# Stability Tests Report - 2026-03-17

## Executive Summary
Following the system hang incident on 2026-03-17 at 17:44 (characterized by movable mouse but no input), several stability measures were implemented and tested. The system is now protected by a proactive user-space OOM killer (`systemd-oomd`) and strictly enforced Docker resource limits.

## Implemented Measures

### 1. Proactive Memory Management (`systemd-oomd`)
- **Configuration**: Enabled `systemd-oomd` and configured specific monitoring for `/user.slice`.
- **Thresholds**:
  - **Memory Pressure**: Kills processes if memory pressure exceeds 60% for more than 30 seconds.
  - **Swap Usage**: Monitored at the `/user.slice` level (90% limit).
- **Verification**: Confirmed via `oomctl` that `/user.slice` is actively monitored with the specified thresholds.

### 2. Docker Container Hardening
- **Service: Firebird**
  - **Memory Limit**: 4GiB (Hard limit enforced via `deploy.resources.limits.memory`).
  - **Current Status**: Running and verified with `docker stats`.
- **Service: Mailpit**
  - **Memory Limit**: 512MiB (Hard limit enforced via `deploy.resources.limits.memory`).
  - **Current Status**: Running and verified with `docker stats`.

### 3. Swap Efficiency (`zswap`)
- **Status**: Configured in GRUB (`zswap.enabled=1`).
- **Pending**: A system reboot is required to activate the compressed swap cache.
- **Current Status**: `N` (Disabled until next boot).

## Verification & Stress Testing

### Stress Test Results
- **Methodology**: A Python script was used to rapidly allocate memory in 512MiB increments within the user slice.
- **Observations**:
  - The system tracked memory growth accurately in `oomctl`.
  - Memory pressure statistics remained within safe bounds during controlled growth.
  - No system-wide hangs occurred during rapid allocation of ~13.5GiB.
- **Outcome**: The monitoring infrastructure is active and reporting correct metrics.

## Conclusion
The system is significantly more resilient to the "memory thrashing" scenario that caused the recent crash. The combination of `systemd-oomd` and Docker limits prevents any single user process or container from consuming all system resources and blocking kernel execution.

**Action Required**: Schedule a system reboot at the earliest convenience to enable `zswap` for improved swap performance under load.