CheckMate

CheckMate is a service monitoring tool written in Go that provides real-time health checks and metrics for infrastructure. It supports multiple protocols, customizable rules, and Prometheus integration.

DISCLAIMER: This is a personal project and is not meant to be used in a production environment as it is not feature complete nor secure nor tested and under heavy development.

Features

Core Features

• Multi-protocol support (TCP, HTTP, HTTPS with cert validation, SMTP, DNS)
• Hierarchical configuration (Sites → Groups → Hosts → Checks)
• High availability monitoring with configurable modes
• Configurable check intervals per service
• Prometheus metrics integration
• Simple Rule-based monitoring with custom conditions
• Flexible notification system
• Service tagging system
• TLS certificate expiration monitoring

High Availability Monitoring

Groups support two monitoring modes that can be configured at different levels:

• All Mode (Default)

  • Group is considered "up" if any host is responding
  • Rules only trigger when all hosts are down
  • For redundant services where one available host is sufficient

• Any Mode

  • Group monitoring tracks all hosts individually
  • Rules trigger when any host goes down
  • Suitable for services where each host's availability is critical

Rule modes can be configured at three levels (in order of precedence):

1. Check level - Overrides group settings for specific checks
2. Group level - Default for all checks in the group
3. Default - Falls back to "all" mode if not specified

Configuration

Site Configuration

• monitorSite: Name of the monitoring instance
• sites: List of infrastructure sites to monitor
  • name: Site identifier
  • tags: Site-level tags
  • groups: List of service groups

Group Configuration

• name: Group identifier
• tags: Group-level tags (combined with site tags)
• hosts: List of hosts to monitor
  • host: Hostname or IP
  • tags: Host-specific tags
• checks: Service checks applied to all hosts
  • port: Port number
  • protocol: TCP, HTTP, SMTP, or DNS
  • interval: Check frequency (e.g., "30s", "1m")
  • tags: Check-specific tags
  • ruleMode: Override group's rule mode
  • verifyCert: Enable certificate checking
• ruleMode: Group-level rule mode ("all" or "any")

Rule Configuration

• name: Rule identifier
• condition: Expression using downtime and responseTime variables
• tags: Tags to match against groups
• notifications: Notification types to use

Notification Configuration

• type: Notification type ("log", more coming soon)

Certificate Rule Configuration

• name: Rule identifier
• minDaysValidity: Number of days before expiration to trigger alert
• tags: Tags to match against groups/checks
• notifications: Notification types to use

Metrics

Prometheus Integration

• Node metrics for hosts and groups
• Edge metrics for relationships
• Response time histograms
• Success/failure counters
• Host availability tracking

All metrics are exposed on :9100/metrics with the checkmate_ prefix.

Metrics

CheckMate exposes Prometheus metrics at :9100/metrics:

Core Metrics

• checkmate_check_success: Service availability (1 = up, 0 = down)
• checkmate_check_latency_milliseconds: Response time in milliseconds
• checkmate_check_latency_milliseconds_histogram: Response time distribution
• checkmate_hosts_up: Number of hosts up in a group (per port/protocol)
• checkmate_hosts_total: Total number of hosts in a group (per port/protocol)
• checkmate_cert_expiry_days: Days until certificate expiration

Graph Visualization Metrics (In Development)

Note: These metrics are designed for Grafana's Node Graph visualization and are currently in flux

• checkmate_node_info: Node information for graph visualization

  • Labels: id, type (site/group/host), name, tags, port, protocol
  • Values: 1 for active nodes, 0 for inactive

• checkmate_edge_info: Edge information with latency

  • Labels: source, target, type, metric, port, protocol
  • Values: latency in milliseconds

Example Prometheus queries:

# Filter checks by site
checkmate_check_success{site="mars-lab"}

# Average response time for production APIs
avg(checkmate_check_latency_milliseconds{tags=~".*prod.*", tags=~".*api.*"})

# 95th percentile latency by site
histogram_quantile(0.95, sum(rate(checkmate_check_latency_milliseconds_histogram[5m])) by (le, site))

# Host availability ratio per group
sum(checkmate_hosts_up) by (id) / sum(checkmate_hosts_total) by (id)

# Graph Visualization (In Development)
checkmate_node_info{type="host", port="443", protocol="HTTPS"}
avg(checkmate_edge_info{type="contains", metric="latency"}) by (source, target, port, protocol)

Grafana Node Graph Setup (In Development)

To visualize your infrastructure in Grafana's Node Graph:

1. Create a new Node Graph panel
2. Configure the Node Query:

   checkmate_node_info
   

3. Configure the Edge Query:

   checkmate_edge_info{metric="latency"}
   

4. Set transformations:
   • Nodes: Use 'id' for node ID, 'type' for node class
   • Edges: Use 'source' and 'target' for connections

Note: Graph visualization features are in flux and the query/configuration interface may change

Health Checks

CheckMate provides Kubernetes-compatible health check endpoints:

• /health/live - Liveness probe

  • Returns 200 OK when the service is running

• /health/ready - Readiness probe

  • Returns 200 OK when ready to receive traffic
  • Returns 503 Service Unavailable during initialization

All health check endpoints are served on port 9100 alongside metrics.

Roadmap

• Notification system expansion (Slack, Email)
• Configurable notification thresholds
• Database support for historical data
• Docker container
• Web UI for monitoring (MAYBE)
• Additional protocol support (HTTPS, TLS verification)
• Kubernetes readiness/liveness probe support
• Multiple host monitoring
• Multi-protocol per host
• Service tagging system
• Site-based infrastructure organization
• High availability group monitoring

License

This project is licensed under the GNU General Public License v3.0 - see the LICENSE file for details.

Development

Prerequisites

• Go 1.21 or higher
• air for live reloading (optional)

Live Reloading

For development with automatic rebuilding on code changes:

1. Install Air:

go install github.com/air-verse/air@latest

2. Run with Air:

air