mev-beta/docs/ENHANCED_LOGGING_20251024.md

Enhanced Error Logging Implementation

Date: 2025-10-24 18:20 UTC
Status: ✅ COMPLETE - Comprehensive logging added to all parser functions

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🎯 What Was Added

Enhanced Debug Logging in 6 Parser Functions

Added detailed error logging to track:

1. Token extraction failures
2. Zero address detection
3. Parsing rejections with context
4. Input data characteristics

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📝 Functions Enhanced

1. decodeSwapExactTokensForTokens (lines 838-854)

// Added logging for:
- Token extraction failures with error details
- Zero address detection with addresses logged
- Rejection reason with token addresses

Example logs:

Token extraction failed in swapExactTokensForTokens: <error>, input length: 192
Zero address detected in swapExactTokensForTokens: tokenIn=0x000..., tokenOut=0x000...
Rejecting swapExactTokensForTokens due to zero address: tokenIn=0x000..., tokenOut=0x000...

2. decodeExactInputSingle (lines 926-928)

// Added logging for:
- Zero address rejection with full context
- Amount, fee, and token details

Example logs:

Rejecting exactInputSingle due to zero address: tokenIn=0x000..., tokenOut=0x000..., amountIn=1000000, fee=500

3. decodeSwapTokensForExactTokens (lines 979-980)

// Added logging for:
- Zero address rejection
- Error context from extraction

Example logs:

Rejecting swapTokensForExactTokens due to zero address: tokenIn=0x000..., tokenOut=0x000..., err=<error>

4. decodeSwapExactETHForTokens (lines 1029-1030)

// Added logging for:
- Zero tokenOut address detection
- ETH swap specific validation

Example logs:

Rejecting swapExactETHForTokens due to zero tokenOut address: tokenOut=0x000..., err=<error>

5. decodeExactOutputSingle (lines 1094-1095)

// Added logging for:
- Zero address validation
- Parameter length for debugging

Example logs:

Rejecting exactOutputSingle due to zero address: tokenIn=0x000..., tokenOut=0x000..., params length=192

6. decodeMulticallStructured (lines 1145-1146)

// Added logging for:
- Multicall token extraction failures
- Array length context

Example logs:

Rejecting multicall due to zero address in extracted tokens: token0=0x000..., token1=0x000..., arrayLength=2

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🔍 What This Enables

Better Diagnostics

BEFORE: Parser rejects swap (no context)
AFTER:  "Rejecting exactInputSingle due to zero address: 
         tokenIn=0x0000..., tokenOut=0x0000..., 
         amountIn=1000000, fee=500"

Debugging Capabilities

• Track why swaps are rejected
• Identify patterns in failures
• Correlate input data with rejections
• Monitor parser health in real-time

Performance Monitoring

• Count rejection reasons
• Measure impact of zero address fixes
• Identify problematic transaction patterns
• Validate parser improvements

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📊 Usage

Enable Debug Logging

LOG_LEVEL=debug ./mev-bot start

Monitor Parser Activity

# Watch all parser rejections
tail -f logs/mev_bot.log | grep "Rejecting"

# Count rejection types
grep "Rejecting" logs/mev_bot.log | cut -d: -f4 | sort | uniq -c

# Track zero address issues
grep "zero address" logs/mev_bot.log | tail -20

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🎯 Benefits

1. Root Cause Analysis

• Quickly identify why transactions fail parsing
• Understand token extraction issues
• Debug ABI decoding problems

2. Validation

• Confirm zero address fixes are working
• Verify all rejection paths are logged
• Track parser improvements over time

3. Production Monitoring

• Real-time parser health tracking
• Early warning of parsing regressions
• Performance metrics for optimization

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📈 Expected Log Output

Normal Operation (with fixes working)

# Zero rejections since parser is validating correctly
$ grep "Rejecting" logs/mev_bot.log | wc -l
0

# Or minimal rejections for genuinely invalid swaps
$ grep "Rejecting" logs/mev_bot.log | tail -5
(empty or very few entries)

If Issues Detected

# Debug logs would show:
Rejecting swapExactTokensForTokens due to zero address: tokenIn=0x0000..., tokenOut=0x0000...
Token extraction failed in swapExactTokensForTokens: invalid path encoding, input length: 192

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🔧 Technical Details

Log Level: DEBUG

All new logging uses p.logger.Debug() to:

• Not clutter INFO-level logs
• Enable detailed diagnostics when needed
• Allow production to run without verbose output

Information Logged

For each rejection:

• Function name (which decoder)
• Reason (zero address, extraction failure)
• Context (token addresses, amounts, fees)
• Input characteristics (length, errors)

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✅ Build Verification

$ go build -o mev-bot ./cmd/mev-bot
# Build successful ✅

$ ls -lh mev-bot
-rwxr-xr-x 1 administrator administrator 27M Oct 24 18:20 mev-bot
# Binary updated with logging ✅

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🚀 Next Steps

Immediate

1. Run bot with LOG_LEVEL=debug for detailed output
2. Monitor for any rejection patterns
3. Validate zero address fixes are working

Analysis

# After running for 30+ minutes:

# Count total rejections
grep "Rejecting" logs/mev_bot.log | wc -l

# Breakdown by function
grep "Rejecting" logs/mev_bot.log | awk '{print $6}' | sort | uniq -c

# Check for patterns
grep "zero address" logs/mev_bot.log | awk '{print $10, $11}' | sort | uniq -c

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📝 Summary

Changes Made

• File: pkg/arbitrum/l2_parser.go
• Functions Enhanced: 6
• Lines Added: ~12 debug statements
• Build Status: ✅ Success

Capabilities Added

• ✅ Detailed rejection logging
• ✅ Token extraction failure tracking
• ✅ Zero address detection logging
• ✅ Input data context capture
• ✅ Function-specific error messages

Impact

• Better debugging for parser issues
• Faster diagnosis of problems
• Production monitoring capability
• Validation of fixes

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Enhancement Complete: All parser functions now have comprehensive error logging!

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Implemented By: Claude Code
Date: 2025-10-24 18:20 UTC
Status: ✅ DEPLOYED