# Nagios Plugin Integration Guide

The Heartbeat monitoring system now supports running existing Nagios-compatible monitoring plugins through the `nagios_runner` plugin. This allows you to leverage the thousands of existing Nagios plugins without modification.

## Quick Start

### 1. Install Nagios Plugins

**Debian/Ubuntu:**
```bash
sudo apt-get install nagios-plugins
```

**RHEL/CentOS/Fedora:**
```bash
sudo yum install nagios-plugins-all
# or
sudo dnf install nagios-plugins-all
```

**Arch Linux:**
```bash
sudo pacman -S monitoring-plugins
```

### 2. Configure Heartbeat

Add the `nagios_runner` section to your `~/.hb.yaml` config:

```yaml
nagios_runner:
  interval: 60          # Run plugins every 60 seconds
  timeout: 30           # Command timeout in seconds
  commands:
    - name: check_disk_root
      command: /usr/lib/nagios/plugins/check_disk -w 20% -c 10% -p /
    
    - name: check_load
      command: /usr/lib/nagios/plugins/check_load -w 5,4,3 -c 10,8,6
    
    - name: check_procs
      command: /usr/lib/nagios/plugins/check_procs -w 250 -c 400
```

### 3. Start Heartbeat Client

```bash
hbc -v localhost
```

The client will now execute the configured Nagios plugins and send their results to the server.

## How It Works

### Nagios Plugin Standard

Nagios plugins follow a simple interface:

1. **Exit Codes:**
   - `0` = OK
   - `1` = WARNING
   - `2` = CRITICAL
   - `3` = UNKNOWN

2. **Output Format:**
   ```
   STATUS - Message | performance_data
   ```

3. **Performance Data Format:**
   ```
   'label'=value[UOM];[warn];[crit];[min];[max]
   ```

### Example Plugin Output

```bash
$ /usr/lib/nagios/plugins/check_disk -w 20% -c 10% -p /
DISK OK - free space: / 156 GB (78%); | /=44GB;127;142;0;159
```

This output includes:
- **Status:** `DISK OK`
- **Message:** `free space: / 156 GB (78%)`
- **Performance Data:** `/=44GB;127;142;0;159`
  - Current value: 44GB
  - Warning threshold: 127GB
  - Critical threshold: 142GB
  - Min: 0GB
  - Max: 159GB

### Data Collected

The `nagios_runner` plugin collects:

**For each configured command:**
- `{name}_status` - Status string (OK, WARNING, CRITICAL, UNKNOWN)
- `{name}_status_code` - Numeric exit code (0-3)
- `{name}_output` - Status message
- `{name}_{metric}` - Each performance metric value
- `{name}_{metric}_uom` - Unit of measurement (if present)
- `{name}_{metric}_warn` - Warning threshold (if present)
- `{name}_{metric}_crit` - Critical threshold (if present)
- `{name}_{metric}_min` - Minimum value (if present)
- `{name}_{metric}_max` - Maximum value (if present)

## Configuration Options

```yaml
nagios_runner:
  # Collection interval in seconds (default: 60)
  interval: 60
  
  # Command execution timeout in seconds (default: 30)
  timeout: 30
  
  # Execute commands via shell (default: true)
  # Set to false for direct execution (more secure but less flexible)
  shell: true
  
  # List of Nagios plugins to run
  commands:
    - name: unique_name       # Required: unique identifier
      command: /path/to/plugin [args]  # Required: full command to execute
```

## Common Nagios Plugins

### System Resources

**Disk Space:**
```yaml
- name: check_disk_root
  command: /usr/lib/nagios/plugins/check_disk -w 20% -c 10% -p /
```

**Load Average:**
```yaml
- name: check_load
  command: /usr/lib/nagios/plugins/check_load -w 5,4,3 -c 10,8,6
```

**Swap Usage:**
```yaml
- name: check_swap
  command: /usr/lib/nagios/plugins/check_swap -w 20% -c 10%
```

**Process Count:**
```yaml
- name: check_procs
  command: /usr/lib/nagios/plugins/check_procs -w 250 -c 400
```

**Users Logged In:**
```yaml
- name: check_users
  command: /usr/lib/nagios/plugins/check_users -w 5 -c 10
```

### Network Services

**SSH:**
```yaml
- name: check_ssh
  command: /usr/lib/nagios/plugins/check_ssh localhost
```

**HTTP:**
```yaml
- name: check_http_local
  command: /usr/lib/nagios/plugins/check_http -H localhost
  
- name: check_http_ssl
  command: /usr/lib/nagios/plugins/check_http -H example.com --ssl
```

**DNS:**
```yaml
- name: check_dns
  command: /usr/lib/nagios/plugins/check_dns -H google.com
```

**Ping:**
```yaml
- name: check_ping_gateway
  command: /usr/lib/nagios/plugins/check_ping -H 192.168.1.1 -w 100,20% -c 500,60%
```

### Databases

**MySQL:**
```yaml
- name: check_mysql
  command: /usr/lib/nagios/plugins/check_mysql -H localhost -u user -p password
```

**PostgreSQL:**
```yaml
- name: check_pgsql
  command: /usr/lib/nagios/plugins/check_pgsql -H localhost -d database
```

## Writing Custom Nagios Plugins

You can write your own Nagios-compatible plugins in any language. Here's a simple example:

**Bash:**
```bash
#!/bin/bash
# /usr/local/bin/check_example.sh

# Get the value to check
value=$(some_command)

# Define thresholds
warn=80
crit=90

# Check and output result
if [ $value -ge $crit ]; then
    echo "CRITICAL - Value is $value | value=${value};${warn};${crit};0;100"
    exit 2
elif [ $value -ge $warn ]; then
    echo "WARNING - Value is $value | value=${value};${warn};${crit};0;100"
    exit 1
else
    echo "OK - Value is $value | value=${value};${warn};${crit};0;100"
    exit 0
fi
```

**Python:**
```python
#!/usr/bin/env python3
# /usr/local/bin/check_example.py

import sys

def check_something():
    value = get_value()  # Your check logic here
    warn = 80
    crit = 90
    
    perfdata = f"value={value};{warn};{crit};0;100"
    
    if value >= crit:
        print(f"CRITICAL - Value is {value} | {perfdata}")
        sys.exit(2)
    elif value >= warn:
        print(f"WARNING - Value is {value} | {perfdata}")
        sys.exit(1)
    else:
        print(f"OK - Value is {value} | {perfdata}")
        sys.exit(0)

if __name__ == "__main__":
    check_something()
```

Then configure in Heartbeat:
```yaml
nagios_runner:
  commands:
    - name: my_custom_check
      command: /usr/local/bin/check_example.sh
```

## Troubleshooting

### Plugin not found
```
Error: Command not found
```
**Solution:** Use the full path to the plugin. Common locations:
- `/usr/lib/nagios/plugins/`
- `/usr/lib64/nagios/plugins/`
- `/usr/local/nagios/libexec/`

### Permission denied
```
Error: Permission denied
```
**Solution:** Ensure the plugin is executable:
```bash
chmod +x /path/to/plugin
```

### Timeout errors
```
Command timed out after 30s
```
**Solution:** Increase the timeout in config:
```yaml
nagios_runner:
  timeout: 60  # Increase timeout
```

### No performance data
If performance data is not being parsed:
1. Check plugin output includes `|` separator
2. Verify performance data format: `'label'=value[UOM];...`
3. Enable debug logging: `hbc -v -x localhost`

## Benefits

1. **Massive Plugin Library:** Thousands of existing Nagios plugins available
2. **No Rewriting:** Use plugins as-is without modification
3. **Community Support:** Well-documented and maintained plugins
4. **Flexibility:** Mix Nagios plugins with native Heartbeat plugins
5. **Standard Interface:** Consistent exit codes and output format
6. **Performance Data:** Automatic extraction of metrics

## Resources

- [Nagios Plugin Development Guidelines](https://nagios-plugins.org/doc/guidelines.html)
- [Monitoring Plugins Project](https://www.monitoring-plugins.org/)
- [Nagios Exchange](https://exchange.nagios.org/) - Plugin repository
- [Check_MK Local Checks](https://docs.checkmk.com/latest/en/localchecks.html) - Compatible format

## Next Steps

- Configure threshold alerts based on Nagios plugin status codes
- View plugin data in the Heartbeat web UI
- Create custom plugins for your specific monitoring needs
- Integrate with existing Nagios/Icinga configurations