Xapian discuss - Apr 2007 - Flint Database 'Can't acquire write lock'?

Hi,

 I'm using xapian-core-0.9.9, built on a 64bit linux machine
(Linux 2.4.21-143-smp x86_64 unknown ), employing a bash shell.  I
have successfully built several quartz databases of various sizes, and
am trying to construct a flint database now, using the same code.  As
per the readme page
( http://wiki.xapian.org/FlintBackend_2fHowToCreateAFlintDatabase )
I tried:
$ export XAPIAN_PREFER_FLINT=True

however this then resulted in a 'Exception: Unable to acquire database
write lock on test'
message.  If I then
$ unset XAPIAN_PREFER_FLINT

and rerun my program it builds the database without complaint.

I was able to duplicate this sequence of events using the unchanged
simpleindex program that can be found in the examples subdirectory of
xapian-core-0.9.9. I started without specifying the
XAPIAN_PREFER_FLINT environment variable, meaning (I think) that the
resulting database should be built according to the quartz
specification.

First I created a simple test file, containing 3 entries, to index:
--begin doc---
this is a test

this is another test

this is a third and final test
--end doc--

I think ran the following command:
$  cat test.txt | ./simpleindex testdb

and searched the resulting db:
$ ./simplesearch testdb/ test
Performing query `Xapian::Query(test)'
3 results found
ID 1 99% [this is a test]
ID 2 99% [this is another test]
ID 3 86% [this is a third and final test]

Everything worked fine.  I then exported the XAPIAN_PREFER_FLINT variable:
$ export XAPIAN_PREFER_FLINT=True

and attempted to rebuild the database after first deleting it:
$ rm -rf testdb/
$ cat test.txt | ./simpleindex testdb
Exception: Unable to acquire database write lock on testdb

It didn't work, and I don't know why... I thought perhaps it was
because I hadn't explicitly enabled flint during the configuration and
build process (it is enabled by default though), so reran configure
and recompiled with the --enable-backend-flint option set, but it was
all to no avail.  Any suggestions about what might be the root of this
problem  will be greatly appreciated.  Perhaps I am just missing
something really simple.

Thanks,

Joe

On Fri, Apr 20, 2007 at 06:37:47PM +0900, Josef Novak
wrote:
> I'm using xapian-core-0.9.9, built on a 64bit linux machine
> (Linux 2.4.21-143-smp x86_64 unknown ), employing a bash shell.
Flint relies on fcntl() for locking, so perhaps the filing system
you have the database on doesn't support this.  What is the filing
system?  If it's NFS, make sure you're running 'lockd'.

Quartz uses completely different locking technique which works on
NFS without lockd, but it leaves a stale lock behind if the process
exits unexpectedly, which is annoying.

If it's not obviously the FS, can you try a snapshot tarball of SVN
HEAD?  There are have been some minor tweaks to the locking code:

http://www.oligarchy.co.uk/xapian/trunk/

Cheers,
    Olly