server/data/data-jpa/src/main/java/org/apache/james/jpa/healthcheck/JPAHealthCheck.java

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package org.apache.james.jpa.healthcheck;

import static org.apache.james.core.healthcheck.Result.healthy;
import static org.apache.james.core.healthcheck.Result.unhealthy;

import javax.inject.Inject;
import javax.persistence.EntityManagerFactory;

import org.apache.james.backends.jpa.EntityManagerUtils;
import org.apache.james.core.healthcheck.ComponentName;
import org.apache.james.core.healthcheck.HealthCheck;
import org.apache.james.core.healthcheck.Result;

import reactor.core.publisher.Mono;
import reactor.core.scheduler.Schedulers;

public class JPAHealthCheck implements HealthCheck {

    private final EntityManagerFactory entityManagerFactory;

    @Inject
    public JPAHealthCheck(EntityManagerFactory entityManagerFactory) {
        this.entityManagerFactory = entityManagerFactory;
    }

    @Override
    public ComponentName componentName() {
        return new ComponentName("JPA Backend");
    }

    @Override
    public Mono<Result> check() {
        return Mono.usingWhen(Mono.fromCallable(entityManagerFactory::createEntityManager).subscribeOn(Schedulers.boundedElastic()),
            entityManager -> {
                if (entityManager.isOpen()) {
                    return Mono.just(healthy(componentName()));
                } else {
                    return Mono.just(unhealthy(componentName(), "entityManager is not open"));
                }
            },
            entityManager -> Mono.fromRunnable(() -> EntityManagerUtils.safelyClose(entityManager)).subscribeOn(Schedulers.boundedElastic()))
            .onErrorResume(IllegalStateException.class,
                e -> Mono.just(unhealthy(componentName(), "EntityManagerFactory or EntityManager thrown an IllegalStateException, the connection is unhealthy", e)))
            .onErrorResume(e -> Mono.just(unhealthy(componentName(), "Unexpected exception upon checking JPA driver", e)));
    }
}