Sensu Check Entropy

Description

This plugin provides native entropy instrumentation for monitoring and metrics collection of available system entropy on Linux systems.

The plugin includes:

• check-entropy: Monitor entropy levels with configurable warning and critical thresholds
• metrics-entropy: Collect entropy metrics in Graphite format for time-series databases

Both commands read the available entropy from /proc/sys/kernel/random/entropy_avail.

Installation

Binary Releases

Download the latest release from the releases page.

From Source

go install github.com/nmollerup/sensu-check-entropy/cmd/check-entropy@latest
go install github.com/nmollerup/sensu-check-entropy/cmd/metrics-entropy@latest

Configuration

Asset Registration

Assets are the recommended way to install plugins in Sensu. The asset can be configured using sensuctl:

sensuctl asset add nmollerup/sensu-check-entropy

Check Definition

Example check definition:

---
type: CheckConfig
api_version: core/v2
metadata:
  name: check-entropy
spec:
  command: check-entropy --warning 60 --critical 30
  subscriptions:
    - linux
  runtime_assets:
    - nmollerup/sensu-check-entropy
  interval: 60
  publish: true

Usage

check-entropy

Sensu check to monitor available system entropy

Usage:
  check-entropy [flags]

Flags:
  -c, --critical int        Critical threshold for available entropy (default 30)
  -h, --help                help for check-entropy
  -m, --metrics             Output entropy as metrics in Graphite format
  -s, --metric-scheme       Metric naming scheme when using --metrics (default: hostname.entropy)
  -w, --warning int         Warning threshold for available entropy (default 60)

Examples

Check with default thresholds (warning: 60, critical: 30):

check-entropy

Check with custom thresholds:

check-entropy --warning 100 --critical 50

Check using environment variables:

CHECK_ENTROPY_WARNING=100 CHECK_ENTROPY_CRITICAL=50 check-entropy

Output metrics in Graphite format:

check-entropy --metrics
# Output: hostname.entropy 256 1738147200

Output metrics with custom scheme:

check-entropy --metrics --metric-scheme myserver.system.entropy
# Output: myserver.system.entropy 256 1738147200

Output

The check will output one of the following states:

• OK: Entropy is above the warning threshold
• WARNING: Entropy is at or below the warning threshold but above the critical threshold
• CRITICAL: Entropy is at or below the critical threshold
• UNKNOWN: Unable to read entropy or invalid thresholds

Example outputs:

CheckEntropy OK: entropy is 256
CheckEntropy WARNING: entropy is 55
CheckEntropy CRITICAL: entropy is 25

metrics-entropy

Sensu metric plugin to collect system entropy metrics

Usage:
  metrics-entropy [flags]

Flags:
  -h, --help           help for metrics-entropy
  -s, --scheme string  Metric naming scheme, text to prepend to metric (default: hostname.entropy)

Examples

Collect entropy metrics with default scheme:

metrics-entropy
# Output: hostname.entropy 256 1738147200

Collect entropy metrics with custom scheme:

metrics-entropy --scheme production.server01.entropy
# Output: production.server01.entropy 256 1738147200

Example metric check definition:

---
type: CheckConfig
api_version: core/v2
metadata:
  name: metrics-entropy
spec:
  command: metrics-entropy
  subscriptions:
    - linux
  runtime_assets:
    - nmollerup/sensu-check-entropy
  interval: 60
  publish: true
  output_metric_format: graphite_plaintext
  output_metric_handlers:
    - influxdb

Platform Support

This plugin is designed for Linux systems only, as it reads from /proc/sys/kernel/random/entropy_avail.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

MIT License - see LICENSE file for details.