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* Performance Monitoring Utilities
*
* **Intelligence Perspective:** Performance metrics enable operational intelligence
* on system health—critical for maintaining reliable intelligence product delivery.
*
* **Business Perspective:** P95 latency targets (<200ms) directly impact customer
* satisfaction and SLA compliance for premium API tier customers.
*
* **Marketing Perspective:** Sub-200ms response times are a key performance claim
* for developer marketing and competitive positioning against alternatives.
*
* ISMS Policy: PE-001 (Performance Standards), MO-001 (Monitoring)
*
* Provides performance monitoring and metrics collection for:
* - Operation duration tracking
* - Percentile calculations (p50, p95, p99)
* - Performance baseline validation
* - Alerting on degradation
*
* @see https://github.com/Hack23/ISMS-PUBLIC/blob/main/Secure_Development_Policy.md
*/
/**
* Performance metric statistics
*/
export interface PerformanceStats {
/** Median (50th percentile) duration in milliseconds */
p50: number;
/** 95th percentile duration in milliseconds */
p95: number;
/** 99th percentile duration in milliseconds */
p99: number;
/** Average duration in milliseconds */
avg: number;
/** Minimum duration in milliseconds */
min: number;
/** Maximum duration in milliseconds */
max: number;
/** Total number of measurements */
count: number;
}
/**
* Warning thresholds for performance alerting.
*
* Operations that exceed these thresholds should be flagged for
* review in dashboards or log-based alerting rules.
*/
export interface PerformanceThresholds {
/** Warn when p95 exceeds this value (milliseconds) */
p95WarningMs: number;
/** Warn when p99 exceeds this value (milliseconds) */
p99WarningMs: number;
/** Warn when average exceeds this value (milliseconds) */
avgWarningMs?: number;
}
/**
* Default performance thresholds aligned with the ISMS PE-001 standard
* (target: p95 < 200 ms for cached operations).
*/
export const DEFAULT_PERFORMANCE_THRESHOLDS: PerformanceThresholds = {
p95WarningMs: 200,
p99WarningMs: 500,
avgWarningMs: 150,
} as const;
/**
* Performance monitor for tracking operation metrics
*
* Tracks duration of operations and provides statistical analysis.
* Useful for identifying performance regressions and bottlenecks.
*
* @example
* ```typescript
* const monitor = new PerformanceMonitor();
*
* // Record operation durations
* monitor.recordDuration('api_call', 150);
* monitor.recordDuration('api_call', 200);
*
* // Get statistics
* const stats = monitor.getStats('api_call');
* console.log(`p95: ${stats.p95}ms`);
* ```
*/
export class PerformanceMonitor {
private readonly metrics = new Map<string, number[]>();
private readonly maxSamples: number;
/**
* Creates a new performance monitor.
*
* @param maxSamples - Maximum number of duration samples to retain per
* operation name. Older samples are evicted when the limit is reached
* (sliding window). Default: `1000`.
* @throws {RangeError} If `maxSamples` is not a positive finite integer
*
* @example
* ```typescript
* const monitor = new PerformanceMonitor(500);
* ```
*
* @since 0.8.0
*/
constructor(maxSamples = 1000) {
if (!Number.isFinite(maxSamples) || !Number.isInteger(maxSamples) || maxSamples <= 0) {
throw new RangeError('maxSamples must be a positive integer');
}
this.maxSamples = maxSamples;
}
/**
* Records a duration sample for the named operation.
*
* When the number of stored samples reaches `maxSamples`, the oldest
* entries are evicted in bulk (sliding window). Use {@link getStats} to
* retrieve aggregated statistics after recording samples.
*
* @param operation - Unique operation name / identifier (e.g., `'ep_api_call'`)
* @param durationMs - Observed duration in milliseconds (should be ≥ 0)
* @throws {TypeError} If `operation` is not a string
*
* @example
* ```typescript
* const start = performance.now();
* await doWork();
* monitor.recordDuration('work', performance.now() - start);
* ```
*
* @since 0.8.0
*/
recordDuration(operation: string, durationMs: number): void {
let durations = this.metrics.get(operation);
if (!durations) {
durations = [];
this.metrics.set(operation, durations);
}
durations.push(durationMs);
// Limit number of samples to prevent unbounded memory growth
// Trim the oldest entries in-place using splice instead of repeatedly calling shift()
// to keep the most recent samples while avoiding extra array allocations
if (durations.length > this.maxSamples) {
const overflow = durations.length - this.maxSamples;
durations.splice(0, overflow);
}
}
/**
* Returns aggregated performance statistics for a named operation.
*
* Calculates percentiles (p50 / p95 / p99), average, min, and max from
* the stored duration samples. Returns `null` when no samples have been
* recorded for the operation yet.
*
* @param operation - Operation name / identifier to query
* @returns {@link PerformanceStats} object, or `null` if no data exists
* @throws {TypeError} If `operation` is not a string
*
* @example
* ```typescript
* const stats = monitor.getStats('api_call');
* if (stats && stats.p95 > 1000) {
* console.warn('API calls are slow (p95 > 1s)');
* }
* ```
*
* @since 0.8.0
*/
getStats(operation: string): PerformanceStats | null {
const durations = this.metrics.get(operation);
if (!durations || durations.length === 0) {
return null;
}
// Sort durations for percentile calculation
const sorted = [...durations].sort((a, b) => a - b);
const count = sorted.length;
// Calculate statistics
const sum = sorted.reduce((acc, val) => acc + val, 0);
const min = sorted[0];
const max = sorted[count - 1];
Iif (min === undefined || max === undefined) {
return null;
}
return {
p50: this.percentile(sorted, 0.5),
p95: this.percentile(sorted, 0.95),
p99: this.percentile(sorted, 0.99),
avg: sum / count,
min,
max,
count
};
}
/**
* Calculate percentile from sorted array
*
* Uses linear interpolation for more accurate percentile calculation
*
* @param sorted - Sorted array of numbers
* @param p - Percentile (0.0 to 1.0)
* @returns Value at the specified percentile
*
* @internal
*/
private percentile(sorted: number[], p: number): number {
Iif (sorted.length === 0) return 0;
const first = sorted[0];
if (sorted.length === 1 && first !== undefined) return first;
const index = (sorted.length - 1) * p;
const lower = Math.floor(index);
const upper = Math.ceil(index);
const weight = index % 1;
if (lower === upper) {
return sorted[lower] ?? 0;
}
const lowerValue = sorted[lower];
const upperValue = sorted[upper];
Iif (lowerValue === undefined || upperValue === undefined) {
return 0;
}
return lowerValue * (1 - weight) + upperValue * weight;
}
/**
* Returns all operation names currently being tracked.
*
* @returns Array of operation name strings, in insertion order
*
* @example
* ```typescript
* const operations = monitor.getOperations();
* operations.forEach(op => {
* const stats = monitor.getStats(op);
* console.log(`${op}: p95=${stats?.p95}ms`);
* });
* ```
*
* @since 0.8.0
*/
getOperations(): string[] {
return Array.from(this.metrics.keys());
}
/**
* Clears all recorded duration samples for every tracked operation.
*
* Useful for resetting state between test cases or at the start of a new
* monitoring window.
*
* @example
* ```typescript
* // Reset metrics after each test
* afterEach(() => {
* monitor.clear();
* });
* ```
*
* @since 0.8.0
*/
clear(): void {
this.metrics.clear();
}
/**
* Clears recorded duration samples for a single operation.
*
* @param operation - Operation name whose samples should be discarded
*
* @example
* ```typescript
* monitor.clearOperation('api_call');
* ```
*
* @since 0.8.0
*/
clearOperation(operation: string): void {
this.metrics.delete(operation);
}
}
/**
* Execute an async function and track its performance
*
* Automatically records the duration of the operation in the
* provided performance monitor.
*
* @template T - Return type of the function
* @param monitor - Performance monitor to record the duration in
* @param operation - Operation name for tracking (e.g., `'fetch_meps'`)
* @param fn - Async function to execute and measure
* @returns Promise that resolves with the function result
* @throws Re-throws any error thrown by `fn` after recording the duration
*
* @example
* ```typescript
* const monitor = new PerformanceMonitor();
*
* const result = await withPerformanceTracking(
* monitor,
* 'fetch_meps',
* async () => {
* return await client.getMEPs({ limit: 100 });
* }
* );
* ```
*
* @since 0.8.0
*/
export async function withPerformanceTracking<T>(
monitor: PerformanceMonitor,
operation: string,
fn: () => Promise<T>
): Promise<T> {
const start = performance.now();
try {
return await fn();
} finally {
const duration = performance.now() - start;
monitor.recordDuration(operation, duration);
}
}
/**
* Global performance monitor instance
*
* Shared instance for application-wide performance tracking.
* Use this for convenience when you don't need isolated monitoring.
*
* @example
* ```typescript
* import { performanceMonitor } from './utils/performance.js';
*
* // Record duration
* performanceMonitor.recordDuration('api_call', 150);
*
* // Get statistics
* const stats = performanceMonitor.getStats('api_call');
* ```
*/
export const performanceMonitor = new PerformanceMonitor();
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