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* PerformanceAnalyzer - Detect performance bottlenecks and anti-patterns
* Identifies: Nested loops, sync I/O, N+1 queries, memory leaks, blocking operations
*/
class PerformanceAnalyzer {
constructor() {
this.version = '1.0.0';
}
/**
* Analyze performance patterns
* @param {Array} files - All files with content
* @returns {Object} Performance analysis
*/
analyze(files) {
const nestedLoops = this.detectNestedLoops(files);
const syncIO = this.detectSynchronousIO(files);
const nPlusOne = this.detectNPlusOneQueries(files);
const memoryLeaks = this.detectMemoryLeakPatterns(files);
const blockingOps = this.detectBlockingOperations(files);
const inefficientRegex = this.detectInefficientRegex(files);
const hotspots = this.identifyHotspots(nestedLoops, syncIO, nPlusOne, memoryLeaks, blockingOps);
return {
nestedLoops,
synchronousIO: syncIO,
nPlusOneQueries: nPlusOne,
memoryLeaks,
blockingOperations: blockingOps,
inefficientRegex,
hotspots,
summary: this.generateSummary(nestedLoops, syncIO, nPlusOne, memoryLeaks, blockingOps, inefficientRegex)
};
}
/**
* Detect nested loops (O(n²) or worse complexity)
*/
detectNestedLoops(files) {
const issues = [];
files.forEach(file => {
if (!file.content) return;
const lines = file.content.split('\n');
const loopStack = [];
lines.forEach((line, lineIndex) => {
const trimmed = line.trim();
// Detect loop start
if (/\b(?:for|while|forEach|map|filter|reduce)\s*\(/.test(trimmed)) {
loopStack.push({
type: this.identifyLoopType(trimmed),
line: lineIndex + 1,
depth: loopStack.length + 1
});
}
// Detect loop end (simplified - check closing braces)
if (trimmed === '}' && loopStack.length > 0) {
const loop = loopStack.pop();
// Report nested loops
if (loop.depth >= 2) {
const complexity = this.calculateLoopComplexity(loop.depth);
issues.push({
type: 'NESTED_LOOP',
file: file.filePath,
line: loop.line,
depth: loop.depth,
complexity,
severity: loop.depth >= 3 ? 'CRITICAL' : 'HIGH',
message: `Nested loop with depth ${loop.depth} (${complexity} complexity)`,
recommendation: 'Consider using hash maps, caching, or algorithmic optimization',
performanceImpact: this.estimatePerformanceImpact(loop.depth)
});
}
}
});
});
return issues;
}
/**
* Identify loop type
*/
identifyLoopType(line) {
if (/\bfor\s*\(/.test(line)) return 'for';
if (/\bwhile\s*\(/.test(line)) return 'while';
if (/\bforEach\s*\(/.test(line)) return 'forEach';
if (/\bmap\s*\(/.test(line)) return 'map';
if (/\bfilter\s*\(/.test(line)) return 'filter';
if (/\breduce\s*\(/.test(line)) return 'reduce';
return 'loop';
}
/**
* Calculate loop complexity notation
*/
calculateLoopComplexity(depth) {
const notations = ['O(n)', 'O(n²)', 'O(n³)', 'O(n⁴)', 'O(n⁵)'];
return notations[depth - 1] || `O(n^${depth})`;
}
/**
* Estimate performance impact
*/
estimatePerformanceImpact(depth) {
const impacts = {
1: 'LINEAR - Acceptable',
2: 'QUADRATIC - May slow with large datasets',
3: 'CUBIC - Critical performance issue',
4: 'POLYNOMIAL - Severe performance bottleneck'
};
return impacts[depth] || 'EXPONENTIAL - Catastrophic performance';
}
/**
* Detect synchronous I/O in async context
*/
detectSynchronousIO(files) {
const issues = [];
const syncPatterns = [
{ pattern: /fs\.readFileSync\(/g, api: 'fs.readFileSync', alternative: 'fs.promises.readFile' },
{ pattern: /fs\.writeFileSync\(/g, api: 'fs.writeFileSync', alternative: 'fs.promises.writeFile' },
{ pattern: /fs\.readdirSync\(/g, api: 'fs.readdirSync', alternative: 'fs.promises.readdir' },
{ pattern: /fs\.statSync\(/g, api: 'fs.statSync', alternative: 'fs.promises.stat' },
{ pattern: /child_process\.execSync\(/g, api: 'child_process.execSync', alternative: 'child_process.exec with promises' },
{ pattern: /child_process\.spawnSync\(/g, api: 'child_process.spawnSync', alternative: 'child_process.spawn' },
{ pattern: /crypto\.pbkdf2Sync\(/g, api: 'crypto.pbkdf2Sync', alternative: 'crypto.pbkdf2 (async)' }
];
files.forEach(file => {
if (!file.content) return;
const lines = file.content.split('\n');
const isAsync = file.content.includes('async ') || file.content.includes('await ');
lines.forEach((line, lineIndex) => {
syncPatterns.forEach(({ pattern, api, alternative }) => {
if (pattern.test(line)) {
issues.push({
type: 'SYNCHRONOUS_IO',
file: file.filePath,
line: lineIndex + 1,
api,
severity: isAsync ? 'CRITICAL' : 'HIGH',
message: `Synchronous I/O operation ${api} ${isAsync ? 'in async function' : ''}`,
recommendation: `Replace with ${alternative}`,
performanceImpact: 'Blocks event loop, reduces throughput'
});
}
pattern.lastIndex = 0;
});
});
});
return issues;
}
/**
* Detect N+1 query patterns
*/
detectNPlusOneQueries(files) {
const issues = [];
files.forEach(file => {
if (!file.content) return;
const lines = file.content.split('\n');
// Pattern: Query in loop
let inLoop = false;
let loopStartLine = 0;
lines.forEach((line, lineIndex) => {
// Detect loop
if (/\b(?:for|while|forEach|map)\s*\(/.test(line)) {
inLoop = true;
loopStartLine = lineIndex + 1;
}
// Detect query inside loop
if (inLoop) {
const queryPatterns = [
/\.find\(/,
/\.findOne\(/,
/\.findById\(/,
/\.get\(/,
/\.query\(/,
/SELECT\s+.*FROM/i,
/await\s+\w+\.(find|get|query)/
];
if (queryPatterns.some(pattern => pattern.test(line))) {
issues.push({
type: 'N_PLUS_ONE_QUERY',
file: file.filePath,
line: lineIndex + 1,
loopLine: loopStartLine,
severity: 'CRITICAL',
message: 'Database query inside loop (N+1 problem)',
recommendation: 'Use batch loading, joins, or eager loading (e.g., .populate(), .include())',
performanceImpact: 'Exponential database queries, severe performance degradation'
});
}
}
// Detect loop end
if (line.trim() === '}' && inLoop) {
inLoop = false;
}
});
});
return issues;
}
/**
* Detect memory leak patterns
*/
detectMemoryLeakPatterns(files) {
const issues = [];
files.forEach(file => {
if (!file.content) return;
const lines = file.content.split('\n');
lines.forEach((line, lineIndex) => {
// Event listeners without removal
if (/\.addEventListener\(|\.on\(/.test(line)) {
const hasRemoveListener = file.content.includes('removeEventListener') ||
file.content.includes('.off(') ||
file.content.includes('cleanup');
if (!hasRemoveListener) {
issues.push({
type: 'MEMORY_LEAK_EVENT_LISTENER',
file: file.filePath,
line: lineIndex + 1,
severity: 'HIGH',
message: 'Event listener added without cleanup',
recommendation: 'Add removeEventListener in cleanup/unmount',
performanceImpact: 'Memory accumulation over time'
});
}
}
// Timers without clearing
if (/setInterval\(|setTimeout\(/.test(line)) {
const hasClearTimer = file.content.includes('clearInterval') ||
file.content.includes('clearTimeout');
if (!hasClearTimer) {
issues.push({
type: 'MEMORY_LEAK_TIMER',
file: file.filePath,
line: lineIndex + 1,
severity: 'HIGH',
message: 'Timer created without cleanup',
recommendation: 'Clear timer in cleanup function',
performanceImpact: 'Memory and CPU accumulation'
});
}
}
// Closures holding large objects
if (/function\s*\([^)]*\)\s*{[\s\S]*?const\s+\w+\s*=\s*\[/.test(line)) {
issues.push({
type: 'MEMORY_LEAK_CLOSURE',
file: file.filePath,
line: lineIndex + 1,
severity: 'MEDIUM',
message: 'Closure may capture large data structures',
recommendation: 'Review closure scope, release references when done',
performanceImpact: 'Prevents garbage collection'
});
}
// Unclosed resources
const resourcePatterns = [
{ pattern: /new\s+FileReader\(/, cleanup: 'abort()' },
{ pattern: /fs\.createReadStream\(/, cleanup: '.close()' },
{ pattern: /new\s+WebSocket\(/, cleanup: '.close()' },
{ pattern: /database\.connect\(/, cleanup: '.disconnect()' }
];
resourcePatterns.forEach(({ pattern, cleanup }) => {
if (pattern.test(line) && !file.content.includes(cleanup)) {
issues.push({
type: 'UNCLOSED_RESOURCE',
file: file.filePath,
line: lineIndex + 1,
severity: 'HIGH',
message: 'Resource opened without explicit cleanup',
recommendation: `Ensure ${cleanup} is called`,
performanceImpact: 'Resource exhaustion, file descriptor leaks'
});
}
});
});
});
return issues;
}
/**
* Detect blocking operations
*/
detectBlockingOperations(files) {
const issues = [];
const blockingPatterns = [
{ pattern: /while\s*\(\s*true\s*\)/g, name: 'Infinite loop', severity: 'CRITICAL' },
{ pattern: /for\s*\(\s*;\s*;\s*\)/g, name: 'Infinite for loop', severity: 'CRITICAL' },
{ pattern: /\.sort\(\s*\)/g, name: 'Array sort (O(n log n))', severity: 'MEDIUM' },
{ pattern: /JSON\.parse\(/g, name: 'JSON.parse (synchronous)', severity: 'LOW' },
{ pattern: /JSON\.stringify\(/g, name: 'JSON.stringify (synchronous)', severity: 'LOW' },
{ pattern: /crypto\.pbkdf2Sync\(/g, name: 'Synchronous crypto operation', severity: 'HIGH' },
{ pattern: /\.match\([^)]{50,}\)/g, name: 'Complex regex match', severity: 'MEDIUM' }
];
files.forEach(file => {
if (!file.content) return;
const lines = file.content.split('\n');
lines.forEach((line, lineIndex) => {
blockingPatterns.forEach(({ pattern, name, severity }) => {
if (pattern.test(line)) {
issues.push({
type: 'BLOCKING_OPERATION',
file: file.filePath,
line: lineIndex + 1,
operation: name,
severity,
message: `Blocking operation: ${name}`,
recommendation: this.getBlockingRecommendation(name),
performanceImpact: 'Blocks event loop, reduces responsiveness'
});
}
pattern.lastIndex = 0;
});
});
});
return issues;
}
/**
* Get recommendation for blocking operation
*/
getBlockingRecommendation(operation) {
const recommendations = {
'Infinite loop': 'Add exit condition or use worker thread',
'Infinite for loop': 'Add proper loop termination',
'Array sort (O(n log n))': 'Consider pre-sorting or using indexed structure',
'JSON.parse (synchronous)': 'For large JSON, consider streaming parser',
'JSON.stringify (synchronous)': 'For large objects, consider streaming serializer',
'Synchronous crypto operation': 'Use async version',
'Complex regex match': 'Simplify regex or use multiple simpler patterns'
};
return recommendations[operation] || 'Optimize or make async';
}
/**
* Detect inefficient regex patterns
*/
detectInefficientRegex(files) {
const issues = [];
files.forEach(file => {
if (!file.content) return;
const lines = file.content.split('\n');
lines.forEach((line, lineIndex) => {
// Find regex patterns
const regexMatches = line.match(/\/([^\/]+)\/[gimuy]*/g) || [];
regexMatches.forEach(regexStr => {
// Detect catastrophic backtracking patterns
const catastrophicPatterns = [
{ pattern: /\(\.\*\)\+|\(\.\+\)\+/, issue: 'Nested quantifiers' },
{ pattern: /\([^)]*\*[^)]*\)\*/, issue: 'Nested star operators' },
{ pattern: /\([^)]*\+[^)]*\)\+/, issue: 'Nested plus operators' },
{ pattern: /\([^|]+\|[^|]+\)\+/, issue: 'Alternation with quantifier' }
];
catastrophicPatterns.forEach(({ pattern, issue }) => {
if (pattern.test(regexStr)) {
issues.push({
type: 'CATASTROPHIC_BACKTRACKING',
file: file.filePath,
line: lineIndex + 1,
regex: regexStr,
issue,
severity: 'CRITICAL',
message: `Regex with potential catastrophic backtracking: ${issue}`,
recommendation: 'Simplify regex, use atomic groups, or non-backtracking patterns',
performanceImpact: 'Exponential time complexity, can hang application'
});
}
});
// Detect overly complex regex
if (regexStr.length > 100) {
issues.push({
type: 'COMPLEX_REGEX',
file: file.filePath,
line: lineIndex + 1,
regex: regexStr.substring(0, 50) + '...',
severity: 'MEDIUM',
message: 'Overly complex regex pattern',
recommendation: 'Break into smaller patterns or use parser',
performanceImpact: 'Slow pattern matching'
});
}
});
});
});
return issues;
}
/**
* Identify performance hotspots
*/
identifyHotspots(nestedLoops, syncIO, nPlusOne, memoryLeaks, blockingOps) {
const allIssues = [
...nestedLoops,
...syncIO,
...nPlusOne,
...memoryLeaks,
...blockingOps
];
// Group by file
const byFile = {};
allIssues.forEach(issue => {
if (!byFile[issue.file]) {
byFile[issue.file] = {
file: issue.file,
issues: [],
criticalCount: 0,
highCount: 0,
score: 0
};
}
byFile[issue.file].issues.push(issue);
if (issue.severity === 'CRITICAL') {
byFile[issue.file].criticalCount++;
byFile[issue.file].score += 10;
} else if (issue.severity === 'HIGH') {
byFile[issue.file].highCount++;
byFile[issue.file].score += 5;
} else {
byFile[issue.file].score += 1;
}
});
// Top 10 hotspots
return Object.values(byFile)
.sort((a, b) => b.score - a.score)
.slice(0, 10)
.map(hotspot => ({
...hotspot,
priority: hotspot.criticalCount > 0 ? 'CRITICAL' : hotspot.highCount > 2 ? 'HIGH' : 'MEDIUM',
recommendation: this.generateHotspotRecommendation(hotspot)
}));
}
/**
* Generate hotspot recommendation
*/
generateHotspotRecommendation(hotspot) {
const recommendations = [];
if (hotspot.criticalCount > 0) {
recommendations.push(`Address ${hotspot.criticalCount} critical performance issues immediately`);
}
const types = hotspot.issues.map(i => i.type);
if (types.includes('NESTED_LOOP')) {
recommendations.push('Optimize nested loops with better algorithms or caching');
}
if (types.includes('N_PLUS_ONE_QUERY')) {
recommendations.push('Implement batch loading or eager loading for database queries');
}
if (types.includes('SYNCHRONOUS_IO')) {
recommendations.push('Convert synchronous I/O to async operations');
}
return recommendations.length > 0 ? recommendations : ['Review and optimize performance patterns'];
}
/**
* Generate summary
*/
generateSummary(nestedLoops, syncIO, nPlusOne, memoryLeaks, blockingOps, inefficientRegex) {
return {
totalIssues: nestedLoops.length + syncIO.length + nPlusOne.length + memoryLeaks.length + blockingOps.length + inefficientRegex.length,
nestedLoops: nestedLoops.length,
synchronousIO: syncIO.length,
nPlusOneQueries: nPlusOne.length,
memoryLeaks: memoryLeaks.length,
blockingOperations: blockingOps.length,
inefficientRegex: inefficientRegex.length,
criticalIssues: [
...nestedLoops.filter(i => i.severity === 'CRITICAL'),
...syncIO.filter(i => i.severity === 'CRITICAL'),
...nPlusOne,
...inefficientRegex.filter(i => i.severity === 'CRITICAL')
].length
};
}
}
module.exports = PerformanceAnalyzer;
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