Xapian discuss - Mar 2010 - xapian-tcpsrv php in real fastcgi loop

Hello,

i'm fresh new to xapian (and impressed.. fast, faster, xapian). And so i
have
a problem with no solution at the moment.

I have a webapp based on php5 in a special fastcgi loop environment (thus 
there are some loops spawned handling multiple requests so there is no need 
for php to recreate classes and Objects all the time).

I implemented a xapian wrapper class to access a remote database provided by 
xapian-tcpsrv using this command:

xapian-tcpsrv --port 5050 --writable /var/lib/xapian/objects/

I indexed all ths stuff we need and tested the search. Fast and furious, but i 
randomly get:

REMOTE:Unable to acquire database write lock on /var/lib/xapian/objects/: 
already locked

First, this is a connection tried to open with Xapian::remote_open. So i think 
it should'nt create a write lock. Otherwise, i started xapian-tcpsrv with --
writable, do i have to start to instances on the same directory, one writable 
and one not?

Second, if i understand the examples right i have to unset the database object 
to get the lock released. But i don't want to close the connection. I Just 
want to release the lock if possible. Is there any convenient way to let any 
lock go if everything is done in a process?

Third, if there is a lock why is there a exception thrown? Wouldn't it be 
better to wait for the lock a well defined time similar to database locks for 
example?

I think i do something (or some things) wrong here, but i don't know what it
is.

Any help greatly appreciated

Greetings so far
DonMartio

Hello again,

i've gone a little bit further by reseting the database objects every loop.
But i still got randomly lock exceptions and netstat gives me connections in 
CLOSE_WAIT forever. After lighty restart they are gone.

Is there any way to force a close on the connection?

Greetings again
DonMartio



Am Freitag, 19. M?rz 2010 19:25:35 schrieb Martin
Regner:
> Hello,
> 
> i'm fresh new to xapian (and impressed.. fast, faster, xapian). And so
i
> have a problem with no solution at the moment.
> 
> I have a webapp based on php5 in a special fastcgi loop environment (thus
> there are some loops spawned handling multiple requests so there is no need
> for php to recreate classes and Objects all the time).
> 
> I implemented a xapian wrapper class to access a remote database provided
> by xapian-tcpsrv using this command:
> 
> xapian-tcpsrv --port 5050 --writable /var/lib/xapian/objects/
> 
> I indexed all ths stuff we need and tested the search. Fast and furious,
> but i randomly get:
> 
> REMOTE:Unable to acquire database write lock on /var/lib/xapian/objects/:
> already locked
> 
> First, this is a connection tried to open with Xapian::remote_open. So i
> think it should'nt create a write lock. Otherwise, i started
xapian-tcpsrv
> with -- writable, do i have to start to instances on the same directory,
> one writable and one not?
> 
> Second, if i understand the examples right i have to unset the database
> object to get the lock released. But i don't want to close the
connection.
> I Just want to release the lock if possible. Is there any convenient way
> to let any lock go if everything is done in a process?
> 
> Third, if there is a lock why is there a exception thrown? Wouldn't it
be
> better to wait for the lock a well defined time similar to database locks
> for example?
> 
> I think i do something (or some things) wrong here, but i don't know
what
> it is.
> 
> Any help greatly appreciated
> 
> Greetings so far
> DonMartio
> 
> 
> _______________________________________________
> Xapian-discuss mailing list
> Xapian-discuss at lists.xapian.org
> http://lists.xapian.org/mailman/listinfo/xapian-discuss

On Fri, Mar 19, 2010 at 07:25:35PM +0100, Martin Regner
wrote:
> First, this is a connection tried to open with Xapian::remote_open. So i
> think it should'nt create a write lock. Otherwise, i started
xapian-tcpsrv
> with -- writable, do i have to start to instances on the same directory,
one
> writable and one not?
Yes, you do for Xapian 1.0.x.

Xapian 1.1.0 fixed this:

http://trac.xapian.org/ticket/145
> Second, if i understand the examples right i have to unset the database
> object to get the lock released. But i don't want to close the
connection. I
> Just want to release the lock if possible. Is there any convenient way to
let
> any lock go if everything is done in a process?
Again, not in 1.0.x.  It can be a problem as it is quite easy to inadvertently
keep a reference to the database (either through another Xapian object, or
with some scripting languages because there's a garbage collection phase
which
needs to run before the C++ destructor actually gets called).

1.1.0 added a Database::close() method to close a database right away, and
release any lock and close any network connections.
> Third, if there is a lock why is there a exception thrown? Wouldn't it
be
> better to wait for the lock a well defined time similar to database locks
for
> example?
Sometimes you don't want to wait, but it would be useful to be able to
specify
that you want the attempt to block until it can get a write lock.  There's
already an open ticket for this:

http://trac.xapian.org/ticket/275

Cheers,
    Olly