@dudousxd/nestjs-telescope/dist/rollup/aggregate-deltas.js

Laravel Telescope-style observability console for NestJS — core: watchers, recorder, correlation, SQLite store, headless API.

import { emptyHistogram, floorToBucket, incrementHistogram, } from './rollup-store.js';
/**
 * Folds a batch of entries into additive rollup deltas, grouped by
 * `(type, floorToBucket(createdAt))`. Pure & deterministic:
 * - `count` = number of entries in the group,
 * - `sum`   = Σ durationMs (null treated as 0),
 * - `max`   = max durationMs (0 when every entry's durationMs is null),
 * - `histogram` = fixed-size latency-bucket counts; ONLY entries with a non-null
 *   `durationMs` increment a cell (null durations contribute to count/sum/max as
 *   before but NOT to the histogram). Memory-safe: a small fixed-length integer
 *   array per group, never any retained entry references.
 */
export function aggregateDeltas(entries) {
    const groups = new Map();
    for (const entry of entries) {
        const bucketStart = floorToBucket(entry.createdAt.getTime());
        const key = `${entry.type}|${bucketStart}`;
        const duration = entry.durationMs ?? 0;
        const existing = groups.get(key);
        if (existing === undefined) {
            const histogram = emptyHistogram();
            if (entry.durationMs !== null) {
                incrementHistogram(histogram, entry.durationMs);
            }
            groups.set(key, {
                metric: entry.type,
                bucketStart,
                count: 1,
                sum: duration,
                max: duration,
                histogram,
            });
        }
        else {
            existing.count += 1;
            existing.sum += duration;
            existing.max = Math.max(existing.max, duration);
            if (entry.durationMs !== null) {
                incrementHistogram(existing.histogram, entry.durationMs);
            }
        }
    }
    return [...groups.values()];
}
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