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Akka references increasing constantly with Play Framework

I have changed all my multi-thread actions in my application to Akka a few weeks ago.
However, since it seems that I am starting to run out of Heap space (after a week or so).
By basically looking at all actors with
ActorSelection selection = getContext().actorSelection("/*");
the number of actors seems to increase all the time. After an hour of running I have more then 2200. They are called like:
akka://application/user/$Aic
akka://application/user/$Alb
akka://application/user/$Alc
akka://application/user/$Am
akka://application/user/$Amb
I also noticed that when opening websockets (and closing them) there are these:
akka://application/system/Materializers/StreamSupervisor-2/flow-21-0-unnamed
akka://application/system/Materializers/StreamSupervisor-2/flow-2-0-unnamed
akka://application/system/Materializers/StreamSupervisor-2/flow-27-0-unnamed
akka://application/system/Materializers/StreamSupervisor-2/flow-23-0-unnamed
Is there something specific that I need to do to close them and let them be cleaned?
I am not sure the memory issue is related, but the fact that there seem so many after an hour on the production server it could be.
[EDIT: added the code to analyse/count the actors]
public class RetrieveActors extends AbstractActor {
private String identifyId;
private List<String> list;
public RetrieveActors(String identifyId) {
Logger.debug("Actor retriever identity: " + identifyId);
this.identifyId = identifyId;
}
#Override
public Receive createReceive() {
Logger.info("RetrieveActors");
return receiveBuilder()
.match(String.class, request -> {
//Logger.info("Message: " + request + " " + new Date());
if(request.equalsIgnoreCase("run")) {
list = new ArrayList<>();
ActorSelection selection = getContext().actorSelection("/*");
selection.tell(new Identify(identifyId), getSelf());
//ask(selection, new Identify(identifyId), 1000).thenApply(response -> (Object) response).toCompletableFuture().get();
} else if(request.equalsIgnoreCase("result")) {
//Logger.debug("Run list: " + list + " " + new Date());
sender().tell(list, self());
} else {
sender().tell("Wrong command: " + request, self());
}
}).match(ActorIdentity.class, identity -> {
if (identity.correlationId().equals(identifyId)) {
ActorRef ref = identity.getActorRef().orElse(null);
if (ref != null) { // to avoid NullPointerExceptions
// Log or store the identity of the actor who replied
//Logger.info("The actor " + ref.path().toString() + " exists and has replied!");
list.add(ref.path().toString());
// We want to discover all children of the received actor (recursive traversal)
ActorSelection selection = getContext().actorSelection(ref.path().toString() + "/*");
selection.tell(new Identify(identifyId), getSelf());
}
}
sender().tell(list.toString(), self());
}).build();
}
}

Updating a table when clicking on an element from another table

I need to show elements on a table depending on the element (Person) clicked on another table. The problem is that, using a Service, if the user clicks on two elements of the first table very quickly, the data of the two elements is showed in the table, and I only want to show the data from the last one clicked. Hope you can help me.
Here is my code:
personTable.getSelectionModel().selectedItemProperty().addListener(
(observable, oldValue, newValue) -> {
try {
contactoTable.setPlaceholder(new Label("Cargando..."));
showPersonDetails(newValue);
} catch (SQLException ex) {
Logger.getLogger(PersonOverviewController.class.getName()).log(Level.SEVERE, null, ex);
}
});
And showPersonDatails:
contactoTable.setVisible(true);
contactoTable.getItems().clear();
firstNameLabel.setText(person.getFirstName());
lastNameLabel.setText(person.getLastName());
mailLabel.setText(person.getMail());
phoneLabel.setText(person.getPhone());
descriptionLabel.setText(person.getDescription());
service = new Service<Void>() {
#Override
protected Task<Void> createTask() {
return new Task<Void>() {
#Override
protected Void call() throws Exception {
//Background work
DBManager db = new DBManager();
String query = "SELECT * FROM eventos";
ResultSet r = db.executeSelect(query);
contactoTable.getItems().clear();
contactoData.clear();
while (r.next()) {
String q = "SELECT * FROM " + r.getString("Nombre").replace(" ", "_") + " WHERE Nombre = '" + person.getFirstName() + "' AND Apellidos = '" + person.getLastName() + "' AND Correo = '" + person.getMail() + "'";
ResultSet result = db.executeSelect(q);
while (result.next()) {
contactoData.add(new Row(r.getString("Nombre"), result.getString("Asistencia")));
}
}
final CountDownLatch latch = new CountDownLatch(1);
Platform.runLater(() -> {
try {
//FX Stuff done here
contactoTable.setPlaceholder(new Label("No invitado a ningún evento"));
contactoTable.setItems(contactoData);
} finally {
latch.countDown();
}
});
latch.await();
//Keep with the background work
return null;
}
};
}
};
service.start();

You are referencing the same data list (contactoData) from multiple threads, with apparently no synchronization on the list. If the user selects two different items in rapid succession, you launch a service for each one, each service running its task in a different thread. Consequently you have no control over the order the two different threads perform their (multiple) manipulations on contactoData. For example, it is possible (even probable) that the order for two services executing asynchronously is:
First service clears the list
Second service clears the list
First service adds elements to the list
Second service adds elements to the list
and in this case the list contains elements generated by both services, not just one of them.
So you should have your tasks operate on, and return, a new list they create. Then process that list on the FX Application Thread.
It's also not clear why you need a service here, as you only seem to ever use each service once. You may as well just use a task directly.
You also probably want to ensure that the last selection is the one displayed. Since the tasks are running asynchronously, it's possible that if two tasks were started in quick succession, the second would complete before the first. This would result in the second selection being displayed, and then the first selection replacing it. You can avoid this by doing the UI update in an onSucceeded handler, and canceling any current task when you start a new one (thus preventing the currently-executing task from invoking its onSucceeded handler).
Finally, it's really not clear to me why you are making the task wait until the UI is updated.
Here is an updated version of your code:
private Task<List<Row>> updateContactTableTask ;
// ...
private void showPersonDetails(Person person) {
contactoTable.getItems().clear();
firstNameLabel.setText(person.getFirstName());
lastNameLabel.setText(person.getLastName());
mailLabel.setText(person.getMail());
phoneLabel.setText(person.getPhone());
descriptionLabel.setText(person.getDescription());
if (updateContactTableTask != null && updateContactTableTask.isRunning()) {
updateContactTableTask.cancel();
}
updateContactTableTask = new Task<List<Row>>() {
#Override
protected List<Row> call() throws Exception {
List<Row> resultList = new ArrayList<>() ;
//Background work
DBManager db = new DBManager();
String query = "SELECT * FROM eventos";
ResultSet r = db.executeSelect(query);
// quit if we got canceled here...
if (isCancelled()) {
return resultList;
}
while (r.next() && ! isCancelled()) {
// Note: building a query like this is inherently unsafe
// You should use a PreparedStatement in your DBManager class instead
String q = "SELECT * FROM " + r.getString("Nombre").replace(" ", "_") + " WHERE Nombre = '" + person.getFirstName() + "' AND Apellidos = '" + person.getLastName() + "' AND Correo = '" + person.getMail() + "'";
ResultSet result = db.executeSelect(q);
while (result.next()) {
resultList.add(new Row(r.getString("Nombre"), result.getString("Asistencia")));
}
}
return resultList ;
}
};
updateContactTableTask.setOnSucceeded(e -> {
// not really clear you still need contactoData, but if you do:
contactoData.setAll(updateContactTableTask.getValue());
contactoTable.setPlaceholder(new Label("No invitado a ningún evento"));
contactoTable.setItems(contactoData);
});
updateContactTableTask.setOnFailed(e -> {
// handle database errors here...
});
new Thread(updateContactTableTask).start();
}
As an aside, it's not clear to me if, and if so, how, you are closing your database resources. E.g. the result sets never seem to get closed. This could cause resource leaks. However this is incidental to the question (and relies on knowing how your DBManager class is implemented), so I won't address it here.

Java ExecutorService Runnable doesn't update value

I'm using Java to download HTML contents of websites whose URLs are stored in a database. I'd like to put their HTML into database, too.
I'm using Jsoup for this purpose:
public String downloadHTML(String byLink) {
String htmlInPage = "";
try {
Document doc = Jsoup.connect(byLink).get();
htmlInPage = doc.html();
} catch (org.jsoup.UnsupportedMimeTypeException e) {
// process this and some other exceptions
}
return htmlInPage;
}
I'd like to download websites concurrently and use this function:
public void downloadURL(int websiteId, String url,
String categoryName, ExecutorService executorService) {
executorService.submit((Runnable) () -> {
String htmlInPage = downloadHTML(url);
System.out.println("Category: " + categoryName + " " + websiteId + " " + url);
String insertQuery =
"INSERT INTO html_data (website_id, html_contents) VALUES (?,?)";
dbUtils.query(insertQuery, websiteId, htmlInPage);
});
}
dbUtils is my class based on Apache Commons DbUtils. Details are here: http://pastebin.com/iAKXchbQ
And I'm using everything mentioned above in a such way: (List<Object[]> details are explained on pastebin, too)
public static void main(String[] args) {
DbUtils dbUtils = new DbUtils("host", "db", "driver", "user", "pass");
List<String> categoriesList =
Arrays.asList("weapons", "planes", "cooking", "manga");
String sql = "SELECT lw.id, lw.website_url, category_name " +
"FROM list_of_websites AS lw JOIN list_of_categories AS lc " +
"ON lw.category_id = lc.id " +
"where category_name = ? ";
ExecutorService executorService = Executors.newFixedThreadPool(10);
for (String category : categoriesList) {
List<Object[]> sitesInCategory = dbUtils.select(sql, category );
for (Object[] entry : sitesInCategory) {
int websiteId = (int) entry[0];
String url = (String) entry[1];
String categoryName = (String) entry[2];
downloadURL(websiteId, url, categoryName, executorService);
}
}
executorService.shutdown();
}
I'm not sure if this solution is correct but it works. Now I want to modify code to save HTML not from all websites in my database, but only their fixed ammount in each category.
For example, download and save HTML of 50 websites from the "weapons" category, 50 from "planes", etc. I don't think it's necessary to use sql for this purpose: if we select 50 sites per category, it doesn't mean we save them all, because of possibly incorrect syntax and connection problems.
I've tryed to create separate class implementing Runnable with fields: counter and maxWebsitesPerCategory, but these variables aren't updated. Another idea was to create field Map<String,Integer> sitesInCategory instead of counter, put each category as a key there and increment its value until it reaches maxWebsitesPerCategory, but it didn't work, too. Please, help me!
P.S: I'll also be grateful for any recommendations connected with my realization of concurrent downloading (I haven't worked with concurrency in Java before and this is my first attempt)

How about this?
for (String category : categoriesList) {
dbUtils.select(sql, category).stream()
.limit(50)
.forEach(entry -> {
int websiteId = (int) entry[0];
String url = (String) entry[1];
String categoryName = (String) entry[2];
downloadURL(websiteId, url, categoryName, executorService);
});
}
sitesInCategory has been replaced with a stream of at most 50 elements, then your code is run on each entry.
EDIT
In regard to comments. I've gone ahead and restructured a bit, you can modify/implement the content of the methods I've suggested.
public void werk(Queue<Object[]> q, ExecutorService executorService) {
executorService.submit(() -> {
try {
Object[] o = q.remove();
try {
String html = downloadHTML(o); // this takes one of your object arrays and returns the text of an html page
insertIntoDB(html); // this is the code in the latter half of your downloadURL method
}catch (/*narrow exception type indicating download failure*/Exception e) {
werk(q, executorService);
}
}catch (NoSuchElementException e) {}
});
}
^^^ This method does most of the work.
for (String category : categoriesList) {
Queue<Object[]> q = new ConcurrentLinkedQueue<>(dbUtils.select(sql, category));
IntStream.range(0, 50).forEach(i -> werk(q, executorService));
}
^^^ this is the for loop in your main
Now each category tries to download 50 pages, upon failure of downloading a page it moves on and tries to download another page. In this way, you will either download 50 pages or have attempted to download all pages in the category.

Created documents are not versionable

I use OpenCmis in-memory for testing. But when I create a document I am not allowed to set the versioningState to something else then versioningState.NONE.
The doc created is not versionable some way... I used the code from http://chemistry.apache.org/java/examples/example-create-update.html
The test method:
public void test() {
String filename = "test123";
Folder folder = this.session.getRootFolder();
// Create a doc
Map<String, Object> properties = new HashMap<String, Object>();
properties.put(PropertyIds.OBJECT_TYPE_ID, "cmis:document");
properties.put(PropertyIds.NAME, filename);
String docText = "This is a sample document";
byte[] content = docText.getBytes();
InputStream stream = new ByteArrayInputStream(content);
ContentStream contentStream = this.session.getObjectFactory().createContentStream(filename, Long.valueOf(content.length), "text/plain", stream);
Document doc = folder.createDocument(
properties,
contentStream,
VersioningState.MAJOR);
}
The exception I get:
org.apache.chemistry.opencmis.commons.exceptions.CmisConstraintException: The versioning state flag is imcompatible to the type definition.
What am I missing?

I found the reason...
By executing the following code I discovered that the OBJECT_TYPE_ID 'cmis:document' don't allow versioning.
Code to view all available OBJECT_TYPE_ID's (source):
boolean includePropertyDefintions = true;
for (t in session.getTypeDescendants(
null, // start at the top of the tree
-1, // infinite depth recursion
includePropertyDefintions // include prop defs
)) {
printTypes(t, "");
}
static void printTypes(Tree tree, String tab) {
ObjectType objType = tree.getItem();
println(tab + "TYPE:" + objType.getDisplayName() +
" (" + objType.getDescription() + ")");
// Print some of the common attributes for this type
print(tab + " Id:" + objType.getId());
print(" Fileable:" + objType.isFileable());
print(" Queryable:" + objType.isQueryable());
if (objType instanceof DocumentType) {
print(" [DOC Attrs->] Versionable:" +
((DocumentType)objType).isVersionable());
print(" Content:" +
((DocumentType)objType).getContentStreamAllowed());
}
println(""); // end the line
for (t in tree.getChildren()) {
// there are more - call self for next level
printTypes(t, tab + " ");
}
}
This resulted in a list like this:
TYPE:CMIS Folder (Description of CMIS Folder Type) Id:cmis:folder
Fileable:true Queryable:true
TYPE:CMIS Document (Description of CMIS Document Type)
Id:cmis:document Fileable:true Queryable:true [DOC Attrs->]
Versionable:false Content:ALLOWED
TYPE:My Type 1 Level 1 (Description of My Type 1 Level 1 Type)
Id:MyDocType1 Fileable:true Queryable:true [DOC Attrs->]
Versionable:false Content:ALLOWED
TYPE:VersionedType (Description of VersionedType Type)
Id:VersionableType Fileable:true Queryable:true [DOC Attrs->]
Versionable:true Content:ALLOWED
As you can see the last OBJECT_TYPE_ID has versionable: true... and when I use that it does work.

How to Access the printer queue within java

Suppose that I printed some documents from a program like MS Word. Let's say I selected 4 documents at once, so three of them would end up waiting in the printer queue. I would like to access and read some information about the documents waiting in the queue. In other words, how can I access the printer queue and read information about any pending files with java?
Is there a way to do that? If so, how can I do it?
Thanks for the help

maybe this function helpful for you.
public Integer getExistQueuePrinter() {
int queue = 0;
PrintService myService = null;
PrintService printService = PrintServiceLookup.lookupDefaultPrintService();
if (printService != null) {
//--> set printService.
myService = printService;
//--> get attributes from printService.
AttributeSet attributes = printService.getAttributes();
//--> loop attributes.
for (Attribute a : attributes.toArray()) {
String name = a.getName();
String value = attributes.get(a.getClass()).toString();
//System.out.println(name + " : " + value);
if (name.equals("queued-job-count")) {
//System.out.println(name + " : " + value);
queue = Integer.parseInt(value);
}
}
Object[] obj = attributes.toArray();
//System.out.println("queue = " + obj[3]);
return queue;
/* debug.
for (Object value : obj) {
System.out.println("Color = " + value);
}
*/
}
return null;
}

Here you can find complete code for accessing printer through java code.
it provides functionality like
cancel print job,
display print dialog,
print file etc..
http://anonsvn.icesoft.org//repo/icepdf/tags/icepdf-3.1.0/icepdf/viewer/src/org/icepdf/ri/common/PrintHelper.java