Untitled :: Red Hat build of Quarkus on Red Hat OpenShift

Negative Health Checks

In this section we create another health check which simulates a connection to an external service provider such as a database. For simplicity reasons, we’ll use an application.properties setting to toggle the health check from DOWN to UP.

Create another Java class in the same package called DatabaseConnectionHealthCheck.java with the following code:

package org.acme.people.health;

import org.eclipse.microprofile.config.inject.ConfigProperty;
import org.eclipse.microprofile.health.HealthCheck;
import org.eclipse.microprofile.health.HealthCheckResponse;
import org.eclipse.microprofile.health.HealthCheckResponseBuilder;
import org.eclipse.microprofile.health.Liveness;

import jakarta.enterprise.context.ApplicationScoped;

@ApplicationScoped
@Liveness
public class DatabaseConnectionHealthCheck implements HealthCheck {

    @ConfigProperty(name = "database.up", defaultValue = "false")
    public boolean databaseUp;

    @Override
    public HealthCheckResponse call() {

        HealthCheckResponseBuilder responseBuilder = HealthCheckResponse.named("Database connection health check");

        try {
            simulateDatabaseConnectionVerification();
            responseBuilder.up();
        } catch (IllegalStateException e) {
            // cannot access the database
            responseBuilder.down()
                    .withData("error", e.getMessage());
        }

        return responseBuilder.build();
    }

    private void simulateDatabaseConnectionVerification() {
        if (!databaseUp) {
            throw new IllegalStateException("Cannot contact database");
        }
    }
}

Re-run the health check test:

curl -i http://localhost:8080/q/health/live

You should see at the beginning the HTTP response:
```
HTTP/1.1 503 Service Unavailable
```
The returned content should begin with "status": "DOWN" and you should see in the checks array the newly added Database connection health check which is down and the error message explaining why it failed:
```
        {
            "name": "Database connection health check",
            "status": "DOWN",
            "data": {
                "error": "Cannot contact database"
            }
        },
```

Fix Health Check

We shouldn’t leave this application with a health check in DOWN state.

Since we are running Quarkus dev mode, add this to to the end of the src/main/resources/application.properties file:
```
database.up=true
```

Access the health check again using the same curl command - it should be UP!

curl -i http://localhost:8080/q/health/live

    {
        "name": "Database connection health check",
        "status": "UP"
    }