How a datasource pools its connections. More...

#include <libcmdbm.h>

Data Fields
uint32_t	pingterm
	Seconds between two rounds of the idle connection check.

CMBool	pingtest
	Whether idle connections are checked every `pingterm` seconds.

CMBool	testonborrow
	Whether a connection is validated when it is borrowed.

uint32_t	initcnt
	Connections opened when the datasource starts up.

uint32_t	maxcnt
	Upper limit of open connections. A session which asks for one beyond it waits, and gives up after five seconds.

char *	testsql
	The statement which validates a connection.

Detailed Description

How a datasource pools its connections.

The struct is copied by CMDBM_DatabaseCreate, so a caller may fill one in on the stack, and testsql is copied too.

Field Documentation

◆ pingterm

uint32_t CMDBM_PoolConfig::pingterm

Seconds between two rounds of the idle connection check.

0 is taken as the default of 30 - the check is a repeating task and cannot run with no period at all.

◆ pingtest

CMBool CMDBM_PoolConfig::pingtest

Whether idle connections are checked every pingterm seconds.

The check runs testsql on each connection currently sitting in the pool, and replaces the ones which do not answer - which is what keeps a pool usable across a database restart or an idle timeout on the server.

◆ testonborrow

CMBool CMDBM_PoolConfig::testonborrow

Whether a connection is validated when it is borrowed.

The safe setting, and the default: a session never gets a connection the database has dropped meanwhile. It costs one round trip per checkout, which is what pingtest alone avoids.

With this and pingtest both off, connections are handed out without ever being tested.

◆ testsql

char* CMDBM_PoolConfig::testsql

The statement which validates a connection.

NULL takes the one of the module, CMDBM_ModuleInterface::GetTestQuery - which is how an Oracle datasource ends up validating with "select 1 from dual" without anything having to say so.

The documentation for this struct was generated from the following file: