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//
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// SessionPool.h
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//
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// Library: Data
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// Package: SessionPooling
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// Module: SessionPool
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//
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// Definition of the SessionPool class.
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//
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// Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
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// and Contributors.
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//
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// SPDX-License-Identifier: BSL-1.0
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//
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#ifndef Data_SessionPool_INCLUDED
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#define Data_SessionPool_INCLUDED
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#include "Poco/Data/Data.h"
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#include "Poco/Data/PooledSessionHolder.h"
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#include "Poco/Data/PooledSessionImpl.h"
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#include "Poco/Data/Session.h"
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#include "Poco/HashMap.h"
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#include "Poco/Any.h"
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#include "Poco/Timer.h"
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#include "Poco/Mutex.h"
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#include <list>
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namespace Poco {
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namespace Data {
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class Data_API SessionPool: public RefCountedObject
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/// This class implements session pooling for POCO Data.
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///
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/// Creating a connection to a database is often a time consuming
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/// operation. Therefore it makes sense to reuse a session object
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/// once it is no longer needed.
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///
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/// A SessionPool manages a collection of SessionImpl objects
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/// (decorated with a PooledSessionImpl).
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///
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/// When a SessionImpl object is requested, the SessionPool first
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/// looks in its set of already initialized SessionImpl for an
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/// available object. If one is found, it is returned to the
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/// client and marked as "in-use". If no SessionImpl is available,
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/// the SessionPool attempts to create a new one for the client.
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/// To avoid excessive creation of SessionImpl objects, a limit
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/// can be set on the maximum number of objects.
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/// Sessions found not to be connected to the database are purged
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/// from the pool whenever one of the following events occurs:
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///
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/// - JanitorTimer event
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/// - get() request
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/// - putBack() request
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///
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/// Not connected idle sessions can not exist.
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///
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/// Usage example:
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///
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/// SessionPool pool("ODBC", "...");
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/// ...
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/// Session sess(pool.get());
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/// ...
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{
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public:
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SessionPool(const std::string& connector,
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const std::string& connectionString,
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int minSessions = 1,
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int maxSessions = 32,
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int idleTime = 60);
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/// Creates the SessionPool for sessions with the given connector
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/// and connectionString.
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///
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/// The pool allows for at most maxSessions sessions to be created.
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/// If a session has been idle for more than idleTime seconds, and more than
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/// minSessions sessions are in the pool, the session is automatically destroyed.
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~SessionPool();
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/// Destroys the SessionPool.
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Session get();
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/// Returns a Session.
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///
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/// If there are unused sessions available, one of the
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/// unused sessions is recycled. Otherwise, a new session
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/// is created.
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///
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/// If the maximum number of sessions for this pool has
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/// already been created, a SessionPoolExhaustedException
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/// is thrown.
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template <typename T>
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Session get(const std::string& name, const T& value)
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/// Returns a Session with requested property set.
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/// The property can be different from the default pool
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/// value, in which case it is reset back to the pool
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/// value when the session is reclaimed by the pool.
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{
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Session s = get();
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_addPropertyMap.insert(AddPropertyMap::value_type(s.impl(),
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std::make_pair(name, s.getProperty(name))));
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s.setProperty(name, value);
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return s;
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}
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Session get(const std::string& name, bool value);
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/// Returns a Session with requested feature set.
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/// The feature can be different from the default pool
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/// value, in which case it is reset back to the pool
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/// value when the session is reclaimed by the pool.
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int capacity() const;
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/// Returns the maximum number of sessions the SessionPool will manage.
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int used() const;
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/// Returns the number of sessions currently in use.
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int idle() const;
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/// Returns the number of idle sessions.
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int dead();
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/// Returns the number of not connected active sessions.
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int allocated() const;
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/// Returns the number of allocated sessions.
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int available() const;
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/// Returns the number of available (idle + remaining capacity) sessions.
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std::string name() const;
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/// Returns the name for this pool.
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static std::string name(const std::string& connector,
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const std::string& connectionString);
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/// Returns the name formatted from supplied arguments as "connector:///connectionString".
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void setFeature(const std::string& name, bool state);
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/// Sets feature for all the sessions.
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bool getFeature(const std::string& name);
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/// Returns the requested feature.
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void setProperty(const std::string& name, const Poco::Any& value);
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/// Sets property for all sessions.
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Poco::Any getProperty(const std::string& name);
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/// Returns the requested property.
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void shutdown();
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/// Shuts down the session pool.
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bool isActive() const;
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/// Returns true if session pool is active (not shut down).
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protected:
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virtual void customizeSession(Session& session);
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/// Can be overridden by subclass to perform custom initialization
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/// of a newly created database session.
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///
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/// The default implementation does nothing.
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typedef Poco::AutoPtr<PooledSessionHolder> PooledSessionHolderPtr;
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typedef Poco::AutoPtr<PooledSessionImpl> PooledSessionImplPtr;
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typedef std::list<PooledSessionHolderPtr> SessionList;
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typedef Poco::HashMap<std::string, bool> FeatureMap;
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typedef Poco::HashMap<std::string, Poco::Any> PropertyMap;
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void purgeDeadSessions();
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int deadImpl(SessionList& rSessions);
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void applySettings(SessionImpl* pImpl);
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void putBack(PooledSessionHolderPtr pHolder);
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void onJanitorTimer(Poco::Timer&);
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private:
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typedef std::pair<std::string, Poco::Any> PropertyPair;
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typedef std::pair<std::string, bool> FeaturePair;
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typedef std::map<SessionImpl*, PropertyPair> AddPropertyMap;
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typedef std::map<SessionImpl*, FeaturePair> AddFeatureMap;
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SessionPool(const SessionPool&);
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SessionPool& operator = (const SessionPool&);
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void closeAll(SessionList& sessionList);
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std::string _connector;
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std::string _connectionString;
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int _minSessions;
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int _maxSessions;
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int _idleTime;
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int _nSessions;
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SessionList _idleSessions;
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SessionList _activeSessions;
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Poco::Timer _janitorTimer;
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FeatureMap _featureMap;
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PropertyMap _propertyMap;
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bool _shutdown;
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AddPropertyMap _addPropertyMap;
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AddFeatureMap _addFeatureMap;
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mutable
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Poco::Mutex _mutex;
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friend class PooledSessionImpl;
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};
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inline std::string SessionPool::name(const std::string& connector,
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const std::string& connectionString)
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{
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return Session::uri(connector, connectionString);
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}
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inline std::string SessionPool::name() const
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{
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return name(_connector, _connectionString);
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}
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inline bool SessionPool::isActive() const
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{
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return !_shutdown;
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}
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} } // namespace Poco::Data
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#endif // Data_SessionPool_INCLUDED
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