I just pushed a patch that should automatically manage two processes
connecting to the same environment. You typically have to coordinate
who is the master user and who is the slave so that you don't try to
recover an environment that is already in use by another process.
This causes that first process to fail, I believe, because it
discovers it's pointers into the environment are 'corrupted'.
I don't fully understand all the BDB particulars here, but I'm short
on time to fix these things. Let me know if this works for you. The
short story is that BDB is unlikely to 'just work' for a real system
using multiple processes. You have to run deadlock detection
(probably in a parallel process), you have to think about how to
coordinate processes to clean up in the event of an error, you may
have to sequence your startup, you have to think about how parallel
use of the DB effects performance. No free lunches here.
Anyway, for the details of why I added the patch see info on
DB_REGISTER option to DBENV->open (db-env-open in lisp via open-
controller in bdb-controller which is called from open-store - I've
made DB_REGISTER the default).
Berkeley DB considerations when using multiple processes:
http://www.oracle.com/technology/documentation/berkeley-db/db/api_c/env_open.html
http://www.oracle.com/technology/documentation/berkeley-db/db/ref/transapp/app.html
Some discussions of multi-processor use of BDB:
http://forums.oracle.com/forums/thread.jspa?messageID=1751065
http://forums.oracle.com/forums/thread.jspa?messageID=1436656
I'm not going to be able to track down the CL-SQL/SQLite issues
anytime soon.
Ian
On Feb 25, 2008, at 8:22 AM, Leslie P. Polzer wrote:
To isolate the problem, can you verify the base case, connect two
images to a fresh db?
For BDB:
(asdf:oos 'asdf:load-op 'elephant)
(defpackage #:ele-test (:use :cl :elephant))
(in-package :ele-test)
(defpclass myclass ()
((testslot :accessor testslot :initarg testslot :index t)))
(open-store '(:BDB "/tmp/db1") :recover t)
(setf item (make-instance 'myclass))
(setf (testslot item) 5)
I load this in two images. When I then try to access TESTSLOT in the
former, I get the mentioned error.
I'll try to make up something for the SQLite case, too.
FYI, Postmodern doesn't show any problems with my setup.
Leslie
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