release: WRNexusJS 0.7.0

packages/observability/src/metrics.ts

@@ -0,0 +1,81 @@
+export type MetricLabels = Record<string, string | number | boolean>;
+
+export interface MetricPoint {
+  name: string;
+  type: "counter" | "gauge" | "histogram";
+  value: number;
+  count?: number;
+  sum?: number;
+  min?: number;
+  max?: number;
+  labels: MetricLabels;
+  timestamp: number;
+}
+
+function labelKey(labels: MetricLabels): string {
+  return Object.entries(labels)
+    .sort(([a], [b]) => (a < b ? -1 : a > b ? 1 : 0))
+    .map(([key, value]) => `${key}=${String(value)}`)
+    .join(",");
+}
+
+interface StoredMetric extends MetricPoint {
+  key: string;
+}
+
+export class MetricsRegistry {
+  private points = new Map<string, StoredMetric>();
+  constructor(private readonly clock: () => number = Date.now) {}
+
+  increment(name: string, value = 1, labels: MetricLabels = {}): void {
+    const key = `counter:${name}:${labelKey(labels)}`;
+    const current = this.points.get(key);
+    this.points.set(key, {
+      key,
+      name,
+      type: "counter",
+      value: (current?.value ?? 0) + value,
+      labels: { ...labels },
+      timestamp: this.clock(),
+    });
+  }
+
+  gauge(name: string, value: number, labels: MetricLabels = {}): void {
+    const key = `gauge:${name}:${labelKey(labels)}`;
+    this.points.set(key, {
+      key,
+      name,
+      type: "gauge",
+      value,
+      labels: { ...labels },
+      timestamp: this.clock(),
+    });
+  }
+
+  observe(name: string, value: number, labels: MetricLabels = {}): void {
+    const key = `histogram:${name}:${labelKey(labels)}`;
+    const current = this.points.get(key);
+    const count = (current?.count ?? 0) + 1;
+    const sum = (current?.sum ?? 0) + value;
+    this.points.set(key, {
+      key,
+      name,
+      type: "histogram",
+      value: sum / count,
+      count,
+      sum,
+      min: current?.min === undefined ? value : Math.min(current.min, value),
+      max: current?.max === undefined ? value : Math.max(current.max, value),
+      labels: { ...labels },
+      timestamp: this.clock(),
+    });
+  }
+
+  snapshot(): MetricPoint[] {
+    return [...this.points.values()].map(({ key: _key, ...point }) => ({ ...point }));
+  }
+
+  reset(): void {
+    this.points.clear();
+  }
+}