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From: Michael Harrison <michael_harrison@persistent.com>
To: "users@jackrabbit.apache.org" <users@jackrabbit.apache.org>
Subject: Concurrrent use of Repositories
Thread-Topic: Concurrrent use of Repositories
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Date: Tue, 6 Jun 2017 05:26:09 +0000
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We are just starting to use Oak (version 1.6.1) backed by a file store. We h=
ave two concurrent processes trying to access the data in the file store, ea=
ch process using its own Repository interface. As a simple test case we have=
 the following. Process1 has this code (imports omitted to save space):


public class HoldSessionOpen {

    private static String workspace =3D "default";
    private static String repodir =3D "\\tmp\\oak-repo";

    public static void main(String[] args) throws Exception {
        FileStore filestore =3D FileStoreBuilder.fileStoreBuilder(new File(r=
epodir)).build();
        try {
            SegmentNodeStore sns =3D SegmentNodeStoreBuilders.builder(filest=
ore).build();
            Repository repository =3D new Jcr(new Oak(sns)).createRepository=
();
            SimpleCredentials creds =3D new SimpleCredentials("admin", "admi=
n".toCharArray());
            Session session =3D repository.login(creds, workspace);
            try {
                System.out.println("Holding session: " + session);
                Node root =3D session.getRootNode();
                for (int i =3D 0; i < 100000; i++) {
                    if (root.hasNode("hold")) {
                        Node hold =3D root.getNode("hold");
                        long count =3D hold.getProperty("count").getLong();
                        hold.setProperty("count", count + 1);
                        System.out.println("found the hold node, count =3D "=
 + count);
                    } else {
                        System.out.println("creating the hold node");
                        root.addNode("hold").setProperty("count", 1);
                    }
                }
                session.save();
            } finally {
                session.logout();
            }
        } finally {
            filestore.flush();
            filestore.close();
        }
    }
}


and process2 has this code:


public class AccessRepo {

    private static String workspace =3D "default";
    private static String repodir =3D "\\tmp\\oak-repo";

    public static void main(String[] args) throws Exception {
        FileStore filestore =3D FileStoreBuilder.fileStoreBuilder(new File(r=
epodir)).build();
        try {
            SegmentNodeStore sns =3D SegmentNodeStoreBuilders.builder(filest=
ore).build();
            Repository repository =3D new Jcr(new Oak(sns)).createRepository=
();
            SimpleCredentials creds =3D new SimpleCredentials("admin", "admi=
n".toCharArray());
            Session session =3D repository.login(creds, workspace);
            try {
                Node root =3D session.getRootNode();
                if (root.hasNode("hello")) {
                    Node hello =3D root.getNode("hello");
                    long count =3D hello.getProperty("count").getLong();
                    hello.setProperty("count", count + 1);
                    System.out.println("found the hello node, count =3D " +=
 count);
                } else {
                    System.out.println("creating the hello node");
                    root.addNode("hello").setProperty("count", 1);
                }
                session.save();
            } finally {
                session.logout();
            }
        } finally {
            filestore.flush();
            filestore.close();
        }
    }
}

If I open up two consoles and start process1 in one and then process2 in the=
 other, process2 is blocked until process1 terminates.


The actual use case is that one process is responding to REST requests for d=
ata in the repository while another process is uploading content to the same=
 repository, but we see the same behavior - the process that starts second i=
s blocked until the process that starts first completes.


Is there any way to have concurrent access to the same data through two repo=
sitories?


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