All files / src/platform/observability/services metrics.service.ts

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import { Injectable, Logger } from '@nestjs/common';
 
export interface MetricPoint {
  name: string;
  value: number;
  labels?: Record<string, string>;
  timestamp: Date;
}
 
@Injectable()
export class MetricsService {
  private readonly logger = new Logger(MetricsService.name);
 
  private readonly counters = new Map<string, number>();
  private readonly gauges = new Map<string, number>();
  private readonly histograms = new Map<string, number[]>();
 
  incrementCounter(
    name: string,
    labels?: Record<string, string>,
    amount = 1,
  ): void {
    const key = this.buildKey(name, labels);
    this.counters.set(key, (this.counters.get(key) ?? 0) + amount);
  }
 
  setGauge(name: string, value: number, labels?: Record<string, string>): void {
    const key = this.buildKey(name, labels);
    this.gauges.set(key, value);
  }
 
  recordHistogram(
    name: string,
    value: number,
    labels?: Record<string, string>,
  ): void {
    const key = this.buildKey(name, labels);
    const arr = this.histograms.get(key) ?? [];
    arr.push(value);
    if (arr.length > 10000) arr.shift(); // sliding window
    this.histograms.set(key, arr);
  }
 
  getCounter(name: string, labels?: Record<string, string>): number {
    return this.counters.get(this.buildKey(name, labels)) ?? 0;
  }
 
  getGauge(name: string, labels?: Record<string, string>): number {
    return this.gauges.get(this.buildKey(name, labels)) ?? 0;
  }
 
  getHistogramStats(
    name: string,
    labels?: Record<string, string>,
  ): {
    count: number;
    avg: number;
    p50: number;
    p95: number;
    p99: number;
    max: number;
  } | null {
    const arr = this.histograms.get(this.buildKey(name, labels));
    if (!arr || arr.length === 0) return null;
    const sorted = [...arr].sort((a, b) => a - b);
    const count = sorted.length;
    const avg = sorted.reduce((a, b) => a + b, 0) / count;
    return {
      count,
      avg: Math.round(avg * 100) / 100,
      p50: sorted[Math.floor(count * 0.5)],
      p95: sorted[Math.floor(count * 0.95)],
      p99: sorted[Math.floor(count * 0.99)],
      max: sorted[count - 1],
    };
  }
 
  getAllMetrics(): {
    counters: Record<string, number>;
    gauges: Record<string, number>;
  } {
    return {
      counters: Object.fromEntries(this.counters),
      gauges: Object.fromEntries(this.gauges),
    };
  }
 
  private buildKey(name: string, labels?: Record<string, string>): string {
    if (!labels || Object.keys(labels).length === 0) return name;
    const labelStr = Object.entries(labels)
      .sort(([a], [b]) => a.localeCompare(b))
      .map(([k, v]) => `${k}=${v}`)
      .join(',');
    return `${name}{${labelStr}}`;
  }
}