Hi,
The mailbox-store provides base/common logic to all stores.
There seems to be a trend to add more shared functions in it, namely:
1.- LastUidTracker replacing the getLastUid() method that was
implemented in each store.
2.-MailboxPathLocker used when creating/renaming mailbox. The extra
classes really brings bring ease when reading code and allows
implementation for distributed locking.
3.- MailboxIndex for search optimization (ongoing work)
I was also thinking to a 4th area, the UID management (UidProvider) we
talked before on https://issues.apache.org/jira/browse/IMAP-193.
Currently, UID are assigned by the store impl (if you use JPA, it must
be JPA and so on...). This is done in different ways (see code after for
jpa/jcr/maidir).
We could define a UidProvider to get rid of different locking mechanism
and have an efficient and distributed way to manage/generate the UIDs.
JPA/JCR/... and could benefit from this default implementation. (JPA
could probably be ameliorated with a auto_increment rather than a
database lock to manage the UID, but I think there will be a non-optimum
usage of the key space).
We may also discuss a layer implementing distributed MailboxListeners
(to have a base for distributed James, and transfer the needed
LastUidTracker,... events).
Are there any other areas we could define as the mailbox-store
responsibility?
Tks,
Eric
Locking for new UID for JPAMessageMapper
======================================
protected long reserveUid(JPAMailbox mailbox) {
EntityManager manager = getEntityManager();
// we need to set a pessimistic write lock to be sure we don't
get any problems with dirty reads etc.
JPAMailbox m = manager.find(JPAMailbox.class,
mailbox.getMailboxId(), LockModeType.PESSIMISTIC_WRITE);
manager.refresh(m);
m.consumeUid();
manager.persist(m);
return m.getLastUid();
}
}
Locking for new UID for JCRMessageMapper
=======================================
protected long reserveNextUid(Mailbox<String> mailbox) throws
RepositoryException, InterruptedException {
long result = getNodeLocker().execute(new
NodeLocker.NodeLockedExecution<Long>() {
public Long execute(Node node) throws RepositoryException {
Property uidProp =
node.getProperty(JCRMailbox.LASTUID_PROPERTY);
long uid = uidProp.getLong();
uid++;
uidProp.setValue(uid);
uidProp.getSession().save();
return uid;
}
public boolean isDeepLocked() {
return true;
}
}, getSession().getNodeByIdentifier(mailbox.getMailboxId()),
Long.class);
return result;
}
Locking for new UID for MaildirMessageMapper (in MaildirFolder)
=========================================================
/**
* Locks the uidList file and if it has retrieved the lock, returns it.
* Make sure to call unlockUidList() in a finally block afterwards.
* @return The locked uidList
*/
public File lockUidList() {
FileLock.lock(uidFile);
return uidFile;
}
/**
* Unlocks the uidList file if it has been locked before.
*/
public void unlockUidList() {
FileLock.unlock(uidFile);
}
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