Health Checks & Monitoring in ASP.NET Core
💡 Concept Name
Health Checks & Monitoring in ASP.NET Core
📘 Quick Intro
Health checks in ASP.NET Core help expose the health of your application via endpoints. They're essential for uptime, observability, and diagnostics. Commonly used in cloud-native and microservices setups.
🧠 Analogy / Short Story
Imagine your app as a patient in a hospital. Health checks are like periodic medical tests (heartbeat, blood pressure) to ensure vital signs are normal. If something’s off, the monitoring system alerts the doctor (devs or ops) instantly.
🔧 Technical Explanation
ASP.NET Core provides `Microsoft.AspNetCore.Diagnostics.HealthChecks` to add health endpoints.
You register checks in `Program.cs` using `AddHealthChecks()` and map them with `MapHealthChecks("/health")`.
You can check memory, database connection, custom services, and even use tags for readiness/liveness probes in Kubernetes.
🎯 Purpose & Use Case
- ✅ Expose liveness/readiness status for Kubernetes probes
- ✅ Monitor database, cache, or external services availability
- ✅ Integrate with Prometheus, Grafana, Azure Monitor
- ✅ Gracefully drain unhealthy instances
- ✅ Enable proactive maintenance and alerting
💻 Real Code Example
// Program.cs (ASP.NET Core 6+)
var builder = WebApplication.CreateBuilder(args);
builder.Services.AddHealthChecks()
.AddSqlServer(builder.Configuration.GetConnectionString("DefaultConnection"));
var app = builder.Build();
app.MapHealthChecks("/health");
app.Run();
❓ Interview Q&A
Q1: What namespace is used for health checks?
A: Microsoft.AspNetCore.Diagnostics.HealthChecks
Q2: What is the default path to expose health?
A: It's usually `/health` or `/healthz`
Q3: Can I create custom health checks?
A: Yes, by implementing `IHealthCheck`.
Q4: What's the purpose of tags in health checks?
A: To filter checks for specific probes like readiness or liveness.
Q5: Are health checks async?
A: Yes, all checks are `Task`-based for async support.
Q6: Can we return custom responses?
A: Yes, by providing a custom `HealthCheckOptions.ResponseWriter`.
Q7: How to monitor Redis health?
A: Use `.AddRedis()` in the health check registration.
Q8: Is it possible to secure health endpoints?
A: Yes, with authentication/authorization middleware.
Q9: What HTTP status code means unhealthy?
A: Typically 503 (Service Unavailable).
Q10: Can health checks help with autoscaling?
A: Yes, they indicate instance readiness/unhealthiness for orchestration systems.
📝 MCQs
Q1: What is the primary use of health checks?
- A. Load testing
- B. UI Testing
- C. Monitor app health
- D. Logging requests
Q2: Which method adds health check services?
- A. AddHealthChecks()
- B. AddMonitoring()
- C. UseHealthStatus()
- D. ConfigureHealth()
💡 Bonus Insight
Tag-based filtering in ASP.NET Core health checks lets you categorize checks for readiness vs liveness — a critical feature when deploying in Kubernetes or Docker Swarm.
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