File Information
Library: Data
Package: SessionPooling
Header: Poco/Data/SessionPool.h
Description
This class implements session pooling for POCO Data.
Creating a connection to a database is often a time consuming operation. Therefore it makes sense to reuse a session object once it is no longer needed.
A SessionPool manages a collection of SessionImpl objects (decorated with a PooledSessionImpl).
When a SessionImpl object is requested, the SessionPool first looks in its set of already initialized SessionImpl for an available object. If one is found, it is returned to the client and marked as "in-use". If no SessionImpl is available, the SessionPool attempts to create a new one for the client. To avoid excessive creation of SessionImpl objects, a limit can be set on the maximum number of objects. Sessions found not to be connected to the database are purged from the pool whenever one of the following events occurs:
Not connected idle sessions can not exist.
Usage example:
SessionPool pool("ODBC", "...");
...
Session sess(pool.get());
...
Inheritance
Direct Base Classes: Poco::RefCountedObject
All Base Classes: Poco::RefCountedObject
Member Summary
Member Functions: allocated, applySettings, available, capacity, customizeSession, dead, deadImpl, get, getFeature, getProperty, idle, isActive, name, onJanitorTimer, purgeDeadSessions, putBack, setFeature, setProperty, shutdown, used
Inherited Functions: duplicate, referenceCount, release
Types
FeatureMap 
typedef Poco::HashMap < std::string, bool > FeatureMap;
PooledSessionHolderPtr
typedef Poco::AutoPtr < PooledSessionHolder > PooledSessionHolderPtr;
PooledSessionImplPtr
typedef Poco::AutoPtr < PooledSessionImpl > PooledSessionImplPtr;
PropertyMap
typedef Poco::HashMap < std::string, Poco::Any > PropertyMap;
SessionList
typedef std::list < PooledSessionHolderPtr > SessionList;
Constructors
SessionPool
SessionPool(
const std::string & connector,
const std::string & connectionString,
int minSessions = 1,
int maxSessions = 32,
int idleTime = 60
);
Creates the SessionPool for sessions with the given connector and connectionString.
The pool allows for at most maxSessions sessions to be created. If a session has been idle for more than idleTime seconds, and more than minSessions sessions are in the pool, the session is automatically destroyed.
Destructor
~SessionPool 
~SessionPool();
Destroys the SessionPool.
Member Functions
allocated
int allocated() const;
Returns the number of allocated sessions.
available
int available() const;
Returns the number of available (idle + remaining capacity) sessions.
capacity
int capacity() const;
Returns the maximum number of sessions the SessionPool will manage.
dead
int dead();
Returns the number of not connected active sessions.
get
Session get();
Returns a Session.
If there are unused sessions available, one of the unused sessions is recycled. Otherwise, a new session is created.
If the maximum number of sessions for this pool has already been created, a SessionPoolExhaustedException is thrown.
get 
template < typename T > Session get(
const std::string & name,
const T & value
);
Returns a Session with requested property set. The property can be different from the default pool value, in which case it is reset back to the pool value when the session is reclaimed by the pool.
get
Session get(
const std::string & name,
bool value
);
Returns a Session with requested feature set. The feature can be different from the default pool value, in which case it is reset back to the pool value when the session is reclaimed by the pool.
getFeature
bool getFeature(
const std::string & name
);
Returns the requested feature.
getProperty
Poco::Any getProperty(
const std::string & name
);
Returns the requested property.
idle
int idle() const;
Returns the number of idle sessions.
isActive
bool isActive() const;
Returns true if session pool is active (not shut down).
name
std::string name() const;
Returns the name for this pool.
name 
static std::string name(
const std::string & connector,
const std::string & connectionString
);
Returns the name formatted from supplied arguments as "connector:///connectionString".
setFeature
void setFeature(
const std::string & name,
bool state
);
Sets feature for all the sessions.
setProperty
void setProperty(
const std::string & name,
const Poco::Any & value
);
Sets property for all sessions.
shutdown
void shutdown();
Shuts down the session pool.
used
int used() const;
Returns the number of sessions currently in use.
applySettings
void applySettings(
SessionImpl * pImpl
);
customizeSession
virtual void customizeSession(
Session & session
);
Can be overridden by subclass to perform custom initialization of a newly created database session.
The default implementation does nothing.
deadImpl
int deadImpl(
SessionList & rSessions
);
onJanitorTimer
void onJanitorTimer(
Poco::Timer & param201
);
purgeDeadSessions
void purgeDeadSessions();
putBack
void putBack(
PooledSessionHolderPtr pHolder
);