Health Checks

Health check endpoints, response format, component checks, and load balancer / container integration.

Available Endpoints ​

Basic Health Check ​

GET /health
Authorization: Bearer {token}

Returns basic health status:

{
  "status": "Healthy",
  "timestamp": "2024-01-20T10:30:00Z",
  "cache_expires_in": "15 seconds"
}

Status Values:

• Healthy - All checks passing
• Degraded - Some issues detected
• Unhealthy - Critical issues found

Liveness Check ​

GET /health/live

Simple endpoint for container orchestration:

Alive

Features:

• No authentication required
• Minimal overhead
• 5-second cache
• Used by load balancers and Kubernetes

Detailed Health Check ​

GET /health/details
Authorization: Bearer {token}

Comprehensive health information:

{
  "status": "Healthy",
  "timestamp": "2024-01-20T10:30:00Z",
  "cache_expires_in": "60 seconds",
  "checks": [
    {
      "name": "Database",
      "status": "Healthy",
      "description": "Database connection successful",
      "duration": "45.23ms",
      "data": {
        "connectionString": "Configured",
        "responseTime": "12ms"
      },
      "tags": ["database", "sql"]
    },
    {
      "name": "Diskspace",
      "status": "Healthy",
      "description": "Disk space: 65% remaining",
      "duration": "2.15ms",
      "data": {
        "percentFree": "65%"
      },
      "tags": ["storage", "system"]
    },
    {
      "name": "ProxyEndpoints",
      "status": "Healthy",
      "description": "All proxy services are responding",
      "duration": "234.56ms",
      "data": {
        "Account": {
          "Status": "Healthy",
          "StatusCode": 200,
          "ReasonPhrase": "OK"
        },
        "Products": {
          "Status": "Healthy",
          "StatusCode": 401,
          "ReasonPhrase": "Unauthorized - Marked as Healthy"
        }
      },
      "tags": ["proxies", "external", "readiness"]
    }
  ],
  "totalDuration": "282.94ms",
  "version": "1.0.0"
}

Health Check Components ​

Database Check ​

Verifies SQL database connectivity:

{
  "name": "Database",
  "status": "Healthy",
  "description": "Database connection successful",
  "duration": "45.23ms",
  "data": {
    "connectionString": "Configured",
    "responseTime": "12ms"
  }
}

Checks:

• Connection availability
• Response time
• Authentication status

Disk Space Check ​

Monitors available storage:

{
  "name": "Diskspace",
  "status": "Degraded",
  "description": "Low disk space: 15% remaining",
  "duration": "2.15ms",
  "data": {
    "percentFree": "15%"
  }
}

Thresholds:

• Healthy: > 15% free
• Degraded: 5-15% free
• Unhealthy: < 5% free

Proxy Endpoints Check ​

Tests external service connectivity:

{
  "name": "ProxyEndpoints",
  "status": "Healthy",
  "description": "All proxy services are responding",
  "duration": "234.56ms",
  "data": {
    "Account": {
      "Status": "Healthy",
      "StatusCode": 200
    },
    "Products": {
      "Status": "Unhealthy",
      "Error": "Connection timeout"
    }
  }
}

Features:

• Random endpoint sampling
• Timeout handling (5 seconds)
• Authentication status checking

Configuration ​

appsettings.json ​

{
  "HealthChecks": {
    "Enabled": true,
    "CacheTimeSeconds": 30,
    "ProxyTimeout": 5000,
    "DiskSpaceWarningThreshold": 15,
    "DiskSpaceCriticalThreshold": 5
  }
}

Environment Variables ​

# Override cache duration
HEALTHCHECK_CACHE_TIME=60

# Disable proxy checks
HEALTHCHECK_SKIP_PROXY=true

# Custom disk thresholds
HEALTHCHECK_DISK_WARNING=20
HEALTHCHECK_DISK_CRITICAL=10

Implementation Details ​

Caching Strategy ​

Health checks use intelligent caching to prevent overload:

Response Headers ​

Cache-Control: public, max-age=15
Expires: Sun, 20 Jan 2024 10:30:15 GMT

Error Handling ​

Health checks handle failures gracefully:

1. Database Errors

   json

   {
     "name": "Database",
     "status": "Unhealthy",
     "description": "Connection failed: Timeout",
     "duration": "5000ms",
     "data": {
       "error": "SqlException: Connection timeout"
     }
   }

2. Proxy Failures

   json

   {
     "name": "ProxyEndpoints",
     "status": "Degraded",
     "description": "Some services unavailable",
     "data": {
       "Account": {
         "Status": "Healthy"
       },
       "Products": {
         "Status": "Unhealthy",
         "Error": "HTTP 503 Service Unavailable"
       }
     }
   }

Load Balancer Configuration ​

IIS ARR ​

<configuration>
  <system.webServer>
    <rewrite>
      <rules>
        <rule name="Health Check">
          <match url="^health/live$" />
          <action type="Rewrite" url="http://backend/health/live" />
        </rule>
      </rules>
    </rewrite>
    <applicationRequestRouting>
      <health checkUrl="http://backend/health/live" />
    </applicationRequestRouting>
  </system.webServer>
</configuration>

NGINX ​

upstream portway_api {
    server backend1:5000;
    server backend2:5000;
    
    # Health check configuration
    health_check uri=/health/live interval=5s;
}

server {
    location /health/live {
        proxy_pass http://portway_api;
        proxy_cache off;
    }
}

HAProxy ​

backend portway_api
    option httpchk GET /health/live
    http-check expect status 200
    
    server api1 10.0.1.10:5000 check inter 5s
    server api2 10.0.1.11:5000 check inter 5s

Kubernetes Integration ​

Liveness Probe ​

apiVersion: apps/v1
kind: Deployment
metadata:
  name: portway-api
spec:
  template:
    spec:
      containers:
      - name: portway
        livenessProbe:
          httpGet:
            path: /health/live
            port: 5000
          initialDelaySeconds: 10
          periodSeconds: 10
          timeoutSeconds: 5

Readiness Probe ​

readinessProbe:
  httpGet:
    path: /health
    port: 5000
    httpHeaders:
    - name: Authorization
      value: Bearer ${HEALTH_CHECK_TOKEN}
  initialDelaySeconds: 15
  periodSeconds: 20
  timeoutSeconds: 10

Startup Probe ​

startupProbe:
  httpGet:
    path: /health/live
    port: 5000
  failureThreshold: 30
  periodSeconds: 10

Troubleshooting ​

Common Issues ​

1. Health Check Timeouts

   txt

   Symptom: Health checks timing out
   Cause: Slow database or proxy responses
   Solution: Increase timeout values or investigate performance

2. Cache Issues

   txt

   Symptom: Stale health data
   Cause: Cache not expiring properly
   Solution: Check cache headers and configuration

3. Authentication Failures

   txt

   Symptom: 401 Unauthorized on /health
   Cause: Missing or invalid token
   Solution: Provide valid authentication token

Diagnostic Commands ​

# Test basic health
Invoke-WebRequest -Uri "http://localhost:5000/health" `
  -Headers @{"Authorization"="Bearer $token"}

# Check liveness
Invoke-WebRequest -Uri "http://localhost:5000/health/live"

# Get detailed status
$response = Invoke-WebRequest -Uri "http://localhost:5000/health/details" `
  -Headers @{"Authorization"="Bearer $token"}
$response.Content | ConvertFrom-Json | Format-List

Log Analysis ​

[10:30:00 INF] Health check cache refreshed. Status: Healthy
[10:30:01 WRN] Health check failed: Low disk space: 10% remaining
[10:30:02 ERR] Proxy endpoint 'Products' failed: Connection timeout