Hello,
(sorry if the question was already asked, but searching the term
"engine" in the archives was complicated with the name pollution caused
by the sf.net sponsors....)
In short: I'm developing a web based application (written in zope3)
which needs to use different database credentials depending on
the application credentials which may obviosly vary between requests
even for the same thead.
(because I have an existing security framework on the sql server and
triggers that logs the username that modifies rows etc)
I wouldn't like to recreate a new engine, associated tables and
mappers for every new request. I see some possible paths:
1) managing a pool of engines,mappers and tables kept in a dictionary
mapped by application user. (subsuboptimal solution)
2) creating a wrapper for engine that proxies itself to the correct
engine appropriated for the current request. However
I'm not sure whether the engine object is traversed for each
access to the connection or some attributes of the connection are
saved inside
table,mapper etc objects
3) somehow hooking the db connection pool used by the underlining
engine in such a way that
it transparenty chooses the dbapi connection appropriate for the
application credential currently processed by the thread.
I see that the SingletonThreadPool.do_get() method access a
dictionary ("_conns"). Perhaps it would be possible to put a specific
connection
there before each request processing but I don't like fiddling with
"private" attributes.
Also changing the underlining connection/engine may intefere with the
objectstore? What should I do before and after a request processing
(assuming request doesn't span connection boundaries) in order to
insure consistency without too much overhead?
is there a preferred way to doing this?
marko
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