Using the [ MariaDB C++ Connector ](
https://github.com/mariadb-corporation/mariadb-connector-cpp ) on ubuntu 20.04,
and gcc compiler. During load test of a webserver application it was discovered
that anytime there was more than a single concurrent connection the server
would crash. This was narrowed down to the connect member of the mariadb
driver. The errors that were being reported were always one of the following
two:
terminate called after throwing an instance of 'std::logic_error' what():
basic_string::_M_construct null not validAborted (core dumped)terminate called
after throwing an instance of 'std::invalid_argument' what(): stoiAborted
(core dumped)
As it wouldn't be feasible to post the source of the server, I have reproduced
a minimal working example that uses only standard library and
mariadb/conncpp.hpp:
```
#include <mariadb/conncpp.hpp>#include <iostream>#include <thread>#include
<string>sql::Driver* driver =
sql::mariadb::get_driver_instance();sql::SQLString connectionUrl =
"jdbc:mariadb://localhost:3306/the_database_name";sql::Properties properties =
{{"user", "the_username"}, {"password", "the_password"}};int main(){ //
simulate 2 concurrent connections each making 500 requests
std::vector<std::function<void()>> t1cbs; std::vector<std::function<void()>>
t2cbs; for(int i = 0; i < 500; i++) // if does not fail for you at 500 up
the number until it does { t1cbs.push_back([&]{
std::unique_ptr<sql::Connection> conn(driver->connect(connectionUrl,
properties)); std::cout << "t1:" << conn->getHostname().c_str() <<
std::endl; }); // comment out this block to keep the second
thread from executing, and you will see // that no errors occur
t2cbs.push_back([&]{ std::unique_ptr<sql::Connection>
conn(driver->connect(connectionUrl, properties)); std::cout << "t2:"
<< conn->getHostname().c_str() << std::endl; }); } std::thread
t1([&]{ for(auto& cb : t1cbs) cb(); }); std::thread
t2([&]{ for(auto& cb : t2cbs) cb(); }); t1.join();
t2.join(); return 0;}
```
I'm guessing the issue is on my end as I've just started working with this
particular library and have probably missed or misunderstood something.
Would someone be able to point me in the right direction as far as how I might
go about creating database connections from within separate threads?_______________________________________________
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