some research and loose thoughts
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Geir Okkenhaug Jerstad
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research/staggered-update-system.md
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research/staggered-update-system.md
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# Staggered Machine Update and Reboot System Research
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## Overview
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Research into implementing an automated system for updating and rebooting all lab machines in a staggered fashion using Nix, cronjobs, and our existing lab tool infrastructure.
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## Goals
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- Minimize downtime by updating machines in waves
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- Ensure system stability with gradual rollouts
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- Leverage Nix's atomic updates and rollback capabilities
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- Integrate with existing lab tool for orchestration
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- Provide monitoring and failure recovery
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## Architecture Components
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### 1. Update Controller
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- Central orchestrator running on management node
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- Maintains machine groups and update schedules
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- Coordinates staggered execution
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- Monitors update progress and health
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### 2. Machine Groups
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```
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Group 1: Non-critical services (dev environments, testing)
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Group 2: Infrastructure services (monitoring, logging)
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Group 3: Critical services (databases, core applications)
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Group 4: Management nodes (controllers, orchestrators)
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```
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### 3. Nix Integration
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- Use `nixos-rebuild switch` for atomic updates
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- Leverage Nix generations for rollback capability
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- Update channels/flakes before rebuilding
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- Validate configuration before applying
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### 4. Lab Tool Integration
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- Extend lab tool with update management commands
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- Machine inventory and grouping
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- Health check integration
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- Status reporting and logging
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## Implementation Strategy
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### Phase 1: Basic Staggered Updates
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```bash
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# Example workflow per machine group
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lab update prepare --group=dev
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lab update execute --group=dev --wait-for-completion
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lab update verify --group=dev
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lab update prepare --group=infrastructure
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# Continue with next group...
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```
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### Phase 2: Enhanced Orchestration
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- Dependency-aware scheduling
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- Health checks before proceeding to next group
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- Automatic rollback on failures
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- Notification system
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### Phase 3: Advanced Features
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- Blue-green deployments for critical services
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- Canary releases
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- Integration with monitoring systems
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- Custom update policies per service
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## Cronjob Design
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### Master Cron Schedule
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```cron
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# Weekly full system update - Sundays at 2 AM
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0 2 * * 0 /home/geir/Home-lab/scripts/staggered-update.sh
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# Daily security updates for critical machines
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0 3 * * * /home/geir/Home-lab/scripts/security-update.sh --group=critical
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# Health check and cleanup
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0 1 * * * /home/geir/Home-lab/scripts/update-health-check.sh
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```
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### Update Script Structure
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```bash
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#!/usr/bin/env bash
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# staggered-update.sh
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set -euo pipefail
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# Configuration
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GROUPS=("dev" "infrastructure" "critical" "management")
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STAGGER_DELAY=30m
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MAX_PARALLEL=3
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# Log setup
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LOG_DIR="/var/log/lab-updates"
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LOG_FILE="$LOG_DIR/update-$(date +%Y%m%d-%H%M%S).log"
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exec > >(tee -a "$LOG_FILE") 2>&1
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for group in "${GROUPS[@]}"; do
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echo "Starting update for group: $group"
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# Pre-update checks
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lab health-check --group="$group" || {
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echo "Health check failed for $group, skipping"
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continue
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}
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# Update Nix channels/flakes
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lab update prepare --group="$group"
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# Execute updates with parallelism control
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lab update execute --group="$group" --parallel="$MAX_PARALLEL"
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# Verify updates
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lab update verify --group="$group" || {
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echo "Verification failed for $group, initiating rollback"
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lab update rollback --group="$group"
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# Send alert
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lab notify --level=error --message="Update failed for $group, rolled back"
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exit 1
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}
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echo "Group $group updated successfully, waiting $STAGGER_DELAY"
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sleep "$STAGGER_DELAY"
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done
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echo "All groups updated successfully"
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lab notify --level=info --message="Staggered update completed successfully"
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```
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## Nix Configuration Management
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### Centralized Configuration
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```nix
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# /home/geir/Home-lab/nix/update-config.nix
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{
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updateGroups = {
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dev = {
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machines = [ "dev-01" "dev-02" "test-env" ];
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updatePolicy = "aggressive";
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maintenanceWindow = "02:00-06:00";
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allowReboot = true;
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};
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infrastructure = {
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machines = [ "monitor-01" "log-server" "backup-01" ];
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updatePolicy = "conservative";
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maintenanceWindow = "03:00-05:00";
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allowReboot = true;
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dependencies = [ "dev" ];
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};
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critical = {
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machines = [ "db-primary" "web-01" "web-02" ];
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updatePolicy = "manual-approval";
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maintenanceWindow = "04:00-05:00";
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allowReboot = false; # Requires manual reboot
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dependencies = [ "infrastructure" ];
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};
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};
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updateSettings = {
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maxParallel = 3;
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healthCheckTimeout = 300;
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rollbackOnFailure = true;
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notificationChannels = [ "email" "discord" ];
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};
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}
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```
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### Machine-Specific Update Configurations
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```nix
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# On each machine: /etc/nixos/update-config.nix
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{
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services.lab-updater = {
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enable = true;
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group = "infrastructure";
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preUpdateScript = ''
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# Stop non-critical services
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systemctl stop some-service
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'';
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postUpdateScript = ''
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# Restart services and verify
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systemctl start some-service
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curl -f http://localhost:8080/health
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'';
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rollbackScript = ''
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# Custom rollback procedures
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systemctl stop some-service
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nixos-rebuild switch --rollback
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systemctl start some-service
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'';
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};
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}
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```
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## Lab Tool Extensions
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### New Commands
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```bash
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# Update management
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lab update prepare [--group=GROUP] [--machine=MACHINE]
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lab update execute [--group=GROUP] [--parallel=N] [--dry-run]
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lab update verify [--group=GROUP]
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lab update rollback [--group=GROUP] [--to-generation=N]
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lab update status [--group=GROUP]
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# Health and monitoring
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lab health-check [--group=GROUP] [--timeout=SECONDS]
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lab update-history [--group=GROUP] [--days=N]
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lab notify [--level=LEVEL] [--message=MSG] [--channel=CHANNEL]
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# Configuration
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lab update-config show [--group=GROUP]
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lab update-config set [--group=GROUP] [--key=KEY] [--value=VALUE]
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```
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### Integration Points
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```python
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# lab/commands/update.py
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class UpdateCommand:
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def prepare(self, group=None, machine=None):
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"""Prepare machines for updates"""
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# Update Nix channels/flakes
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# Pre-update health checks
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# Download packages
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def execute(self, group=None, parallel=1, dry_run=False):
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"""Execute updates on machines"""
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# Run nixos-rebuild switch
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# Monitor progress
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# Handle failures
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def verify(self, group=None):
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"""Verify updates completed successfully"""
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# Check system health
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# Verify services
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# Compare generations
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```
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## Monitoring and Alerting
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### Health Checks
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- Service availability checks
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- Resource usage monitoring
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- System log analysis
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- Network connectivity tests
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### Alerting Triggers
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- Update failures
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- Health check failures
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- Rollback events
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- Long-running updates
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### Notification Channels
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- Email notifications
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- Discord/Slack integration
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- Dashboard updates
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- Log aggregation
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## Safety Mechanisms
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### Pre-Update Validation
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- Configuration syntax checking
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- Dependency verification
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- Resource availability checks
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- Backup verification
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### During Update
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- Progress monitoring
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- Timeout handling
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- Partial failure recovery
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- Emergency stop capability
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### Post-Update
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- Service verification
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- Performance monitoring
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- Automatic rollback triggers
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- Success confirmation
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## Rollback Strategy
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### Automatic Rollback Triggers
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- Health check failures
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- Service startup failures
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- Critical error detection
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- Timeout exceeded
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### Manual Rollback
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```bash
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# Quick rollback to previous generation
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lab update rollback --group=critical --immediate
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# Rollback to specific generation
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lab update rollback --group=infrastructure --to-generation=150
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# Selective rollback (specific machines)
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lab update rollback --machine=db-primary,web-01
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```
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## Testing Strategy
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### Development Environment
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- Test updates in isolated environment
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- Validate scripts and configurations
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- Performance testing
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- Failure scenario testing
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### Staging Rollout
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- Deploy to staging group first
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- Automated testing suite
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- Manual verification
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- Production deployment
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## Security Considerations
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- Secure communication channels
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- Authentication for update commands
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- Audit logging
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- Access control for update scripts
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- Encrypted configuration storage
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## Future Enhancements
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### Advanced Scheduling
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- Maintenance window management
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- Business hour awareness
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- Holiday scheduling
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- Emergency update capabilities
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### Intelligence Features
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- Machine learning for optimal timing
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- Predictive failure detection
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- Automatic dependency discovery
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- Performance impact analysis
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### Integration Expansions
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- CI/CD pipeline integration
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- Cloud provider APIs
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- Container orchestration
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- Configuration management systems
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## Implementation Roadmap
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### Phase 1 (2 weeks)
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- Basic staggered update script
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- Simple group management
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- Nix integration
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- Basic health checks
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### Phase 2 (4 weeks)
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- Lab tool integration
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- Advanced scheduling
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- Monitoring and alerting
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- Rollback mechanisms
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### Phase 3 (6 weeks)
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- Advanced features
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- Performance optimization
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- Extended integrations
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- Documentation and training
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## Resources and References
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- NixOS Manual: System Administration
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- Cron Best Practices
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- Blue-Green Deployment Patterns
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- Infrastructure as Code Principles
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- Monitoring and Observability Patterns
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## Conclusion
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A well-designed staggered update system will significantly improve lab maintenance efficiency while reducing risk. The combination of Nix's atomic updates, careful orchestration, and comprehensive monitoring provides a robust foundation for automated infrastructure management.
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