How does Vercel handle error handling and log management?

How does Vercel handle error handling and log management?

Vercel provides a comprehensive error handling and log management system that helps developers quickly identify, debug, and resolve issues. Understanding these features is crucial for maintaining production environment stability.

Log Management

1. Real-time Logs

Build Logs:

• Shows each step of the build process
• Includes dependency installation, build command execution, etc.
• Real-time build progress updates
• Displays build errors and warnings

Runtime Logs:

• Execution logs of Serverless Functions
• Request and response logs of API Routes
• Error stack traces
• Performance metrics

Access Logs:

• HTTP request logs
• Response times
• Status codes
• Request sources

2. Log Viewing Methods

Through Vercel Dashboard:

1. Go to project page
2. Select "Deployments" tab
3. Click on specific deployment
4. View "Build Logs" or "Function Logs"

Through Vercel CLI:

bash
# View logs for latest deployment
vercel logs

# View logs for specific deployment
vercel logs <deployment-url>

# Follow logs in real-time
vercel logs --follow

# View function logs
vercel logs --filter function

3. Log Filtering and Search

Filter Options:

• Filter by time range
• Filter by log level (Error, Warning, Info)
• Filter by function name
• Filter by request ID

Search Functionality:

• Keyword search
• Regular expression search
• Combined filter conditions

bash
# Search logs containing specific keywords
vercel logs --grep "error"

# Filter logs for specific function
vercel logs --filter "api/hello"

4. Log Export

Export Logs:

• Supports export in JSON format
• Can export logs for specific time ranges
• Used for offline analysis and archiving

bash
# Export logs to file
vercel logs --output logs.json

Error Handling

1. Build Errors

Common Build Errors:

Dependency Installation Failure:

shell
Error: Cannot find module 'react'

Solutions:

• Check dependencies in package.json
• Delete node_modules and package-lock.json
• Reinstall dependencies
• Check Node.js version compatibility

Build Command Failure:

shell
Error: Build failed with exit code 1

Solutions:

• Check if build command is correct
• View detailed error information
• Reproduce build process locally
• Check environment variable configuration

Type Errors:

shell
Error: Type 'string' is not assignable to type 'number'

Solutions:

• Fix TypeScript type errors
• Run local type checking
• Verify using --noEmit option

2. Runtime Errors

Serverless Functions Errors:

Timeout Error:

javascript
Error: Function execution timed out

Solutions:

• Optimize function execution time
• Increase function timeout limit
• Use async processing patterns
• Split long-running tasks

Out of Memory Error:

javascript
Error: JavaScript heap out of memory

Solutions:

• Increase function memory limit
• Optimize memory usage
• Use streaming processing
• Reduce data loading

Unhandled Exception:

javascript
Error: UnhandledPromiseRejectionWarning

Solutions:

• Add appropriate error handling
• Use try-catch blocks
• Implement global error handler
• Log all uncaught exceptions

3. Deployment Errors

Domain Configuration Error:

shell
Error: Domain verification failed

Solutions:

• Check DNS record configuration
• Wait for DNS propagation
• Verify domain ownership
• Check SSL certificate status

Environment Variable Error:

shell
Error: Missing required environment variable

Solutions:

• Check environment variable configuration
• Ensure all required variables are set
• Verify variable name spelling
• Redeploy project

Error Tracking Integration

1. Sentry Integration

Install Sentry:

bash
npm install @sentry/nextjs
npx @sentry/wizard -i nextjs

Configure Sentry:

javascript
// sentry.client.config.js
import * as Sentry from "@sentry/nextjs";

Sentry.init({
  dsn: process.env.NEXT_PUBLIC_SENTRY_DSN,
  tracesSampleRate: 1.0,
});

Capture Errors:

javascript
try {
  // Your code
} catch (error) {
  Sentry.captureException(error);
}

2. Other Error Tracking Services

LogRocket:

• Session replay
• Performance monitoring
• Error tracking

Rollbar:

• Real-time error reporting
• Error grouping
• Deployment tracking

Bugsnag:

• Automatic error reporting
• Error analysis
• User impact analysis

Performance Monitoring

1. Vercel Analytics

Integrate Analytics:

jsx
import { Analytics } from '@vercel/analytics/react';

export default function RootLayout({ children }) {
  return (
    <html>
      <body>
        {children}
        <Analytics />
      </body>
    </html>
  );
}

Monitoring Metrics:

• Web Vitals (LCP, FID, CLS)
• Page load times
• User behavior analytics
• Conversion rate tracking

2. Custom Performance Monitoring

Performance Tracking:

javascript
export async function getServerSideProps() {
  const start = Date.now();
  
  try {
    const data = await fetchData();
    const duration = Date.now() - start;
    
    // Log performance metrics
    console.log(`Data fetch duration: ${duration}ms`);
    
    return { props: { data } };
  } catch (error) {
    console.error('Error fetching data:', error);
    return { props: { error: true } };
  }
}

Debugging Tips

1. Local Debugging

Use Vercel CLI for Local Development:

bash
# Start local development server
vercel dev

# Simulate production environment
vercel dev --production

Local Environment Variables:

bash
# Pull environment variables
vercel env pull .env.local

# Push environment variables
vercel env push .env.local

2. Remote Debugging

Debug Using Logs:

javascript
export default async function handler(req, res) {
  console.log('Request received:', req.method, req.url);
  console.log('Request body:', req.body);
  
  try {
    const result = await processData(req.body);
    console.log('Processing result:', result);
    res.status(200).json(result);
  } catch (error) {
    console.error('Processing error:', error);
    res.status(500).json({ error: error.message });
  }
}

3. Performance Analysis

Use Chrome DevTools:

• Network panel for request analysis
• Performance panel for performance analysis
• Memory panel for memory usage analysis

Use Lighthouse:

• Run performance audits
• Identify performance bottlenecks
• Get optimization recommendations

Alerts and Notifications

1. Deployment Failure Alerts

Configure Alerts:

• Set up in Vercel Dashboard
• Email notifications
• Slack notifications
• Webhook notifications

Setup Steps:

1. Go to project settings
2. Select "Notifications"
3. Configure alert rules
4. Set notification channels

2. Error Rate Alerts

Monitor Error Rate:

• Set error rate thresholds
• Configure alert trigger conditions
• Define notification frequency

Integrate Third-Party Services:

• PagerDuty
• Opsgenie
• VictorOps

3. Performance Alerts

Web Vitals Alerts:

• LCP threshold alerts
• FID threshold alerts
• CLS threshold alerts

Custom Performance Metrics:

• API response times
• Database query times
• Function execution times

Best Practices

1. Logging

Structured Logging:

javascript
export default async function handler(req, res) {
  const logData = {
    timestamp: new Date().toISOString(),
    method: req.method,
    url: req.url,
    userId: req.headers['x-user-id'],
  };
  
  console.log(JSON.stringify(logData));
  
  try {
    const result = await processRequest(req);
    console.log(JSON.stringify({ ...logData, status: 'success' }));
    res.status(200).json(result);
  } catch (error) {
    console.error(JSON.stringify({ 
      ...logData, 
      status: 'error',
      error: error.message 
    }));
    res.status(500).json({ error: 'Internal Server Error' });
  }
}

Log Levels:

• Error: Serious errors
• Warning: Warning messages
• Info: General information
• Debug: Debug information

2. Error Handling

Global Error Handling:

javascript
// pages/_error.js
export default function Error({ statusCode }) {
  return (
    <div>
      <h1>Error: {statusCode}</h1>
      <p>Something went wrong</p>
    </div>
  );
}

Error.getInitialProps = ({ res, err }) => {
  const statusCode = res ? res.statusCode : err ? err.statusCode : 404;
  return { statusCode };
};

API Error Handling:

javascript
export default async function handler(req, res) {
  try {
    // Validate request
    if (!req.body) {
      return res.status(400).json({ error: 'Request body is required' });
    }
    
    // Process request
    const result = await processRequest(req.body);
    res.status(200).json(result);
  } catch (error) {
    // Log error
    console.error('API Error:', error);
    
    // Return appropriate error response
    if (error instanceof ValidationError) {
      return res.status(400).json({ error: error.message });
    }
    
    if (error instanceof AuthenticationError) {
      return res.status(401).json({ error: 'Unauthorized' });
    }
    
    // Default error response
    res.status(500).json({ error: 'Internal Server Error' });
  }
}

3. Monitoring and Analysis

Regular Log Review:

• Daily check of error logs
• Analyze error patterns
• Identify potential issues
• Develop improvement plans

Performance Monitoring:

• Monitor key metrics
• Set performance baselines
• Identify performance degradation
• Optimize slow endpoints

User Feedback:

• Collect user error reports
• Analyze user behavior
• Improve user experience
• Prioritize issues affecting users

Troubleshooting Process

1. Issue Identification

Symptom Identification:

• User reports issues
• Monitoring alerts triggered
• Logs show errors
• Performance metrics decline

2. Issue Diagnosis

Gather Information:

• View relevant logs
• Check error stacks
• Analyze performance data
• Reproduce issue

3. Issue Resolution

Implement Fix:

• Fix code
• Update configuration
• Optimize performance
• Test fix

4. Verification and Monitoring

Verify Fix:

• Deploy fix
• Test functionality
• Monitor logs
• Confirm issue resolved

Summary

Vercel's error handling and log management provides:

1. Comprehensive Logging: Build, runtime, and access logs
2. Powerful Error Tracking: Integration with third-party error tracking services
3. Real-time Monitoring: Performance metrics and error rate monitoring
4. Flexible Alerts: Multiple notification channels and alert rules
5. Convenient Debugging Tools: Local and remote debugging support

By effectively utilizing these features, developers can quickly identify and resolve issues, improving application stability and reliability.