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Health Checks

The BookWorm application implements comprehensive health monitoring using ASP.NET Core health checks, providing real-time insights into service availability and dependencies.

Health Check Architecture​

Core Components​

  • AspNetCore.HealthChecks.UI.Client - Health check UI and reporting
  • AspNetCore.HealthChecks.Uris - HTTP endpoint health monitoring
  • Grpc.AspNetCore.HealthChecks - gRPC service health checks
  • Custom Health Checks - Application-specific health monitoring

Health Check Types​

  • Readiness Checks - Service is ready to accept traffic
  • Liveness Checks - Service is running and responsive
  • Startup Checks - Service has completed initialization
  • Dependency Checks - External service and resource availability

Standard Health Endpoints​

Health Check Endpoints​

  • /health - Comprehensive health status with detailed information
  • /alive - Simple liveness check for container orchestrators
  • Custom Endpoints - Service-specific health monitoring endpoints

Response Formats​

  • JSON Format - Structured health status information
  • Status Codes - HTTP status codes indicating health state
  • Detailed Responses - Component-level health information
  • Metrics Integration - Health metrics for monitoring systems

Dependency Health Checks​

Database Health​

  • PostgreSQL Connectivity - Database connection and query execution
  • Connection Pool Status - Available connections and performance metrics
  • Migration Status - Database schema version and integrity
  • Query Performance - Response time and timeout monitoring

Message Bus Health​

  • RabbitMQ Connectivity - Message broker connection status
  • Queue Status - Queue depth and processing rates
  • Publisher Confirmation - Message delivery confirmation
  • Consumer Health - Message processing capability

External Service Health​

  • HTTP Dependency Checks - External API availability and response times
  • gRPC Service Checks - Remote service connectivity and health
  • Authentication Provider - Keycloak identity service availability
  • Cache Service Health - Redis or other caching service status

Health Check Configuration​

Service Registration​

  • Automatic Registration - Health checks registered through service defaults
  • Conditional Registration - Environment-specific health checks
  • Dependency Injection - Health check services and dependencies
  • Configuration Binding - Health check settings from configuration

Check Intervals​

  • Periodic Execution - Scheduled health check execution
  • Configurable Intervals - Different intervals for different check types
  • Timeout Configuration - Health check timeout settings
  • Retry Logic - Failed check retry mechanisms

Monitoring Integration​

Health Check UI​

  • Visual Dashboard - Web-based health monitoring interface
  • Historical Data - Health status trends and history
  • Alert Configuration - Notification settings for health failures
  • Multi-Service View - Centralized monitoring for all services

Metrics and Telemetry​

  • Health Metrics - Prometheus-compatible health metrics
  • OpenTelemetry Integration - Health status in distributed tracing
  • Custom Metrics - Application-specific health indicators
  • Performance Counters - System resource monitoring

Container Orchestration​

Kubernetes Integration​

  • Readiness Probes - Service readiness for traffic routing
  • Liveness Probes - Container restart triggers
  • Startup Probes - Initialization completion detection
  • Custom Probes - Application-specific health checks

Docker Health Checks​

  • HEALTHCHECK Instruction - Container-level health monitoring
  • Health Status Propagation - Container orchestrator integration
  • Graceful Shutdown - Health-aware service termination
  • Rolling Updates - Health-based deployment strategies

Best Practices​

Health Check Design​

  • Fast Execution - Health checks should complete quickly
  • Dependency Testing - Check critical dependencies without causing load
  • Graceful Degradation - Partial functionality when dependencies are unavailable
  • Clear Status Messages - Descriptive health status information

Performance Considerations​

  • Lightweight Checks - Minimal resource usage for health monitoring
  • Caching Results - Cache health check results to reduce overhead
  • Circuit Breaker Integration - Respect circuit breaker states
  • Load Balancer Integration - Health status for traffic routing decisions

Operational Guidelines​

  • Alert Thresholds - Appropriate alerting for different health states
  • Escalation Procedures - Define response procedures for health failures
  • Documentation - Document health check meanings and troubleshooting
  • Testing - Regular testing of health check accuracy and reliability