Am 10/24/2012 6:59 PM, schrieb Nick Sabalausky:
On Wed, 24 Oct 2012 08:23:49 +0200
Sönke Ludwig sludwig@rejectedsoftware.com wrote:Am 10/24/2012 5:01 AM, schrieb Nick Sabalausky:
To avoid the cost of establishing a new connection to a MySQL DB
on potentially every page request, I tried making one connection to
the DB upon startup of my vibe.d app and then use that one
connection for each request. Worked fine until I tried making
concurrent page requests, at which point I (perhaps unsurprisingly)
got a message about the wrong fiber accessing a connection and then
it died with an InvalidMemoryOperationError. (But annoyingly, I
can't seem to reproduce it now.)So I realize that's probably not a smart thing to do anyway, to
share a single connection across fibers. But how would I go about
reusing DB connections when possible? By using ConnectionPool,
maybe? But I'm not quite sure how to use that.In my modified version of the mysql driver there is a trivial MysqlDB
class that uses a ConnectionPool.lockConnection()returns a RAII
struct that makes sure that a single connection is not used twice.Usually I would also mirror the methods of the Connection class for
convenience, but since I don't really use it myself, I didn't put so
much time into it yet.https://github.com/rejectedsoftware/mysql-native/blob/master/source/mysql/db.d
So, if I'm understanding this right, ConnectionPool.lockConnection
creates and opens a new connection when the current fiber doesn't
already have an open connection, and returns an existing open connection
when the current fiber does have one?
It keeps a pool of connections and picks an unused one + calls acquire()
(or creates a new one if no unused connection exists). When it goes out
of scope (or better when the ref count drops to zero), it calls
release() on the connection so other fibers may call acquire().
So connections are always only temporarily pinned to a cetain fiber.