Add Redis rolling stats for flow packets and z-score driven classifiers

services/compute/src/rolling-stats.ts

@@ -0,0 +1,74 @@
+import { createClient } from "redis";
+
+export type RollingStatsConfig = {
+  windowSize: number;
+  ttlSeconds: number;
+};
+
+export type RollingSnapshot = {
+  baselineCount: number;
+  mean: number;
+  stddev: number;
+  zscore: number;
+};
+
+const toNumbers = (values: string[]): number[] => {
+  return values
+    .map((value) => Number(value))
+    .filter((value) => Number.isFinite(value));
+};
+
+export const computeStats = (values: number[]): { mean: number; stddev: number; count: number } => {
+  const count = values.length;
+  if (count === 0) {
+    return { mean: 0, stddev: 0, count: 0 };
+  }
+
+  const mean = values.reduce((sum, value) => sum + value, 0) / count;
+  const variance =
+    values.reduce((sum, value) => {
+      const delta = value - mean;
+      return sum + delta * delta;
+    }, 0) / count;
+
+  return { mean, stddev: Math.sqrt(variance), count };
+};
+
+export const computeSnapshot = (baseline: number[], value: number): RollingSnapshot => {
+  const stats = computeStats(baseline);
+  const zscore = stats.stddev === 0 ? 0 : (value - stats.mean) / stats.stddev;
+  return {
+    baselineCount: stats.count,
+    mean: stats.mean,
+    stddev: stats.stddev,
+    zscore
+  };
+};
+
+export const createRedisClient = (url: string) => {
+  return createClient({ url });
+};
+
+export const updateRollingStats = async (
+  client: ReturnType<typeof createClient>,
+  key: string,
+  value: number,
+  config: RollingStatsConfig
+): Promise<RollingSnapshot> => {
+  const limit = Math.max(0, config.windowSize - 1);
+  const existing = await client.lRange(key, 0, limit);
+  const baseline = toNumbers(existing);
+  const snapshot = computeSnapshot(baseline, value);
+
+  const multi = client.multi();
+  multi.lPush(key, value.toString());
+  if (config.windowSize > 0) {
+    multi.lTrim(key, 0, config.windowSize - 1);
+  }
+  if (config.ttlSeconds > 0) {
+    multi.expire(key, config.ttlSeconds);
+  }
+  await multi.exec();
+
+  return snapshot;
+};