Jackrabbit 和并发修改

Question

在我们对使用 jackrabbit 的应用程序进行了一些性能测试之后，我们面临着并发修改 jackrabbit 存储库的巨大问题。当我们在多线程模拟中添加节点或编辑节点时，就会出现问题。然后我编写了非常简单的测试，这表明问题不在我们的环境中。

有它：

简单无状态Bean

     @Stateless
        @Local(TestFacadeLocal.class)
        @Remote(TestFacadeRemote.class)
        public class TestFacadeBean implements TestFacadeRemote, TestFacadeLocal {
            public void doAction(int name) throws Exception {
                new TestSynch().doAction(name);
            }
        }

简单类

    public class TestSynch {
        public void doAction(int name) throws Exception {
            Session session = ((Repository) new InitialContext().
                    lookup("java:jcr/local")).login(
                    new SimpleCredentials("username", "pwd".toCharArray()));
            List added = new ArrayList();
            Node folder = session.getRootNode().getNode("test");
            for (int i = 0; i <= 100; i++) {
                Node child = folder.addNode("" + System.currentTimeMillis(), 
                              "nt:folder");
                child.addMixin("mix:versionable");

                added.add(child);
            }
            // saving butch changes
            session.save();

            //checking in all created nodes
            for (Node node : added) {
                session.getWorkspace().getVersionManager().checkin(node.getPath());
            }
        }
    }

和测试类

    public class Test {
        private int c = 0;
        private int countAll = 50;
        private ExecutorService executor = Executors.newFixedThreadPool(5);

        public ExecutorService getExecutor() {
            return executor;
        }

        public static void main(String[] args) {
            Test test = new Test();
            try {
                test.start();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        private void start() throws Exception {
            long time = System.currentTimeMillis();
            TestFacadeRemote testBean = (TestFacadeRemote) getContext().
                                        lookup( "test/TestFacadeBean/remote");
            for (int i = 0; i < countAll; i++) {
                getExecutor().execute(new TestInstallerThread(i, testBean));
            }

            getExecutor().shutdown();
            while (!getExecutor().isTerminated()) {
                try {
                    Thread.sleep(500);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            System.out.println(c + " shutdown " + 
                               (System.currentTimeMillis() - time));

        }

        class TestInstallerThread implements Runnable {
            private int number = 0;
            TestFacadeRemote testBean;

            public TestInstallerThread(int number, TestFacadeRemote testBean) {
                this.number = number;
                this.testBean = testBean;
            }

            @Override
            public void run() {
                try {
                    System.out.println("Installing data " + number);
                    testBean.doAction(number);
                    System.out.println("STOP" + number);
                } catch (Exception e) {
                    e.printStackTrace();
                    c++;
                }
            }

        }

        public Context getContext() throws NamingException {
            Properties properties = new Properties();
            //init props
            ..............
            return new InitialContext(properties);
        }
    }

如果我用池中的1个线程初始化执行器，则所有操作都完成，没有任何错误。如果我用 5 个线程初始化执行器，有时会出现错误：

在服务器上的客户端上

    java.lang.RuntimeException: javax.transaction.RollbackException: [com.arjuna.ats.internal.jta.transaction.arjunacore.commitwhenaborted] [com.arjuna.ats.internal.jta.transaction.arjunacore.commitwhenaborted] Can't commit because the transaction is in aborted state
        at org.jboss.aspects.tx.TxPolicy.handleEndTransactionException(TxPolicy.java:198)

，一开始就发出警告

    ItemStateReferenceCache [ItemStateReferenceCache.java:176] overwriting cached entry 187554a7-4c41-404b-b6ee-3ce2a9796a70

，然后

    javax.jcr.RepositoryException: org.apache.jackrabbit.core.state.ItemStateException: there's already a property state instance with id 52fb4b2c-3ef4-4fc5-9b79-f20a6b2e9ea3/{http://www.jcp.org/jcr/1.0}created
        at org.apache.jackrabbit.core.PropertyImpl.restoreTransient(PropertyImpl.java:195) ~[jackrabbit-core-2.2.7.jar:2.2.7]
        at org.apache.jackrabbit.core.ItemSaveOperation.restoreTransientItems(ItemSaveOperation.java:879) [jackrabbit-core-2.2.7.jar:2.2.7]

我们尝试同步此方法和其他工作流程，以将多线程调用作为一个线程处理。没有任何帮助。

还有一件事 - 当我们在没有 ejb 层的情况下进行类似的测试时 - 一切都工作正常。 它看起来像是包裹在自己的事务中的容器，然后全部崩溃了。

也许有人遇到过这样的问题。 提前致谢。

Answer 1

来自 Jackrabbit Wiki：

JCR 规范明确指出会话不是线程安全的（JCR 1.0 第 7.5 节和 JCR 2.0 第 4.1.2 节）。因此，Jackrabbit 不支持多个线程同时读取或写入同一会话。每个会话只能从一个线程访问。

...
如果需要并发写入同一个节点，则需要使用多个会话，并使用JCR锁定来确保不发生冲突。