Error Grouping

Understand how VIJ groups similar errors and implements fingerprinting

VIJ automatically groups similar errors to help you identify patterns, reduce noise, and focus on unique issues rather than thousands of duplicate errors.

Why Error Grouping Matters

Without error grouping, a single bug could generate thousands of individual error logs, making it impossible to:

• Identify unique issues
• Prioritize critical bugs
• Understand error frequency
• Track resolution progress

Example Problem:

// This bug generates 10,000 errors in production
users.forEach(user => {
  console.log(user.name.toUpperCase()); // TypeError if name is undefined
});

Without grouping: 10,000 separate error entries With grouping: 1 error group with count of 10,000 occurrences

How Error Grouping Works

VIJ uses fingerprinting to identify similar errors and group them together.

Fingerprint Generation

A fingerprint is a unique hash generated from:

1. Error name - The error type (TypeError, ReferenceError, etc.)
2. Normalized message - Error message with dynamic values removed
3. Stack trace signature - Top 3-5 stack frames

// Example errors that get grouped together
Error: User 123 not found       → fingerprint: "Error:User_not_found:fetchUser:api.js:45"
Error: User 456 not found       → fingerprint: "Error:User_not_found:fetchUser:api.js:45"
Error: User 789 not found       → fingerprint: "Error:User_not_found:fetchUser:api.js:45"

Normalization Process

Dynamic values are normalized to create consistent fingerprints:

Numbers

// Original messages
"Order 12345 failed"
"Order 67890 failed"
"Order 11111 failed"

// Normalized
"Order <number> failed"

// Fingerprint includes
"Order_failed"

Stack Trace Fingerprinting

VIJ analyzes stack traces to identify the error’s origin:

// Stack trace
Error: Payment failed
    at processPayment (payment.js:45:12)      ← Frame 1 (most important)
    at handleCheckout (checkout.js:123:5)     ← Frame 2
    at onClick (Button.tsx:67:20)             ← Frame 3
    at handleClick (react-dom.js:2345:10)     ← Frame 4 (library code)
    at ... (more frames)

// Fingerprint uses top 3 application frames
"processPayment:payment.js:45"
"handleCheckout:checkout.js:123"
"onClick:Button.tsx:67"

// Library code frames are excluded

Why top frames matter most:

• Top frames show where the error originated
• Middle frames show the call path
• Bottom frames are usually library/framework code (less useful for grouping)

Grouping Algorithm

The complete fingerprinting algorithm:

function generateFingerprint(error: ErrorLog): string {
  // 1. Extract error name
  const errorName = error.name || 'Error';

  // 2. Normalize message
  const normalizedMessage = normalizeMessage(error.message);

  // 3. Extract stack frames
  const frames = parseStackTrace(error.stack);

  // 4. Get top application frames (skip library code)
  const appFrames = frames
    .filter(frame => !isLibraryCode(frame))
    .slice(0, 3);

  // 5. Create stack signature
  const stackSignature = appFrames
    .map(frame => `${frame.function}:${frame.file}:${frame.line}`)
    .join('|');

  // 6. Combine into fingerprint
  const fingerprint = `${errorName}:${normalizedMessage}:${stackSignature}`;

  // 7. Hash for consistency
  return hash(fingerprint);
}

function normalizeMessage(message: string): string {
  return message
    .replace(/\d+/g, '<number>')                    // Numbers
    .replace(/[0-9a-f-]{36}/g, '<uuid>')           // UUIDs
    .replace(/\/[\w\/.-]+/g, '<path>')             // File paths
    .replace(/\d{4}-\d{2}-\d{2}/g, '<date>')       // Dates
    .replace(/user_\w+|id_\w+/g, '<id>')           // IDs
    .replace(/\s+/g, '_')                           // Normalize whitespace
    .toLowerCase();
}

Viewing Error Groups

Groups Dashboard

Navigate to /groups to view all error groups:

Information Displayed:

• Error Message - Representative message from the group
• Count - Total occurrences
• First Seen - When this error first appeared
• Last Seen - Most recent occurrence
• Severity - Highest severity in the group
• Affected Apps - Which applications are impacted

Sorting Options:

• By count (most frequent first)
• By recency (most recent first)
• By first occurrence (oldest first)
• By severity (critical first)

Group Details

Click any group to see:

1. All occurrences - Every instance of this error
2. Frequency chart - Error rate over time
3. Affected users - If user metadata is attached
4. Common metadata - Shared context across occurrences

Example Use Case:

Group: TypeError: Cannot read property 'name' of undefined
Count: 2,547 occurrences
First Seen: 3 days ago
Last Seen: 2 minutes ago

Common metadata:
- Feature: checkout (95% of occurrences)
- Browser: Chrome (78%), Safari (22%)
- Environment: production (100%)

Custom Grouping Strategies

VIJ supports custom grouping for specific use cases.

Group by Metadata

Group errors by custom metadata fields:

// Capture errors with custom grouping key
captureException(error, {
  groupKey: "checkout-payment-error", // Custom group identifier
  feature: "checkout",
  step: "payment"
});

Manual Grouping

Override automatic grouping:

// Force errors into same group
captureException(error1, {
  fingerprint: "payment-processing-error"
});

captureException(error2, {
  fingerprint: "payment-processing-error"
});

// These will be grouped together regardless of stack trace

Use manual grouping when automatic grouping is too granular or when you want to track a specific error pattern.

Group by Environment

Separate errors by environment even if they’re the same:

// Production errors grouped separately from staging
init({
  appId: "my-app",
  environment: "production" // Groups are environment-specific
});

Grouping Configuration

Configure grouping behavior in VIJ Admin.

Group Merge Rules

Define rules to merge groups:

lib/grouping.ts

export const groupingRules = [
  {
    name: "Network Errors",
    pattern: /fetch failed|network error|connection refused/i,
    mergeInto: "network-errors"
  },
  {
    name: "Auth Errors",
    pattern: /unauthorized|forbidden|authentication failed/i,
    mergeInto: "auth-errors"
  }
];

Stack Frame Filtering

Exclude certain files from fingerprinting:

const excludeFromFingerprint = [
  'node_modules/',
  'webpack/',
  'react-dom',
  'next/dist/'
];

Why exclude library code:

• Library code is the same across errors
• Focus on application-specific code
• More meaningful grouping

Group Size Limits

Configure maximum group sizes:

const groupingConfig = {
  maxGroupSize: 10000,        // Split large groups
  mergeThreshold: 0.85,       // Similarity threshold (0-1)
  stackFrameDepth: 3,         // Number of frames to use
  normalizeUrls: true,        // Normalize URLs in messages
  normalizeNumbers: true      // Replace numbers with placeholders
};

Advanced Grouping Patterns

Similarity-Based Grouping

Group errors by similarity score:

function calculateSimilarity(error1: Error, error2: Error): number {
  const messageSimilarity = levenshteinDistance(
    error1.message,
    error2.message
  );

  const stackSimilarity = compareStackTraces(
    error1.stack,
    error2.stack
  );

  return (messageSimilarity + stackSimilarity) / 2;
}

// Merge if similarity > 85%
if (calculateSimilarity(error1, error2) > 0.85) {
  mergeIntoSameGroup(error1, error2);
}

Machine Learning Grouping

Use ML to identify error patterns:

# Example: Use embeddings for error clustering
from sentence_transformers import SentenceTransformer

model = SentenceTransformer('all-MiniLM-L6-v2')

# Generate embeddings for error messages
embeddings = model.encode([
  "Payment failed for user 123",
  "Payment failed for user 456",
  "Database connection timeout"
])

# Cluster similar errors
from sklearn.cluster import DBSCAN
clusters = DBSCAN(eps=0.3, min_samples=2).fit(embeddings)

ML-based grouping is an advanced feature not included in the default VIJ installation but can be implemented as a custom extension.

Grouping Best Practices

Use meaningful error messages

Good:

throw new Error("Payment processing failed: invalid card");
throw new Error("User authentication failed: invalid token");

Bad:

throw new Error("Error");
throw new Error("Something went wrong");

Specific messages create better groups.

Include context in metadata, not messages

Good:

captureException(
  new Error("Payment failed"),
  { userId: 123, orderId: 456 }
);

Bad:

captureException(
  new Error(`Payment failed for user ${userId} order ${orderId}`)
);

Dynamic values in messages prevent proper grouping.

Use custom error classes

class PaymentError extends Error {
  constructor(message, code) {
    super(message);
    this.name = "PaymentError";
    this.code = code;
  }
}

throw new PaymentError("Card declined", "CARD_DECLINED");

Custom error classes create distinct groups.

Review groups regularly

• Check for over-grouping (unrelated errors grouped together)
• Check for under-grouping (same error split into multiple groups)
• Adjust normalization rules as needed
• Archive resolved groups

Use environment-specific grouping

// Different environments, different groups
init({
  appId: "my-app",
  environment: process.env.NODE_ENV,
  metadata: {
    groupEnvironment: process.env.NODE_ENV
  }
});

Prevents production errors from mixing with development/staging.

Troubleshooting Grouping Issues

Errors not grouping as expected

Symptom: Similar errors appearing as separate groups

Causes:

• Dynamic values in error messages
• Different stack traces
• Different error names

Solutions:

1. Use consistent error messages
2. Check stack trace consistency
3. Use custom fingerprinting
4. Review normalization rules

Debug:

// Log fingerprints to see why errors aren't grouping
console.log(generateFingerprint(error1));
console.log(generateFingerprint(error2));

Too many groups

Symptom: Hundreds of small groups instead of a few large ones

Causes:

• Unique error messages
• Different stack traces
• Over-specific fingerprinting

Solutions:

• Increase normalization (more aggressive pattern matching)
• Use custom grouping keys
• Merge related groups manually
• Reduce stack frame depth

Groups too large

Symptom: Single group with thousands of unrelated errors

Causes:

• Generic error messages (“Error”, “Something went wrong”)
• Over-aggressive normalization
• Missing stack traces

Solutions:

• Use specific error messages
• Include stack traces
• Add more context to fingerprints
• Split large groups manually

Groups merging incorrectly

Symptom: Unrelated errors in the same group

Causes:

• Overly aggressive normalization
• Similar but different errors
• Missing stack frame information

Solutions:

• Reduce normalization
• Use custom fingerprinting
• Include more stack frames
• Use metadata for additional grouping

Group Management

Archive Resolved Groups

Mark groups as resolved:

// In VIJ Admin
POST /api/groups/:groupId/resolve
{
  "resolved": true,
  "resolvedBy": "[e-mail]",
  "resolvedAt": "2024-01-01T12:00:00Z",
  "resolution": "Fixed in commit abc123"
}

Split Groups

Split a group into multiple groups:

// Split by specific criteria
POST /api/groups/:groupId/split
{
  "splitBy": "metadata.feature",
  "createNewGroups": true
}

Merge Groups

Combine multiple groups:

// Merge groups manually
POST /api/groups/merge
{
  "groupIds": ["group1", "group2", "group3"],
  "newFingerprint": "custom-merged-group"
}

Next Steps

Filtering & Search

Advanced filtering and search techniques

Analytics

Analyze error trends and patterns

AI Integration

Use AI to analyze grouped errors

Dashboard Features

Explore the error groups dashboard