Jena transaction isolation not working

[alb3rtino]

I have set DefaultIsolation = 8 in the parameters section of virtuoso.ini like described here.
Following runnable class reads a value and increments it by 1 inside a transaction:

class IncrementThread implements Runnable {
  @Override
  public void run() {
    Dataset ds = new VirtDataset("localhost:1111", "dba", "dba");
    ds.begin(ReadWrite.WRITE);
    try {
      Statement s = ds.getNamedModel(GRAPH).createResource(RES).getProperty(RDFS.label);
      int i = s.getLiteral().getInt();
      System.out.println(Thread.currentThread() + " reading value: " + i + ", writing value: " + ++i);
      s.changeLiteralObject(i);
      ds.commit();
    } catch (Exception e) {
      e.printStackTrace();
    } finally {
      ds.end();
    }
    ds.close();
  }
}

now when running 5 threads:

public void start() {
  // clear graph, set value initial value to 0
  Dataset ds = new VirtDataset("localhost:1111", "dba", "dba");
  Model m = ds.getNamedModel(GRAPH);
  m.removeAll();
  m.createResource(RES).addProperty(RDFS.label, m.createTypedLiteral(0));
  ds.close();
  // run threads
  for (int i = 1; i <= 5; i++) {
    Thread t = new Thread(new IncrementThread());
    t.start();
  }
}

the output is something similar to this:

Thread[Thread-2,5,main] reading value: 0, writing value: 1
Thread[Thread-3,5,main] reading value: 0, writing value: 1
Thread[Thread-1,5,main] reading value: 0, writing value: 1
Thread[Thread-4,5,main] reading value: 0, writing value: 1
Thread[Thread-5,5,main] reading value: 1, writing value: 2

when it should be something like this:

Thread[Thread-1,5,main] reading value: 0, writing value: 1
Thread[Thread-2,5,main] reading value: 1, writing value: 2
Thread[Thread-3,5,main] reading value: 2, writing value: 3
Thread[Thread-5,5,main] reading value: 3, writing value: 4
Thread[Thread-4,5,main] reading value: 4, writing value: 5

[smalinin]

Jena provider uses TRANSACTION_READ_COMMITTED always.
It is hardcoded in VirtTransactionHandler.java and it doesn't use the Default Isolation

[alb3rtino]

and are there any plans on supporting the other transaction modes as well?

[smalinin]

Support for set IsolationLevel was added to VirtDataset class, it will be in Git soon.
Example:

        VirtDataset ds = new VirtDataset("localhost:1111", "dba", "dba");

        ds.setIsolationLevel(VirtIsolationLevel.SERIALIZABLE);

[H-B-Schmidt]

Will this happen really soon ?

[smalinin]

jena3_src.zip
Some delay with updating git, please use the attached virt_jena3.jar (in zip with sources)

[H-B-Schmidt]

So without setting ds.setIsolationLevel() the jena provider is now using the server setting for isolation ?

[alb3rtino]

did you test this? when i'm applying the changes from the provided zip and setting

ds.setIsolationLevel(VirtIsolationLevel.SERIALIZABLE);

i keep getting a

virtuoso.jdbc4.VirtuosoException: SR172: Transaction deadlocked

exception and virtuoso keeps telling me:

12:31:24 WARNING: * Monitor: Should read for update because lock escalation from shared to exclusive fails frequently (1)
12:31:24 WARNING: * Monitor: Should read for update because lock escalation from shared to exclusive fails frequently (2)

[smalinin]

I didn't play with your example. I tested Jena provider, that it set properly isolation level for connection. The one update in RDF storage could change many data, it doesn't look like update in an one SQL table.
Note the next:

1. Jena provider use mode log_enable=1 by default, if you don't use log_enable option in the URL connection string

2. You could change Concurrency mode for SPARUL queries and graph Insert/Update/Delete operations.
   The supported concurrency modes:
   VirtGraph.CONCUR_DEFAULT
   VirtGraph.CONCUR_PESSIMISTIC
   VirtGraph.CONCUR_OPTIMISTIC

Example:

        VirtDataset ds = new VirtDataset("localhost:1111", "dba", "dba");
        ds.setConcurrencyMode(VirtGraph.CONCUR_PESSIMISTIC);

Try to use VirtGraph.CONCUR_PESSIMISTIC mode.
The default concurrency mode works better with readonly operations.

[H-B-Schmidt]

Will the provided jena3_src.zip find its way into this repository soon ?

[smalinin]

It looks, that patch for Git was missed. The fix has been added and Git sources was updated.