public class SessionCustomizerImpl implements org.eclipse.persistence.config.SessionCustomizer {

    private final static String WSREP_SYNC_WAIT_CHECK_SQL = "SHOW SESSION VARIABLES LIKE 'wsrep_sync_wait'";
    private final static String WSREP_SYNC_WAIT_SET_SQL = "SET SESSION wsrep_sync_wait = 1";

    @Override
    public void customize(Session session) throws Exception {
        Vector result = session.executeSQL(WSREP_SYNC_WAIT_CHECK_SQL);
        if ((result != null) && !result.isEmpty()) {
            session.executeNonSelectingSQL(WSREP_SYNC_WAIT_SET_SQL);
            // Galera connection detected; wsrep_sync_wait set to 1
        } else {
            // No Galera connection detected; wsrep_sync_wait not set
        }

    }
}

public class SyncWaitEntityManagerFactory implements Factory<EntityManager> {
    private final EntityManagerFactory emf;

    @Inject
    public SyncWaitEntityManagerFactory(EntityManagerFactory emf) {
        this.emf = emf;
    }

    @Override
    public EntityManager provide() {
        final EntityManager em = emf.createEntityManager();
        // set it
        em.getTransaction().begin();
        em.createNativeQuery("SET SESSION wsrep_sync_wait = 1").executeUpdate();
        em.getTransaction().commit();

        return em;
    }

    @Override
    public void dispose(EntityManager instance) {
        if (instance.isOpen()) {
            instance.close();
        }
    }

}

String jdbcUrl = "jdbc:mysql://db.example.test:3306/"+ JDBC_DB
            +"?sessionVariables=wsrep_sync_wait=1";
    Properties p = new Properties();
    p.put("javax.persistence.jdbc.url", jdbcUrl);
    p.put("javax.persistence.jdbc.user", JDBC_USER);
    p.put("javax.persistence.jdbc.password", JDBC_PASSWORD);
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("myPU", p);

    EntityManager entityManager = emf.createEntityManager();