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Health Check Utility

Health check utility for monitoring service connectivity to Stellio, Neo4j, Fuseki, PostgreSQL, and external APIs.

Overview​

graph TB
    subgraph HealthCheck
        CHECK[Health Checker]
        AGGREGATE[Aggregator]
    end
    
    subgraph Services
        STELLIO[Stellio]
        NEO4J[Neo4j]
        FUSEKI[Fuseki]
        POSTGRES[PostgreSQL]
    end
    
    subgraph External
        GEMINI[Gemini API]
        TAVILY[Tavily API]
    end
    
    CHECK --> STELLIO
    CHECK --> NEO4J
    CHECK --> FUSEKI
    CHECK --> POSTGRES
    CHECK --> GEMINI
    CHECK --> TAVILY
    
    STELLIO --> AGGREGATE
    NEO4J --> AGGREGATE
    FUSEKI --> AGGREGATE
    POSTGRES --> AGGREGATE
    GEMINI --> AGGREGATE
    TAVILY --> AGGREGATE

Features​

FeatureDescription
Liveness ProbeIs the server running?
Readiness ProbeIs the server ready for requests?
Dependency CheckIndividual service status
Timeout Handling5s timeout per check
Aggregate StatusOverall health determination

API Endpoint​

GET /api/health​

Returns overall health status and individual service statuses.

Response (Healthy):

{
  "status": "healthy",
  "timestamp": "2025-11-29T10:30:00.000Z",
  "uptime": 3600,
  "services": {
    "stellio": {
      "status": "connected",
      "latency": 45,
      "version": "1.5.0"
    },
    "neo4j": {
      "status": "connected",
      "latency": 28
    },
    "fuseki": {
      "status": "connected",
      "latency": 35
    },
    "postgres": {
      "status": "connected",
      "latency": 12
    }
  }
}

Response (Degraded):

{
  "status": "degraded",
  "timestamp": "2025-11-29T10:30:00.000Z",
  "uptime": 3600,
  "services": {
    "stellio": {
      "status": "connected",
      "latency": 45
    },
    "neo4j": {
      "status": "error",
      "error": "Connection refused",
      "lastSuccess": "2025-11-29T10:25:00.000Z"
    },
    "fuseki": {
      "status": "connected",
      "latency": 35
    },
    "postgres": {
      "status": "connected",
      "latency": 12
    }
  }
}

Implementation​

// utils/healthCheck.ts
export interface ServiceHealth {
  status: 'connected' | 'error' | 'timeout';
  latency?: number;
  error?: string;
  version?: string;
  lastSuccess?: string;
}

export interface HealthCheckResult {
  status: 'healthy' | 'degraded' | 'unhealthy';
  timestamp: string;
  uptime: number;
  services: Record<string, ServiceHealth>;
}

export async function performHealthCheck(): Promise<HealthCheckResult> {
  const startTime = Date.now();
  
  const [stellio, neo4j, fuseki, postgres] = await Promise.all([
    checkStellioHealth(),
    checkNeo4jHealth(),
    checkFusekiHealth(),
    checkPostgresHealth()
  ]);
  
  const services = { stellio, neo4j, fuseki, postgres };
  const status = determineOverallStatus(services);
  
  return {
    status,
    timestamp: new Date().toISOString(),
    uptime: process.uptime(),
    services
  };
}

Individual Health Checks​

Stellio Health Check​

async function checkStellioHealth(): Promise<ServiceHealth> {
  const start = Date.now();
  try {
    const response = await axios.get(`${STELLIO_URL}/health`, {
      timeout: 5000
    });
    return {
      status: 'connected',
      latency: Date.now() - start,
      version: response.data.version
    };
  } catch (error) {
    return {
      status: 'error',
      error: error.message
    };
  }
}

Neo4j Health Check​

async function checkNeo4jHealth(): Promise<ServiceHealth> {
  const start = Date.now();
  try {
    const session = driver.session();
    await session.run('RETURN 1');
    await session.close();
    return {
      status: 'connected',
      latency: Date.now() - start
    };
  } catch (error) {
    return {
      status: 'error',
      error: error.message
    };
  }
}

PostgreSQL Health Check​

async function checkPostgresHealth(): Promise<ServiceHealth> {
  const start = Date.now();
  try {
    await pool.query('SELECT 1');
    return {
      status: 'connected',
      latency: Date.now() - start
    };
  } catch (error) {
    return {
      status: 'error',
      error: error.message
    };
  }
}

Status Determination​

function determineOverallStatus(
  services: Record<string, ServiceHealth>
): 'healthy' | 'degraded' | 'unhealthy' {
  const statuses = Object.values(services).map(s => s.status);
  
  // Unhealthy: Stellio (critical service) is down
  if (services.stellio.status !== 'connected') {
    return 'unhealthy';
  }
  
  // Degraded: Any non-critical service is down
  if (statuses.some(s => s !== 'connected')) {
    return 'degraded';
  }
  
  // Healthy: All services connected
  return 'healthy';
}

Kubernetes Probes​

# k8s-deployment.yaml
livenessProbe:
  httpGet:
    path: /api/health
    port: 5000
  initialDelaySeconds: 30
  periodSeconds: 10

readinessProbe:
  httpGet:
    path: /api/health
    port: 5000
  initialDelaySeconds: 5
  periodSeconds: 5

Docker Health Check​

# Dockerfile
HEALTHCHECK --interval=30s --timeout=10s --start-period=5s --retries=3 \
  CMD curl -f http://localhost:5000/api/health || exit 1

Monitoring Integration​

// Prometheus metrics
app.get('/metrics', async (req, res) => {
  const health = await performHealthCheck();
  
  const metrics = `
# HELP service_health Service health status
# TYPE service_health gauge
service_health{service="stellio"} ${health.services.stellio.status === 'connected' ? 1 : 0}
service_health{service="neo4j"} ${health.services.neo4j.status === 'connected' ? 1 : 0}
service_health{service="fuseki"} ${health.services.fuseki.status === 'connected' ? 1 : 0}
service_health{service="postgres"} ${health.services.postgres.status === 'connected' ? 1 : 0}

# HELP service_latency_ms Service response latency in milliseconds
# TYPE service_latency_ms gauge
service_latency_ms{service="stellio"} ${health.services.stellio.latency || 0}
service_latency_ms{service="neo4j"} ${health.services.neo4j.latency || 0}
  `;
  
  res.type('text/plain').send(metrics);
});

References​