Changelog

March 14, 2026 · View on GitHub

All notable changes to Den are documented in this file.

[v0.0.6] — 2026-03-14

Memory pressure monitoring — Real-time host memory tracking with 5-level pressure system (Normal → Warning → High → Critical → Emergency)
Dynamic memory throttling — Automatic per-container memory.high (cgroup v2) adjustment based on host pressure level
Pressure-aware sandbox creation — Rejects new sandboxes at Critical/Emergency pressure (HTTP 503)
Hysteresis / debounce — Pressure level changes require 2 consecutive readings to prevent flapping
Resource status API — GET /api/v1/resources endpoint returning host memory, sandbox count, and pressure info
Platform abstraction — MemoryBackend interface with Linux (/proc/meminfo + cgroup) and macOS (sysctl + Docker API) implementations
Direct cgroup v2 writes — Linux containers get memory.high set via direct cgroup file write (sub-ms), Docker API fallback
Pressure drop recovery — Memory limits automatically removed when pressure returns to Normal/Warning
OOM score management — Dynamic OOM score adjustment for container processes (Linux only)
PID ≤ 1 protection — Refuses to modify OOM score for init/host processes
Double-start protection — sync.Once guard on PressureMonitor.Start()
Panic recovery — All pressure monitor goroutine operations wrapped in safeSample() with recover
ResourceConfig — Top-level resource: config section with configurable thresholds, intervals, and overcommit ratios

Shutdown sequence — PressureMonitor.Stop() now blocks until goroutine finishes via doneCh (prevents send-on-closed-channel panic)
Container limit updates — Single sync.Map.Range() pass instead of two (fixes TOCTOU race)
Memory limit strategy — Direct cgroup write first, Docker API fallback (was reversed)
Threshold configuration — Resource handler uses engine config thresholds instead of hardcoded values

Hysteresis bypass — CurrentEvent().Level now returns confirmed (debounced) level, not raw measurement
memoryHigh=0 handling — Writing "max" to cgroup v2 correctly removes limits (was no-op)