[odb-users] safe usage odb connection pool in multi threaded
environment (odb 2.4.0)
pustovalovdmit at gmail.com
Fri Apr 28 04:23:13 EDT 2017
I want to figure out a proper way to manage database connection pool
assuming I want to use connection in different threads.
As far as I understand I should do it like this:
static constexpr auto max_connections = 20;
// 1) create connection pool
auto pool = std::make_unique<odb::mysql::connection_pool_factory>(max_connections);
// 2) bind it to database passing connection pool to odb::database constructor
auto db = std::make_unique<odb::mysql::database>(user, password,
db_name, host, 0, nullptr, "utf8", 0, std::move(pool));
// 3) get available connection_ptr from pool
auto conn = db->connection();
// 4) use connection_ptr (possibly on other thread)
auto& db = conn1->database();
Is there a right way to accomplish my goal?
I have few doubts in correctness and safety of code in lambda passed to thread:
1) When I pass transaction_impl (result of odb::connection::begin) to
odb::transaction constructor does queries work on that connection not
on some default odb::database connection
2) If I work directly with odb::connection assigned to connection pool
does all queries work on one single default (first created?)
connection from this pool.
3) Is it safe to use odb::database object concurrently without mutex
protection if I get reference to it from connection (from
odb::connection::database function). I mean I need odb::database
interface in different threads, plain query interface of
odb::conenction is not enough.
Thanks in advance!
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