Forgive me being a little confused; I had to get my mind back into this after some time off.
Basically, would should not open multiple store controllers in different threads onto the same database.
Onto different databases, this would be acceptable; onto the same database, you are definitely creating
the danger of inconsistent state. The code below the pattern I use.
(open-store *testbdb-spec*)
(defun test ()
(format t "store-controller ~A~%" *store-controller*)
(with-transaction (:store-controller *store-controller*)
(ele::add-to-root "x" (gensym))
(format t "Here's one try~A!~%" (ele::get-from-root "x"))
))
(sb-thread:make-thread #'test)
(dotimes (i 5) (sb-thread:make-thread #'test))
At first it might seem quite objectionably to lave the store-controller object open for a very long duration---but
I have done for days and days without a problem. So I am basically recommending one store controller. Operations
in multiple threads against one store controller should be threadsafe; I don't think this has really been tested much
but that was the plan of the original authors, I think. It is possible that the extensive changes Ian and I have made
in the last six months have messed that up.
The other problem, of course, is the potential SQLite3 problem you mention. This may keep the above
code from working on your installation (please try it for me and report the result.)
In that case, I would much rather address the SQLite3-specific problem than workaround things in
a very complicated way.
I could not open the url to trouble ticket that you posted.
If it is a question of a compilation switch in SQLite3, is that an option for you? Could you recompile
it in your environment?
n Wed, 2006-04-19 at 18:34 +0300, Ignas Mik
Hi, I am trying to use elephant as a backend data store for my
blogging application. And have encountered some problems with it ...
As i want to only commit the transaction in cases of error and tbnl is
using throw for redirects i need to manualy open/close transactions,
but it seems (ele:start-transaction) is only designed to work with BDB
backend, so i must use (clsql:start-transaction) instead.
At the moment the wrapper around each request looks like this:
(defun common-blog-view-wrapper (function)
(ele:with-open-store (`(:sqlite3 ,(format nil "~A"
(get-config-option "database-path"))))
(let ((error nil)
(transaction nil))
(unwind-protect
(handler-bind ((error (lambda (cond)
(declare (ignore cond))
(setf error t))))
(clsql:start-transaction)
(setf transaction t)
(tbnl::string-to-octets (funcall function) :utf-8))
(when transaction
(if error
(clsql:rollback)
(clsql:commit)))))))
As sqlite requires each thread to have it's own connection by throwing
an error if one thread tries to reuse a connection created by another
thread at least on Ubuntu Dapper. Google says that it depends on a
compile time flag for libsqlite3. Everything works more or less fine ,
but when i am reloading the page multiple times in a row very fast i
am getting a traceback (attached). And can't quite grok what went
wrong ... Maybe some one who knows internals of elephant can help me
out with this, as i could not really track where could a database
connection appear in another thread.
A testcase for SBCL:
(defun test ()
(ele:with-open-store ('(:sqlite3 "/home/ignas/src/common-blog/dev.db"))))
(sb-thread:make-thread #'test) ;; a few times - works
(dotimes (i 3) (sb-thread:make-thread #'test)) ;; you get 3 tracebacks
By the way thanks for a wonderful library!
--
Ignas Mikalajūnas
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