319 lines
8.3 KiB
Markdown
319 lines
8.3 KiB
Markdown
# SCRON
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A lightweight, efficient cron-like scheduler written in Go that executes shell commands at specified intervals with precise timing, comprehensive logging, and flexible notification support.
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## Features
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- **🕐 Flexible Scheduling**: Advanced cron-like time patterns with minute-level precision
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- **🔄 Dynamic Configuration**: Automatic config reloading without restart
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- **📊 Structured Logging**: JSON-formatted logs with zerolog for easy parsing
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- **🔔 Multi-Channel Notifications**: Support for Gotify and SMTP notifications
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- **⚡ Concurrent Execution**: Jobs run in parallel for optimal performance
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- **🛡️ Robust Error Handling**: Comprehensive error tracking with exit codes
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- **📝 Output Capture**: Combined stdout/stderr capture for debugging
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## Installation
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### From Source
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```bash
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# Clone the repository
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git clone https://github.com/yourusername/scron.git
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cd scron
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# Build the binary
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go build -o scron ./
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# Run
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./scron
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```
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### Debian Package
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Download the latest `.deb` package from the [releases page](https://git.keks.cloud/kekskurse/scron/releases):
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```bash
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# Install package
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sudo dpkg -i scron_X.X.X_linux_amd64.deb
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```
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Configuration file location: `/etc/scron/config.yml`
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## Configuration
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Create a `config.yml` file in the same directory as the binary (or `/etc/scron/` for package installations):
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### Basic Configuration
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```yaml
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jobs:
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- name: "System Health Check"
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minute: "*/5"
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hour: "*"
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command: "curl -f http://localhost:8080/health || exit 1"
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- name: "Daily Backup"
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minute: "0"
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hour: "2"
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command: "/usr/local/bin/backup.sh"
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```
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### Advanced Configuration with Notifications
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```yaml
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# Notification configurations
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notification:
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- name: default
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success:
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gotify:
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url: "https://gotify.example.com/message?token=YOUR_TOKEN"
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smtp:
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host: "smtp.gmail.com"
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port: 587
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username: "your-email@gmail.com"
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password: "your-app-password"
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from: "scron@example.com"
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to: "admin@example.com"
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use_ssl: true
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error:
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gotify:
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url: "https://gotify.example.com/message?token=YOUR_CRITICAL_TOKEN"
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smtp:
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host: "smtp.gmail.com"
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port: 587
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username: "your-email@gmail.com"
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password: "your-app-password"
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from: "scron-alerts@example.com"
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to: "oncall@example.com"
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use_ssl: true
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- name: critical-only
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error:
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gotify:
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url: "https://gotify.example.com/message?token=YOUR_CRITICAL_TOKEN"
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# Job definitions
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jobs:
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- name: "Database Backup"
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minute: "0"
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hour: "3"
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command: "pg_dump mydb > /backup/mydb_$(date +%Y%m%d).sql"
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notification: default
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- name: "Critical Service Monitor"
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minute: "*/1"
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hour: "*"
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command: "systemctl is-active nginx || exit 1"
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notification: critical-only
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```
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## Time Pattern Syntax
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SCRON supports flexible cron-like time patterns for both minutes (0-59) and hours (0-23):
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| Pattern | Description | Example |
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|---------|-------------|---------|
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| `*` | Every minute/hour | `minute: "*"` - every minute |
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| `n` | Specific value | `hour: "14"` - at 2 PM |
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| `*/n` | Every n intervals | `minute: "*/15"` - every 15 minutes |
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| `n,m` | Multiple values | `hour: "9,12,17"` - at 9 AM, noon, and 5 PM |
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| `n-m` | Range (inclusive) | `hour: "9-17"` - 9 AM to 5 PM |
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| `n-m/s` | Range with step | `minute: "10-50/10"` - at 10, 20, 30, 40, 50 |
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| `n-m,x-y` | Multiple ranges | `hour: "0-6,20-23"` - night hours |
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### Pattern Examples
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```yaml
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jobs:
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# Every minute
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- name: "Heartbeat"
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minute: "*"
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hour: "*"
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command: "echo 'alive'"
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# Every 5 minutes
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- name: "Frequent Check"
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minute: "*/5"
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hour: "*"
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command: "check-service.sh"
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# At specific minutes
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- name: "Quarter Hours"
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minute: "0,15,30,45"
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hour: "*"
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command: "quarter-hour-task.sh"
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# Business hours only (9 AM - 5 PM)
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- name: "Business Task"
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minute: "0"
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hour: "9-17"
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command: "business-process.sh"
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# Complex schedule
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- name: "Complex Task"
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minute: "5-55/10" # At 5, 15, 25, 35, 45, 55
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hour: "8-18/2" # Every 2 hours from 8 AM to 6 PM
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command: "complex-task.sh"
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```
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## Notification Configuration
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### Gotify Configuration
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```yaml
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notification:
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- name: gotify-alerts
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success:
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gotify:
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url: "https://gotify.example.com/message?token=YOUR_TOKEN"
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error:
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gotify:
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url: "https://gotify.example.com/message?token=YOUR_PRIORITY_TOKEN"
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```
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Gotify notifications include:
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- ✅ Success messages with low priority (-1)
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- ❌ Error messages with high priority (10)
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- Job name, command, and output in the message body
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### SMTP Configuration
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```yaml
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notification:
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- name: email-alerts
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success:
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smtp:
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host: "smtp.office365.com"
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port: 587
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username: "notifications@company.com"
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password: "secure-password"
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from: "scron@company.com"
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to: "devops@company.com"
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use_ssl: true
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error:
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smtp:
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host: "smtp.office365.com"
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port: 587
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username: "alerts@company.com"
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password: "secure-password"
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from: "scron-alerts@company.com"
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to: "oncall@company.com"
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use_ssl: true
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```
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### Multiple Notification Channels
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You can configure both Gotify and SMTP in the same notification configuration - both will be used:
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```yaml
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notification:
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- name: multi-channel
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error:
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gotify:
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url: "https://gotify.example.com/message?token=TOKEN"
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smtp:
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host: "smtp.gmail.com"
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port: 587
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username: "alerts@example.com"
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password: "app-password"
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from: "scron@example.com"
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to: "team@example.com"
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use_ssl: true
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```
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## Advanced Examples
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### Database Maintenance
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```yaml
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jobs:
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- name: "PostgreSQL Vacuum"
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minute: "0"
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hour: "4"
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command: "psql -U postgres -d mydb -c 'VACUUM ANALYZE;'"
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notification: database-alerts
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- name: "MySQL Backup"
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minute: "30"
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hour: "3"
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command: |
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mysqldump --all-databases > /backup/mysql_$(date +%Y%m%d_%H%M%S).sql && \
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find /backup -name "mysql_*.sql" -mtime +7 -delete
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notification: backup-alerts
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```
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### System Monitoring
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```yaml
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jobs:
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- name: "Disk Space Check"
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minute: "*/30"
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hour: "*"
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command: |
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USAGE=$(df -h / | awk 'NR==2 {print $5}' | sed 's/%//')
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if [ $USAGE -gt 80 ]; then
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echo "WARNING: Disk usage is at ${USAGE}%"
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exit 1
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fi
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notification: critical-alerts
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- name: "Memory Check"
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minute: "*/10"
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hour: "*"
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command: |
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FREE_MEM=$(free -m | awk 'NR==2 {print $4}')
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if [ $FREE_MEM -lt 500 ]; then
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echo "Low memory: ${FREE_MEM}MB free"
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exit 1
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fi
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notification: system-alerts
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```
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### Log Rotation
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```yaml
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jobs:
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- name: "Rotate Application Logs"
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minute: "0"
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hour: "0"
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command: |
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find /var/log/myapp -name "*.log" -size +100M -exec gzip {} \; && \
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find /var/log/myapp -name "*.gz" -mtime +30 -delete
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```
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## Logging
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SCRON uses structured JSON logging with zerolog. Logs include:
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- Job execution start/completion
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- Command output (stdout and stderr)
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- Exit codes
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- Execution errors
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- Configuration reload events
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- Notification delivery status
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Example log output:
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```json
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{"level":"info","time":"2024-01-15T10:00:00Z","message":"Executing job","job":"Database Backup","command":"pg_dump mydb > backup.sql"}
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{"level":"info","time":"2024-01-15T10:00:05Z","message":"Job completed","job":"Database Backup","exit_code":0}
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```
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## Error Handling
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SCRON provides comprehensive error handling:
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- **Configuration Errors**: Invalid YAML, missing required fields
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- **Time Pattern Errors**: Invalid cron patterns with detailed error messages
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- **Execution Errors**: Command failures, non-zero exit codes
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- **Notification Errors**: Failed delivery attempts are logged but don't stop job execution
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## Best Practices
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1. **Use Absolute Paths**: Always use absolute paths in commands to avoid PATH issues
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2. **Set Proper Exit Codes**: Ensure your scripts exit with non-zero codes on failure
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3. **Test Commands**: Test your commands manually before adding to configuration
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4. **Monitor Logs**: Regularly check SCRON logs for execution issues
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5. **Use Notifications Wisely**: Configure different notification channels for different severity levels
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6. **Keep Commands Simple**: For complex tasks, use shell scripts instead of inline commands
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