Error Handling

Handle errors gracefully and provide clear feedback to users.

Error Response Format

All WalletGate API errors follow this consistent structure:

{
  "success": false,
  "error": {
    "code": "ERROR_CODE",
    "message": "Human-readable error message",
    "field": "fieldName",  // Optional: which field caused the error
    "details": {           // Optional: additional context
      "key": "value"
    }
  }
}

HTTP Status Codes

Code	Meaning	When It Happens
200	Success	Request completed successfully
201	Created	Resource created (e.g., new session)
400	Bad Request	Invalid input or validation error
401	Unauthorized	Missing or invalid API key
403	Forbidden	Quota exceeded or insufficient permissions
404	Not Found	Resource doesn't exist
429	Too Many Requests	Rate limit exceeded
500	Internal Server Error	Something went wrong on our end

Common Errors

Authentication Errors

Missing API Key

{
  "success": false,
  "error": {
    "code": "MISSING_API_KEY",
    "message": "No API key provided. Include Authorization header with Bearer token."
  }
}

Fix:

// ✅ Correct
headers: {
  'Authorization': `Bearer ${apiKey}`,
}

// ❌ Wrong - missing header
headers: {}

Invalid API Key

{
  "success": false,
  "error": {
    "code": "INVALID_API_KEY",
    "message": "API key is invalid or has been revoked."
  }
}

Causes:

• Key was deleted
• Typo in key
• Key format incorrect

Fix: Verify key in dashboard

Validation Errors

Invalid Check Type

{
  "success": false,
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Invalid check type",
    "field": "checks[0].type",
    "details": {
      "allowed": ["age_over", "residency_eu", "identity_verified"]
    }
  }
}

Fix:

// ✅ Correct
checks: [{ type: 'age_over', value: 18 }]

// ❌ Wrong
checks: [{ type: 'age_check', value: 18 }]

Missing Required Field

{
  "success": false,
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "checks is required",
    "field": "checks"
  }
}

Invalid URL Format

{
  "success": false,
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Invalid redirect URL",
    "field": "redirectUrl",
    "details": {
      "value": "not-a-url",
      "expected": "Valid HTTPS URL"
    }
  }
}

Quota Errors

Monthly Limit Exceeded

{
  "success": false,
  "error": {
    "code": "QUOTA_EXCEEDED",
    "message": "Monthly verification quota exceeded. Upgrade your plan or wait for reset.",
    "details": {
      "used": 1000,
      "limit": 1000,
      "resetAt": "2024-02-01T00:00:00Z",
      "upgradeUrl": "https://console.walletgate.app/admin"
    }
  }
}

Fix: Upgrade plan or wait for monthly reset

Rate Limit Errors

Too Many Requests

{
  "success": false,
  "error": {
    "code": "RATE_LIMIT_EXCEEDED",
    "message": "Too many requests. Please slow down.",
    "details": {
      "limit": 10,
      "remaining": 0,
      "resetAt": 1704067260000
    }
  }
}

Headers included:

X-RateLimit-Limit: 10
X-RateLimit-Remaining: 0
X-RateLimit-Reset: 1704067260

Fix: Implement exponential backoff

Resource Errors

Session Not Found

{
  "success": false,
  "error": {
    "code": "SESSION_NOT_FOUND",
    "message": "Verification session not found or expired."
  }
}

Causes:

• Session ID doesn't exist
• Session expired (15 min timeout)
• Typo in session ID

Verification Errors

User Declined

{
  "success": false,
  "error": {
    "code": "USER_DECLINED",
    "message": "User cancelled verification in wallet."
  }
}

Session Expired

{
  "success": false,
  "error": {
    "code": "SESSION_EXPIRED",
    "message": "Verification session expired after 15 minutes."
  }
}

Invalid Credentials

{
  "success": false,
  "error": {
    "code": "INVALID_CREDENTIALS",
    "message": "Certificate validation failed",
    "details": {
      "reason": "Certificate revoked by issuer",
      "issuer": "DE Trust Service Provider"
    }
  }
}

Error Handling Patterns

Basic Try-Catch

import { WalletGate, WalletGateApiError } from '@walletgate/eudi';

const client = new WalletGate({
  apiKey: process.env.WALLETGATE_API_KEY,
});

try {
  const session = await client.startVerification({
    checks: [{ type: 'age_over', value: 18 }],
  });

  console.log('Session created:', session.id);
} catch (error) {
  if (error instanceof WalletGateApiError) {
    switch (error.code) {
      case 'RATE_LIMIT_EXCEEDED':
        console.error('Rate limit exceeded. Please wait or upgrade.');
        break;
      case 'UNAUTHORIZED':
        console.error('Invalid API key. Check configuration.');
        break;
      case 'VALIDATION_ERROR':
        console.error('Invalid request. Check your payload.');
        break;
      default:
        console.error(`API error: ${error.message} (${error.code || 'UNKNOWN'})`);
    }
    console.error('Details:', error.details);
  } else {
    console.error('Network error:', (error as any)?.message || String(error));
  }
}

Retry with Exponential Backoff

async function createSessionWithRetry(
  checks: any[],
  maxRetries: number = 3
): Promise<VerificationSession> {
  let lastError: Error;

  for (let attempt = 0; attempt < maxRetries; attempt++) {
    try {
      return await client.startVerification({ checks });
    } catch (error) {
      lastError = error;

      // Don't retry on validation errors or quota errors
      if (error instanceof WalletGateApiError && (error.code === 'VALIDATION_ERROR' || error.code === 'RATE_LIMIT_EXCEEDED')) {
        throw error;
      }

      // Exponential backoff
      const delay = Math.pow(2, attempt) * 1000; // 1s, 2s, 4s
      console.log(`Retry attempt ${attempt + 1} after ${delay}ms`);
      await new Promise(resolve => setTimeout(resolve, delay));
    }
  }

  throw lastError;
}

User-Friendly Error Messages

function getUserFriendlyErrorMessage(error: unknown): string {
  const errorCode = error instanceof WalletGateApiError ? error.code : undefined;

  const messages: Record<string, string> = {
    RATE_LIMIT_EXCEEDED: 'We\'ve reached our verification limit. Please try again later or upgrade.',
    USER_DECLINED: 'Verification was cancelled. Please try again when you\'re ready.',
    SESSION_EXPIRED: 'Verification link expired. Click below to generate a new one.',
    INVALID_CREDENTIALS: 'We couldn\'t verify your credentials. Please ensure your wallet is up to date.',
    UNAUTHORIZED: 'Authentication failed. Check your API key.',
  };

  return messages[errorCode] || 'Something went wrong. Please try again or contact support.';
}

// Usage in UI
try {
  await createSession();
} catch (error) {
  showErrorToast(getUserFriendlyErrorMessage(error));
}

Frontend Error Handling

React Example

import { useState } from 'react';

function VerificationButton() {
  const [error, setError] = useState<string | null>(null);
  const [loading, setLoading] = useState(false);

  const handleVerify = async () => {
    setError(null);
    setLoading(true);

    try {
      const response = await fetch('/api/verify/create', {
        method: 'POST',
      });

      if (!response.ok) {
        const data = await response.json();
        throw new Error(data.error || data.message || 'Request failed');
      }

      const { sessionId } = await response.json();
      // Show QR code...
    } catch (err) {
      setError(err.message);
    } finally {
      setLoading(false);
    }
  };

  return (
    <div>
      <button onClick={handleVerify} disabled={loading}>
        {loading ? 'Creating session...' : 'Verify Age'}
      </button>

      {error && (
        <div className="error-message">
          ⚠️ {error}
        </div>
      )}
    </div>
  );
}

Logging Best Practices

What to Log

// ✅ Log these
console.error('Verification failed:', {
  sessionId: session.id,
  errorCode: error.code,
  timestamp: new Date().toISOString(),
  userId: metadata.userId, // If applicable
});

// ❌ Don't log these
console.error('Error:', {
  apiKey: process.env.WALLETGATE_API_KEY, // NEVER log API keys!
  rawCredentials: credentials, // NEVER log PII!
});

Structured Logging

import { WalletGateApiError } from '@walletgate/eudi';
import pino from 'pino';

const logger = pino();

try {
  await client.startVerification({ checks });
} catch (error) {
  if (!(error instanceof WalletGateApiError)) throw error;
  logger.error({
    msg: 'Session creation failed',
    errorCode: error.code,
    errorMessage: error.message,
    endpoint: '/v1/verify/sessions',
    method: 'POST',
    timestamp: Date.now(),
  });
}

Monitoring & Alerts

Set Up Alerts

Monitor these error rates:

• High priority:

  • Authentication errors > 5%
  • Internal server errors > 0.1%
  • Quota exceeded (upgrade needed)

• Medium priority:

  • Validation errors > 10%
  • Rate limit errors > 1%

• Low priority:

  • User declined > 20%
  • Session expired > 10%

Error Rate Calculation

const errorRate = (failedRequests / totalRequests) * 100;

if (errorRate > 5) {
  alertTeam({
    message: `High error rate: ${errorRate}%`,
    severity: 'high',
    details: {
      totalRequests,
      failedRequests,
      timeWindow: '5 minutes',
    },
  });
}

Complete Error Code Reference

Code	HTTP	Description	Action
UNAUTHORIZED	401	Missing/invalid API key	Check dashboard / config
RATE_LIMIT_EXCEEDED	429	Too many requests	Implement backoff
VALIDATION_ERROR	400	Invalid input	Fix request body
NOT_FOUND	404	Session doesn't exist	Check session ID
REDIRECT_ALLOWLIST_REQUIRED	400	Redirect allowlist not configured	Configure allowlist in dashboard
REDIRECT_ORIGIN_NOT_ALLOWED	400	Redirect origin not allowlisted	Add origin to allowlist
IDEMPOTENCY_KEY_INVALID	400	Invalid Idempotency-Key header	Fix key (1-256 printable ASCII)
IDEMPOTENCY_CONFLICT	409	Same key is still processing	Retry after 1s
IDEMPOTENCY_PAYLOAD_MISMATCH	422	Same key used with different body	Use a new key
INTERNAL_ERROR	500	Server error	Retry, contact support

View error code reference →

Testing Error Scenarios

Force Errors in Test Mode

// Force validation error
await client.startVerification({
  checks: [{ type: 'invalid_type', value: 18 }], // Wrong type
});

// Force session not found
await client.getResult('00000000-0000-0000-0000-000000000000');

Simulate Network Errors

// Simulate timeout
const client = new WalletGate({
  apiKey: process.env.WALLETGATE_API_KEY,
  timeout: 1, // 1ms timeout - will always fail
});

// Simulate network error
// (disconnect internet, use invalid base URL, etc.)

Next Steps

• 🔄 Verification Flow
• 🔐 Authentication
• 🔔 Webhooks
• 📚 API Reference

Need Help?

• 📧 Email: [email protected]
• 📖 FAQ
• 💬 Book a demo