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One of Proliferate’s most powerful features is the ability to see logs that led up to an error, giving you the complete picture of what happened.

​
How It Works

Every log entry and error event shares a trace ID, allowing you to see the exact sequence of events before an error occurred. 
┌─────────────────────────────────────────────────────────────────┐
│                      Page Load / Session                         │
│                                                                   │
│  ┌──────────┐  ┌──────────┐  ┌──────────┐  ┌──────────┐         │
│  │ Log      │──│ Log      │──│ Log      │──│ Error    │         │
│  │ trace_id │  │ trace_id │  │ trace_id │  │ trace_id │         │
│  │   abc    │  │   abc    │  │   abc    │  │   abc    │         │
│  └──────────┘  └──────────┘  └──────────┘  └──────────┘         │
│                                              ▲                    │
│                                              │                    │
│                          Error dashboard shows all these logs    │
└─────────────────────────────────────────────────────────────────┘

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Trace ID Generation

A trace ID is automatically generated:
  1. On page load: A new trace ID is created when the SDK initializes
  2. On SPA navigation: The trace ID is reset when the URL changes (via popstate)
// Access the current trace ID
const traceId = Proliferate.getTraceId();
console.log('Current trace:', traceId);
// Output: "a1b2c3d4e5f6g7h8i9j0k1l2m3n4o5p6"

​
Viewing Correlated Logs

In the error detail view:
1

Open Error Details

Click on an error to open details
2

Navigate to Logs Tab

Click the “Logs” tab
3

View Related Logs

See all logs with the same trace ID, ordered by time
Error: Cannot read property 'id' of undefined
────────────────────────────────────────────
trace_id: a1b2c3d4...

Related Logs (4):
────────────────────────────────────────────
14:23:45.123  info   User logged in                    user_id=123
14:23:46.456  info   Loading user profile              user_id=123
14:23:47.789  warn   Profile cache miss                user_id=123
14:23:48.012  error  Failed to fetch user data         status=500
14:23:48.015  [ERROR OCCURRED HERE]

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Automatic Correlation

When both logging and error tracking are enabled, correlation happens automatically: 
Proliferate.init({
  endpoint: 'https://api.proliferate.com/api/v1/errors',
  apiKey: 'pk_your_api_key',
  logs: {
    enabled: true,
  },
});

// These logs share a trace ID
Proliferate.logger.info('Starting checkout');
Proliferate.logger.info('Validating cart', { items: 3 });
Proliferate.logger.info('Processing payment');

// When this error is captured, all logs above are linked
try {
  await processPayment();
} catch (error) {
  Proliferate.captureException(error);
  // Error includes trace_id, linking it to the logs
}

​
Manual Trace ID Access

Use the trace ID for external correlation: 
const traceId = Proliferate.getTraceId();

// Include in API requests
fetch('/api/checkout', {
  headers: {
    'X-Trace-ID': traceId,
  },
});

// Include in your own logs
myLogger.info('Processing request', { trace_id: traceId });

// Include in support tickets
showError(`Something went wrong. Reference: ${traceId}`);

​
Server-Side Correlation (Python)

For full-stack correlation, pass the trace ID from frontend to backend: 
const traceId = Proliferate.getTraceId();

fetch('/api/process', {
  method: 'POST',
  headers: {
    'X-Trace-ID': traceId,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify(data),
});

​
SPA Navigation

In Single Page Applications, the trace ID resets on navigation: 
// Initial page load
// trace_id: aaa111...
Proliferate.logger.info('Home page loaded');

// User navigates to /dashboard (popstate event)
// trace_id: bbb222... (new trace)
Proliferate.logger.info('Dashboard loaded');

// User navigates to /profile
// trace_id: ccc333... (new trace)
Proliferate.logger.info('Profile loaded');
Each “page” in your SPA gets its own trace ID, keeping logs organized by user journey.

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Flush on Error

When an error is captured, logs are immediately flushed to ensure correlation: 
try {
  await riskyOperation();
} catch (error) {
  // These logs are guaranteed to be sent with the error
  Proliferate.logger.error('Operation failed', { details });
  Proliferate.captureException(error);
  // Logs are flushed immediately, not waiting for interval
}

​
Best Practices

async function checkout(cart) {
  Proliferate.logger.info('Checkout started', {
    items: cart.items.length,
    total: cart.total,
  });

  Proliferate.logger.info('Validating inventory');
  await validateInventory(cart);

  Proliferate.logger.info('Processing payment');
  await processPayment(cart);

  Proliferate.logger.info('Checkout completed', { orderId });
}

async function callExternalAPI(endpoint, data) {
  Proliferate.logger.info('Calling external API', {
    endpoint,
    payload_size: JSON.stringify(data).length,
  });

  try {
    const result = await fetch(endpoint, { body: JSON.stringify(data) });
    Proliferate.logger.info('API call succeeded', { status: result.status });
    return result;
  } catch (error) {
    Proliferate.logger.error('API call failed', { endpoint, error: error.message });
    throw error;
  }
}

Proliferate.logger.info('Processing order', {
  orderId: order.id,
  userId: user.id,
  amount: order.total,
});
// When viewing the error, you'll see exactly which order failed

​
Troubleshooting

  1. Check logging is enabled: 
    Proliferate.init({
  logs: { enabled: true },
});
  2. Check minLevel isn’t filtering out logs: 
    logs: { minLevel: 'debug' }
  3. Verify trace ID matches: 
    console.log('Trace:', Proliferate.getTraceId());
If you see logs from a different user action, the trace ID might not have reset on navigation. Check that your SPA router triggers popstate events.
Logs may be lost if:
  • Page closed before flush (use flushSync() in unload handlers)
  • Network errors prevented sending
  • Buffer was full and oldest logs were dropped