Re: [Exist-open] read-only access to database?

[Pierrick B. <pie...@cu...>]

Hi again,

Ron Van den Branden wrote:

> Ok,  here is the complete console window output I get (pardon my Java,=20
> or lack thereof):
>=20
> cluster.journal.maxStore 65000
> cluster.journal.shift 100
> configuration error: null
> java.nio.channels.NonWritableChannelException
>        at sun.nio.ch.FileChannelImpl.tryLock(FileChannelImpl.java:818)
>        at java.nio.channels.FileChannel.tryLock(FileChannel.java:967)
>        at org.exist.storage.btree.Paged.setFile(Paged.java:407)

Well, I'm quite puzzled with this code=20
(http://cvs.sourceforge.net/viewcvs.py/exist/eXist-1.0/src/org/exist/stor=
age/btree/Paged.java?annotate=3D1.12,=20
lines 395-415) :

protected final void setFile(final File file) throws DBException {
   this.file =3D file;
   fileIsNew =3D !file.exists();
   try {
     if ((!file.exists()) || file.canWrite()) {
       raf =3D new RandomAccessFile(file, "rw");
     } else {
       readOnly =3D true;
       raf =3D new RandomAccessFile(file, "r");
     }		=09
     FileChannel channel =3D raf.getChannel();		=09
     if (channel.tryLock() =3D=3D null)
       readOnly =3D true;
       //throw new DBException("Failed to open database file: " +=20
file.getAbsolutePath() +
       //". It is locked by another process.");
   } catch (IOException e) {
     LOG.warn("An exception occured while opening database file " +=20
file.getAbsolutePath() + ": " + e.getMessage(), e);
   }
}

First, notice the commented exception ;-)

Then, I find strange to try a lock on a file if it has a *known*=20
read-only access. I would move this try just after :
raf =3D new RandomAccessFile(file, "rw");

... possible in another try/catch block that would reopen the file in=20
"r" mode.

Then, I find strange to test whether the file is read-only or not : the=20
Broker should already know it ! ... and eventually detect=20
inconsistencies between the configuration and the file system.

Then, who is supposed to release the lock ?

As a quick fix, I would move :

FileChannel channel =3D raf.getChannel();		=09
if (channel.tryLock() =3D=3D null)
   readOnly =3D true;

just after :
raf =3D new RandomAccessFile(file, "rw");

Can anybody test ?

>> I'm afraid that we also lack test cases in this area...
>>
> (I can attest that it used to work in earlier days...)

A lot of features used to "work" before. Were they even reliable ? This=20
is the big point IMHO ;-)

Cheers,

--=20
Pierrick Brihaye, informaticien
Service r=E9gional de l'Inventaire / DRAC Bretagne
mailto:pie...@cu... / t=E9l : +33 (0)2 99 29 67 78
http://usenet-fr.news.eu.org/fr-chartes/rfc1855.html#31. L'avez-vous lu ?