Tracing Troubleshooting Guide

This guide covers common issues encountered when using EVM transaction tracing on Sei and provides practical solutions to resolve them.

Common Error Categories

1. Timeout Errors

Error: execution timeout

Cause: Tracer execution exceeded the configured timeout duration.

Solutions:


{
  "tracerConfig": {
    "timeout": "120s" // Increase timeout for complex traces
  }
}

Best Practices:

Start with shorter timeouts (30s) for testing
Increase gradually based on transaction complexity
Use built-in tracers when possible (they’re faster)
Optimize JavaScript tracer code for performance

2. Memory Limit Errors

Error: out of memory or memory limit exceeded

Cause: Tracer collected too much data or inefficient memory usage.

Solutions:


{
  "tracerConfig": {
    "enableMemory": false, // Disable memory tracing
    "enableStack": false, // Disable stack tracing
    "enableStorage": false // Disable storage tracing
  }
}

Memory-Efficient Tracer Pattern:


{
  "tracer": `{
    // Use counters instead of arrays
    summary: {
      totalGas: 0,
      operationCount: 0,
      expensiveOps: 0
    },
 
    step: function(log, db) {
      this.summary.totalGas += log.getCost();
      this.summary.operationCount++;
 
      // Only track expensive operations
      if (log.getCost() > 1000) {
        this.summary.expensiveOps++;
      }
    },
 
    result: function(ctx, db) {
      return this.summary; // Return summary, not raw data
    }
  }`
}

3. JavaScript Tracer Errors

Error: SyntaxError or ReferenceError in JavaScript tracer

Common Issues:


// ❌ Incorrect - Missing quotes
{
  "tracer": `{
    step: function(log, db) {
      var op = log.op.toString();
      if (op == SSTORE) { // Missing quotes around SSTORE
        // ...
      }
    }
  }`
}
 
// ✅ Correct - Proper quotes
{
  "tracer": `{
    step: function(log, db) {
      var op = log.op.toString();
      if (op == "SSTORE") { // Quoted properly
        // ...
      }
    }
  }`
}

Debugging JavaScript Tracers:


{
  "tracer": `{
    errors: [],
 
    step: function(log, db) {
      try {
        // Your tracer logic here
        var op = log.op.toString();
        // ...
      } catch (e) {
        this.errors.push({
          error: e.toString(),
          pc: log.getPC(),
          op: log.op.toString()
        });
      }
    },
 
    result: function(ctx, db) {
      return {
        data: this.data,
        errors: this.errors // Check for errors
      };
    }
  }`
}

4. Network and Connection Issues

Error: connection refused or network timeout

Solutions:


# Check if node is running
curl -X POST -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}' \
  http://localhost:8545
 
# Test with different timeout
curl --connect-timeout 30 --max-time 120 \
  -X POST -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","method":"debug_traceTransaction","params":["0x..."],"id":1}' \
  http://localhost:8545

5. Transaction Not Found

Error: transaction not found

Debugging Steps:


# 1. Verify transaction exists
curl -X POST -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","method":"eth_getTransactionByHash","params":["0x..."],"id":1}' \
  http://localhost:8545
 
# 2. Check if transaction is in a finalized block
curl -X POST -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","method":"eth_getTransactionReceipt","params":["0x..."],"id":1}' \
  http://localhost:8545
 
# 3. Ensure node is fully synced
curl -X POST -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","method":"eth_syncing","params":[],"id":1}' \
  http://localhost:8545

Performance Optimization

Tracer Performance Tips

Limit Data Collection:


{
  "tracer": `{
    data: [],
    maxEntries: 1000, // Limit data collection
 
    step: function(log, db) {
      if (this.data.length < this.maxEntries) {
        // Only collect limited data
        this.data.push({
          pc: log.getPC(),
          op: log.op.toString(),
          gas: log.getGas()
        });
      }
    }
  }`
}

Use Efficient Data Structures:


// ❌ Inefficient - Object lookups
{
  "tracer": `{
    operations: {},
 
    step: function(log, db) {
      var op = log.op.toString();
      if (!this.operations[op]) {
        this.operations[op] = 0;
      }
      this.operations[op]++;
    }
  }`
}
 
// ✅ Efficient - Direct assignment
{
  "tracer": `{
    operations: {},
 
    step: function(log, db) {
      var op = log.op.toString();
      this.operations[op] = (this.operations[op] || 0) + 1;
    }
  }`
}

Selective Tracing:


{
  "tracer": `{
    step: function(log, db) {
      var op = log.op.toString();
 
      // Only trace specific operations
      if (op == "SSTORE" || op == "SLOAD" || op == "CALL") {
        // Process only important operations
        this.processOperation(log, db);
      }
    }
  }`
}

Node Configuration for Better Performance


# In your node configuration
[evm]
# Increase trace timeout
trace-timeout = "300s"
 
# Increase memory limits
trace-memory-limit = "1GB"
 
# Enable trace caching
trace-cache-size = 1000

Debugging Workflows

1. Failed Transaction Analysis


#!/bin/bash
 
TX_HASH="0x..."
 
echo "1. Checking if transaction exists..."
curl -s -X POST -H "Content-Type: application/json" \
  --data "{\"jsonrpc\":\"2.0\",\"method\":\"eth_getTransactionByHash\",\"params\":[\"$TX_HASH\"],\"id\":1}" \
  http://localhost:8545 | jq '.result'
 
echo "2. Getting transaction receipt..."
curl -s -X POST -H "Content-Type: application/json" \
  --data "{\"jsonrpc\":\"2.0\",\"method\":\"eth_getTransactionReceipt\",\"params\":[\"$TX_HASH\"],\"id\":1}" \
  http://localhost:8545 | jq '.result.status'
 
echo "3. Tracing transaction..."
curl -s -X POST -H "Content-Type: application/json" \
  --data "{\"jsonrpc\":\"2.0\",\"method\":\"debug_traceTransaction\",\"params\":[\"$TX_HASH\",{\"tracer\":\"callTracer\"}],\"id\":1}" \
  http://localhost:8545 | jq '.result'

2. Gas Optimization Workflow


// Step 1: Identify expensive operations
const expensiveOpsTracer = `{
  expensive: [],
  threshold: 1000,
  
  step: function(log, db) {
    var cost = log.getCost();
    if (cost > this.threshold) {
      this.expensive.push({
        pc: log.getPC(),
        op: log.op.toString(),
        cost: cost
      });
    }
  },
  
  result: function(ctx, db) {
    this.expensive.sort((a, b) => b.cost - a.cost);
    return {
      totalExpensive: this.expensive.length,
      topExpensive: this.expensive.slice(0, 10)
    };
  }
}`;
 
// Step 2: Analyze storage operations
const storageTracer = `{
  storageOps: 0,
  storageGas: 0,
  
  step: function(log, db) {
    var op = log.op.toString();
    if (op == "SSTORE" || op == "SLOAD") {
      this.storageOps++;
      this.storageGas += log.getCost();
    }
  },
  
  result: function(ctx, db) {
    return {
      storageOperations: this.storageOps,
      storageGasCost: this.storageGas,
      averageCost: this.storageOps > 0 ? this.storageGas / this.storageOps : 0
    };
  }
}`;

Error Code Reference

Common HTTP Error Codes

Code	Error	Solution
400	Bad Request	Check JSON-RPC format and parameters
404	Not Found	Verify transaction hash and node sync status
500	Internal Server Error	Check node logs and resource limits
503	Service Unavailable	Node may be syncing or overloaded

Tracer-Specific Errors

Error	Cause	Solution
`execution timeout`	Tracer took too long	Increase timeout or optimize tracer
`out of memory`	Too much data collected	Reduce data collection or disable memory tracing
`invalid tracer`	JavaScript syntax error	Validate tracer syntax
`tracer not found`	Built-in tracer doesn’t exist	Check available tracers

Best Practices Summary

✅ Do’s

Start Simple: Begin with built-in tracers before custom JavaScript
Set Timeouts: Always configure appropriate timeouts
Limit Data: Collect only necessary information
Test Incrementally: Test tracers on simple transactions first
Monitor Resources: Watch memory and CPU usage
Cache Results: Store expensive trace results when possible

❌ Don’ts

Don’t Collect Everything: Avoid tracing all operations unnecessarily
Don’t Ignore Errors: Always handle tracer errors gracefully
Don’t Use Complex Logic: Keep tracer step functions simple
Don’t Forget Timeouts: Never run tracers without timeout limits
Don’t Trace in Production: Avoid heavy tracing on production nodes

Getting Help

If you encounter issues not covered in this guide:

Check Node Logs: Look for error messages in your Sei node logs
Verify Configuration: Ensure your node has tracing enabled
Test Connectivity: Confirm RPC endpoints are accessible
Simplify Tracers: Try built-in tracers first
Community Support: Ask in the Sei Discord #dev-support channel

When reporting issues, include your tracer code, the transaction hash, and any error messages you receive. This helps the community provide better assistance.