I have a springboot application that implements a user referral system. One use case is that when a user signs up using a valid referral code from another user, the referrer user gets one reward point, and for every five points they get 10$ in credit. According to this, I have implemented a use case in my application that honors these business rules, and to test proper behavior under high concurrency, I've created an integration test using @DataJpaTest and spring data repositories and H2 DB as storage system. In my test, I create a first user, and then I create a certain amount of users using the first user referral code, every one of those users is created on a different thread using a thread pool executor to spawn those threads. My problem is that the users created through thread pool spawned threads don't see the first user created in the main thread, even though I'm using JpaRepository.saveAndFlush() method to save them.
Could someone give me an explanation about what's happening here? Is it because Hibernate's session is not thread-safe?
You can see my code below, the first test has been simplified to just check the amount of user's in the repository.
@DataJpaTest(includeFilters = @ComponentScan.Filter(type = FilterType.ANNOTATION, classes = Repository.class))
public class JpaTest {
@Autowired
private TestEntityManager entityManager;
@Autowired
@Qualifier("JpaUserRepository")
private JpaUserRepository userRepository;
@Autowired
@Qualifier("JpaReferralRepository")
private ReferralRepository referralRepository;
private RegisterReferredUser registerReferredUser;
private CreateUser createUser;
private GetUser getUser;
@BeforeEach
void setUp() {
registerReferredUser = new RegisterReferredUser(referralRepository, userRepository);
createUser = new CreateUser(userRepository, referralRepository, registerReferredUser);
getUser = new GetUser(userRepository);
}
@Test
void createUser_shouldWorksProperlyUnderConcurrentExecution() throws InterruptedException {
ExecutorService executor = Executors.newFixedThreadPool(10);
EmailAddress referrerUserEmail = EmailAddress.of("john.doe@acme.inc");
User referrerUser = createUser.execute(new CreateUserCommand(referrerUserEmail.getValue(), null));
String referralCode = referrerUser.getReferralCode().getValue();
int maxIterations = 10;
for (int i = 0; i < maxIterations; i++) {
int emailSeed = i;
executor.submit(() -> {
createUser.execute(new CreateUserCommand(anEmailAddress(emailSeed), referralCode));
});
}
executor.shutdown();
if (!executor.awaitTermination(20, TimeUnit.SECONDS)) {
fail("Executor didn't finish in time");
}
assertThat(entityManager.getEntityManager().createQuery("from JpaUser").getResultList().size()).isEqualTo(maxIterations + 1);
// This fails: just 1 user in the repository, however, if I register users without referral (without checking the existence of the first user), users are created and this pass
}
@Test
void just_a_POC() throws InterruptedException {
ExecutorService executor = Executors.newFixedThreadPool(10);
userRepository.save(UserMother.aUserWithEmail("john.doe@acme.inc"));
int maxIterations = 10;
for (int i = 0; i < maxIterations; i++) {
int emailSeed = i;
executor.submit(() -> userRepository.save(UserMother.aUserWithEmail(anEmailAddress(emailSeed))));
}
executor.shutdown();
if (!executor.awaitTermination(20, TimeUnit.SECONDS)) {
fail("Executor didn't finish in time");
}
assertThat(entityManager.getEntityManager().createQuery("from JpaUser").getResultList().size()).isEqualTo(maxIterations + 1);
// This pass
}
}
In the CreateUser I have the following code:
private void assertReferralCodeIsValid(ReferralCode referralCode, EmailAddress email) {
if (!userRepository.findByReferralCode(referralCode).isPresent()) {
throw new NonExistentReferralCode(referralCode);
}
if (referralRepository.findByEmailAndCode(email, referralCode).isPresent()) {
throw new ReferralCodeAlreadyUsed(email, referralCode);
}
}
And this is the JpaUserRepository.save() method:
@Repository("JpaUserRepository")
public class JpaUserRepository implements UserRepository {
private JpaUserCrudRepository crudRepository;
public JpaUserRepository(JpaUserCrudRepository crudRepository) {
this.crudRepository = crudRepository;
}
@Override
public void save(User user) {
crudRepository.saveAndFlush(JpaUser.fromDomain(user));
}
}
