I implement a Dashboard functionality that checks every time at program start a list of Requirement-Objects for a bunch of different characteristics like progress, missing data and alike and sets for each characteristic a dedicated beacon on the UI.
protected void initializePerformanceIndicator() {
try {
updateA();
updateB();
...
updateF();
updateG();
} catch (Exception e) {
ErrorHandler.showError("Cannot show KPI Performance", e);
}
}
The checks have different compute demands some are faster some slower, therefore each of this checks runs in a dedicated Task to provide some feedback to the user. The skeleton of such a Task is always the same
protected void updateA() throws Exception {
Task<Void> task = new Task<Void>() {
@Override
protected Void call() throws Exception {
embeddedBudgetKPIController.setHyperlink("Budget", null);
embeddedBudgetKPIController.setToolTip("...");
ObservableList<UserRequirement> issues = FXCollections.observableArrayList();
List<UserRequirement> requirements = reqService.getAllUserRequirements(false); // all requirements of the selected product
for(UserRequirement req: requirements) {
if(*some criteria*) {
issues.add(req);
}
}
if(issues.isEmpty()) {
embeddedBudgetKPIController.setBeaconColor(Color.GREEN);
} else {
embeddedBudgetKPIController.setBeaconColor(Color.RED);
}
return null;
};
};
task.setOnSucceeded(e -> {
// Nothing to do
});
Thread tt = new Thread(task);
tt.start();
}
Before initializePerformanceIndicator is called, I retrieved already elsewhere the data from the database querying a number Spring Repositories:
protected final ObservableList<UserRequirement> allUserRequirements = FXCollections.observableArrayList();
public synchronized ObservableList<UserRequirement> getAllUserRequirements(boolean forceUpdate) throws Exception {
logger.debug(""); // show that this method is called
Product selectedProduct = SelectedScope.getSelectedProduct();
if(selectedProduct == null) {
throw new Exception("No selProduct selected");
}
if(forceUpdate || allUserRequirements.isEmpty()) {
allUserRequirements.clear();
allUserRequirements.addAll(epicRepository.findByProductAndRevisionSuccessorIsNull(selectedProduct));
allUserRequirements.addAll(themeRepository.findByProductAndRevisionSuccessorIsNull(selectedProduct));
allUserRequirements.addAll(userStoryRepository.findByProductAndRevisionSuccessorIsNull(selectedProduct));
allUserRequirements.addAll(tangibleRepository.findByProductAndRevisionSuccessorIsNull(selectedProduct));
}
return allUserRequirements;
}
and as you see updateBudgetKPIController calls getallUserRequirements with the parameter false. Therefore it returns the buffered result set and is not re-fetching data from database. So far everything is fine.
I can run each of these Tasks individually without problem. I tried a number combinations with 2 Tasks. Works fine, but the program will never show more than three or four beacons. Which ones are shown differs as well - what is expected as a consequence of the different Tasks. If I exceed three or four Tasks I often get no error at all, but the UI is just not showing more than three to four beacons.
Sometimes I do get an error message, which is
WARN 08:14 o.h.e.j.s.SqlExceptionHelper.logExceptions:137: SQL Error: 0, SQLState: S1009
ERROR 08:14 o.h.e.j.s.SqlExceptionHelper.logExceptions:142: No operations allowed after statement closed.
I debugged it, and realized that I was generating way too many select statements. The UserRequirement entity has almost a dozen OneToMany relations, some where defined with FetchType.LAZY, so I thought it would be better anyway to configure all these relations as
@OneToMany(fetch = FetchType.LAZY, mappedBy="parent", cascade = CascadeType.ALL)
Because of the LAZY loading, every Task tries to load additional data in the if(*some criteria*) part.
The problem did not disappear but I get more information, as the error is now
WARN 11:02 o.h.c.i.AbstractPersistentCollection.withTemporarySessionIfNeeded:278: Unable to close temporary session used to load lazy collection associated to no session
WARN 11:02 o.h.e.j.s.SqlExceptionHelper.logExceptions:137: SQL Error: 0, SQLState: S1009
ERROR 11:02 o.h.e.j.s.SqlExceptionHelper.logExceptions:142: No operations allowed after statement closed.
So I do have a LAZY loading issue.
I am using Spring Boot 2.1.6, MySQL 8.0.15 Community Server, Hibernate Core {5.3.10.Final}, Java 1.8.0_211 and the com.mysql.cj.jdbc.Driver
From a former issue, I have in my properties file the following configuration
# Prevent LazyInitializationException
spring.jpa.properties.hibernate.enable_lazy_load_no_trans=true
Don't know whether this has a side effect?!
Probably changing the LAZY loading to EAGER will fix it - haven't tried yet - but it would delay program start significantly. Therefore I would prefer a solution with LAZY loading.
Any ideas? I also appreciate any ideas regarding how to further isolate the root cause as the error message is not really explicit and I can't see which part of my code triggers it. Plus when I debug it, the behavior changes as I compute all Tasks sequentially rather then in parallel. Thank you in advance.
