpdatePriceData" logs/mev_bot.log
(no results)
```

### How Pricing SHOULD Work

```
1. Sequencer feed → New transaction
2. Decode Swap event → Extract amounts, pool
3. Calculate new price → sqrtPriceX96, tick
4. Update pool cache → Market.UpdatePriceData()
5. Compare prices → Detect arbitrage
```

### Current Broken Flow

```
1. Sequencer feed → New transaction ✅
2. Check for swaps → NONE FOUND ❌
3. No price calculation ❌
4. No cache update ❌
5. No arbitrage detection ❌
```

### Impact

- **CRITICAL**: Arbitrage detection requires real-time prices
- **HIGH**: Using stale/initial prices leads to false opportunities
- **HIGH**: Cannot react to market movements

---

## 📊 Token Cache Analysis

### Current State

```json
{
  "tokens_cached": 6,
  "expected": 20,
  "file": "data/tokens.json",
  "last_updated": "Oct 27 16:26"
}
```

### Issues

1. **Only 6 tokens cached** (should be 20)
2. **Missing new tokens**: PENDLE, RDNT, MAGIC, GRAIL, AAVE, CRV, BAL, COMP, MKR, USDC.e
3. **Stale data** - 3 days old

### Impact

- **MEDIUM**: Token metadata lookups may fail for new tokens
- **LOW**: Doesn't block trading, just missing metadata

---

## 🔍 Detailed Investigation

### Pool Discovery Process

**What's Working:**
```
✅ Discovery scans 190 pairs
✅ Finds pools via CREATE2 calculation
✅ Validates pools on-chain
✅ Stores pools in memory
✅ Logs discovery progress
```

**What's NOT Working:**
```
❌ SaveCache() not called after discovery
❌ data/pools.json not updated
❌ Pools lost on restart
```

### Swap Processing Pipeline

**What's Working:**
```
✅ Connects to Arbitrum sequencer feed
✅ Receives new blocks every 3 seconds
✅ Checks blocks for Uniswap V3 logs
✅ Monitors 96 pools
```

**What's NOT Working:**
```
❌ No swap events detected (0 in 1000+ blocks)
❌ No logs match Uniswap V3 Swap signature
❌ Either wrong signature OR pools inactive
```

### Price Caching System

**Components:**
- `ExchangePricer` - Manages cross-exchange pricing
- `PriceEntry` - Cache entry with timestamp & validity
- `Market.UpdatePriceData()` - Updates price per pool
- `priceCache` map - In-memory price storage

**Status:**
- ✅ System initialized
- ✅ Data structures ready
- ❌ Never receives swap data
- ❌ Never updates prices

---

## 🔧 Required Fixes

### Fix #1: Implement Pool Cache Persistence

**Add SaveCache call after discovery:**

```go
// In cmd/mev-bot/main.go after discovery complete
log.Info(fmt.Sprintf("🎉 Pool discovery complete! Monitoring %d pools", totalPools))

// ADD THIS: Save discovered pools to disk
if err := poolDiscovery.SaveCache(); err != nil {
    log.Error(fmt.Sprintf("Failed to save pool cache: %v", err))
} else {
    log.Info("✅ Pool cache saved to data/pools.json")
}
```

**Implement SaveCache if missing:**

```go
// In pkg/pools/discovery.go
func (pd *PoolDiscovery) SaveCache() error {
    pd.mu.RLock()
    defer pd.mu.RUnlock()

    // Convert map to slice
    pools := make([]*Pool, 0, len(pd.pools))
    for _, pool := range pd.pools {
        pools = append(pools, pool)
    }

    // Marshal to JSON
    data, err := json.MarshalIndent(pools, "", "  ")
    if err != nil {
        return fmt.Errorf("failed to marshal pools: %w", err)
    }

    // Write to file
    if err := os.WriteFile(pd.poolsFile, data, 0644); err != nil {
        return fmt.Errorf("failed to write pools file: %w", err)
    }

    return nil
}
```

### Fix #2: Debug Swap Event Detection

**Check event signature:**

```bash
# Uniswap V3 Swap event signature
keccak256("Swap(address,address,int256,int256,uint160,uint128,int24)")
= 0xc42079f94a6350d7e6235f29174924f928cc2ac818eb64fed8004e115fbcca67
```

**Add diagnostic logging:**

```go
// In swap processing
log.Info(fmt.Sprintf("Checking block %d for swaps", blockNumber))
log.Debug(fmt.Sprintf("Monitoring %d pools", len(monitoredPools)))

for i, log := range logs {
    log.Debug(fmt.Sprintf("Log %d: topics=%v", i, log.Topics))

    if log.Topics[0].Hex() == SwapEventSignature {
        log.Info("✅ SWAP FOUND!")
        // Process swap
    }
}
```

**Verify pool addresses:**

```go
// Check if we're monitoring the right pools
for pool := range monitoredPools {
    log.Debug(fmt.Sprintf("Monitoring pool: %s", pool.Hex()))
}
```

### Fix #3: Implement Price Updates from Swaps

**Add price update to swap handler:**

```go
// After processing swap event
func handleSwap(pool common.Address, sqrtPriceX96 *big.Int, tick int32) {
    // Calculate price from sqrtPriceX96
    price := uniswap.SqrtPriceX96ToPrice(sqrtPriceX96)

    // Update market data
    if market, exists := markets[pool]; exists {
        market.UpdatePriceData(price, liquidity, sqrtPriceX96, tick)
        log.Debug(fmt.Sprintf("Updated price for pool %s: %s",
            pool.Hex()[:8], price.String()))
    }

    // Update price cache
    cacheKey := fmt.Sprintf("%s/%s", tokenIn, tokenOut)
    priceCache[cacheKey] = &PriceEntry{
        Price:     price,
        Timestamp: time.Now(),
        Validity:  5 * time.Minute,
    }
}
```

---

## 🎯 Verification Steps

### After Fix #1 (Pool Persistence)

```bash
# 1. Start bot
./mev-bot start

# 2. Wait for discovery (3 minutes)
# Should see: "✅ Pool cache saved"

# 3. Check file updated
ls -lh data/pools.json
# Should show current timestamp

# 4. Verify contents
jq 'length' data/pools.json
# Should show 96 (not 10)

# 5. Restart bot
# Should load 96 pools instantly
```

### After Fix #2 (Swap Detection)

```bash
# Monitor logs for swaps
tail -f logs/mev_bot.log | grep -i swap

# Expected output:
[INFO] ✅ SWAP FOUND on pool 0x82af...
[INFO] Processing swap: 1000 USDC → 0.5 WETH
[INFO] Updated price for pool 0x82af
[INFO] Checking for arbitrage opportunities...
```

### After Fix #3 (Price Updates)

```bash
# Check price cache stats
grep "price.*cache\|cached.*price" logs/mev_bot.log

# Expected:
[INFO] Price cache stats: 32 prices cached
[INFO] Updated 15 prices in last minute
[INFO] Oldest price age: 45 seconds
```

---

## 📈 Expected Performance After Fixes

### Pool Management
- ✅ 96 pools persisted to disk
- ✅ Instant load on restart (<1 second)
- ✅ Discovery runs once, cache reused

### Swap Processing
- ✅ 50-100 swaps/minute detected
- ✅ Real-time price updates
- ✅ <100ms latency from swap to price update

### Arbitrage Detection
- ✅ Compare prices across 96 pools
- ✅ Detect opportunities within 1 block
- ✅ 5-10+ opportunities/hour expected

---

## 🚨 Priority Order

1. **URGENT**: Fix swap event detection (Fix #2)
   - **Why**: Bot is blind without swap data
   - **Impact**: Enables all arbitrage detection

2. **HIGH**: Implement price updates (Fix #3)
   - **Why**: Required for arbitrage calculation
   - **Impact**: Real-time opportunity detection

3. **MEDIUM**: Add pool cache persistence (Fix #1)
   - **Why**: Improves startup time
   - **Impact**: UX improvement, reduced RPC load

---

## 📝 Additional Recommendations

### Monitoring Enhancements

```bash
# Add metrics for debugging
- swap_events_processed (counter)
- price_updates_count (counter)
- cache_hit_rate (gauge)
- pool_count (gauge)
- arbitrage_opportunities_detected (counter)
```

### Logging Improvements

```go
// Add periodic stats logging
Every 60 seconds:
  - Pools monitored: 96
  - Swap events (last min): 47
  - Price updates (last min): 32
  - Arbitrage opportunities: 3
  - Cache size: 5.2KB
```

### Testing Strategy

1. **Unit Tests**: Test SaveCache() function
2. **Integration Tests**: Verify swap event parsing
3. **End-to-End Tests**: Full flow from swap → arbitrage
4. **Load Tests**: Handle 1000+ swaps/minute

---

## 🎯 Success Criteria

After fixes are applied, the bot should:

1. ✅ Discover 96 pools and save to disk
2. ✅ Detect 50+ swaps per minute
3. ✅ Update prices within 100ms of swap
4. ✅ Cache 20-30 active prices
5. ✅ Detect 5-10 arbitrage opportunities per hour
6. ✅ Restart in <5 seconds (load from cache)

---

## 📚 Code References

- **Pool Discovery**: `pkg/pools/discovery.go`
- **Price Engine**: `pkg/pricing/engine.go`
- **Market Updates**: `pkg/marketmanager/types.go:UpdatePriceData()`
- **Swap Processing**: `pkg/scanner/market/scanner.go`
- **Main Entry**: `cmd/mev-bot/main.go:256-323`

---

**Status**: ⚠️ **CRITICAL FIXES REQUIRED**
**Next Action**: Implement Fix #2 (Swap Detection) as highest priority
**Estimated Time**: 2-4 hours for all fixes
**Expected Value**: Enable arbitrage detection capability

---

*Document Version*: 1.0
*Last Updated*: October 30, 2025 18:15 UTC
*Analysis Duration*: 30 minutes
*Evidence Reviewed*: 10+ log files, 5 code modules, 3 cache files