public async ValueTask <ServerSession> GetSessionAsync(MySqlConnection connection, IOBehavior ioBehavior, CancellationToken cancellationToken) { cancellationToken.ThrowIfCancellationRequested(); // if all sessions are used, see if any have been leaked and can be recovered // check at most once per second (although this isn't enforced via a mutex so multiple threads might block // on the lock in RecoverLeakedSessions in high-concurrency situations if (m_sessionSemaphore.CurrentCount == 0 && unchecked (((uint)Environment.TickCount) - m_lastRecoveryTime) >= 1000u) { Log.Warn("{0} is empty; recovering leaked sessions", m_logArguments); RecoverLeakedSessions(); } if (ConnectionSettings.MinimumPoolSize > 0) { await CreateMinimumPooledSessions(ioBehavior, cancellationToken).ConfigureAwait(false); } // wait for an open slot (until the cancellationToken is cancelled, which is typically due to timeout) Log.Debug("{0} waiting for an available session", m_logArguments); if (ioBehavior == IOBehavior.Asynchronous) { await m_sessionSemaphore.WaitAsync(cancellationToken).ConfigureAwait(false); } else { m_sessionSemaphore.Wait(cancellationToken); } try { // check for a waiting session ServerSession session = null; lock (m_sessions) { if (m_sessions.Count > 0) { session = m_sessions.First.Value; m_sessions.RemoveFirst(); } } if (session != null) { Log.Debug("{0} found an existing session; checking it for validity", m_logArguments); bool reuseSession; if (session.PoolGeneration != m_generation) { Log.Debug("{0} discarding session due to wrong generation", m_logArguments); reuseSession = false; } else { if (ConnectionSettings.ConnectionReset) { reuseSession = await session.TryResetConnectionAsync(ConnectionSettings, ioBehavior, cancellationToken).ConfigureAwait(false); } else { reuseSession = await session.TryPingAsync(ioBehavior, cancellationToken).ConfigureAwait(false); } } if (!reuseSession) { // session is either old or cannot communicate with the server Log.Warn("{0} Session{1} is unusable; destroying it", m_logArguments[0], session.Id); AdjustHostConnectionCount(session, -1); await session.DisposeAsync(ioBehavior, cancellationToken).ConfigureAwait(false); } else { // pooled session is ready to be used; return it session.OwningConnection = new WeakReference <MySqlConnection>(connection); int leasedSessionsCountPooled; lock (m_leasedSessions) { m_leasedSessions.Add(session.Id, session); leasedSessionsCountPooled = m_leasedSessions.Count; } if (Log.IsDebugEnabled()) { Log.Debug("{0} returning pooled Session{1} to caller; m_leasedSessions.Count={2}", m_logArguments[0], session.Id, leasedSessionsCountPooled); } return(session); } } // create a new session session = new ServerSession(this, m_generation, Interlocked.Increment(ref m_lastSessionId)); if (Log.IsInfoEnabled()) { Log.Info("{0} no pooled session available; created new Session{1}", m_logArguments[0], session.Id); } await session.ConnectAsync(ConnectionSettings, m_loadBalancer, ioBehavior, cancellationToken).ConfigureAwait(false); AdjustHostConnectionCount(session, 1); session.OwningConnection = new WeakReference <MySqlConnection>(connection); int leasedSessionsCountNew; lock (m_leasedSessions) { m_leasedSessions.Add(session.Id, session); leasedSessionsCountNew = m_leasedSessions.Count; } if (Log.IsDebugEnabled()) { Log.Debug("{0} returning new Session{1} to caller; m_leasedSessions.Count={2}", m_logArguments[0], session.Id, leasedSessionsCountNew); } return(session); } catch { m_sessionSemaphore.Release(); throw; } }
public async Task <ServerSession> GetSessionAsync(MySqlConnection connection, IOBehavior ioBehavior, CancellationToken cancellationToken) { cancellationToken.ThrowIfCancellationRequested(); // if all sessions are used, see if any have been leaked and can be recovered // check at most once per second (although this isn't enforced via a mutex so multiple threads might block // on the lock in RecoverLeakedSessions in high-concurrency situations if (m_sessionSemaphore.CurrentCount == 0 && unchecked (((uint)Environment.TickCount) - m_lastRecoveryTime) >= 1000u) { RecoverLeakedSessions(); } if (m_connectionSettings.MinimumPoolSize > 0) { await CreateMinimumPooledSessions(ioBehavior, cancellationToken).ConfigureAwait(false); } // wait for an open slot (until the cancellationToken is cancelled, which is typically due to timeout) if (ioBehavior == IOBehavior.Asynchronous) { await m_sessionSemaphore.WaitAsync(cancellationToken).ConfigureAwait(false); } else { m_sessionSemaphore.Wait(cancellationToken); } try { // check for a waiting session ServerSession session = null; lock (m_sessions) { if (m_sessions.Count > 0) { session = m_sessions.First.Value; m_sessions.RemoveFirst(); } } if (session != null) { bool reuseSession; if (session.PoolGeneration != m_generation) { reuseSession = false; } else { if (m_connectionSettings.ConnectionReset) { reuseSession = await session.TryResetConnectionAsync(m_connectionSettings, ioBehavior, cancellationToken).ConfigureAwait(false); } else { reuseSession = await session.TryPingAsync(ioBehavior, cancellationToken).ConfigureAwait(false); } } if (!reuseSession) { // session is either old or cannot communicate with the server AdjustHostConnectionCount(session, -1); await session.DisposeAsync(ioBehavior, cancellationToken).ConfigureAwait(false); } else { // pooled session is ready to be used; return it session.OwningConnection = new WeakReference <MySqlConnection>(connection); lock (m_leasedSessions) m_leasedSessions.Add(session.Id, session); return(session); } } // create a new session session = new ServerSession(this, m_generation, Interlocked.Increment(ref m_lastId)); await session.ConnectAsync(m_connectionSettings, m_loadBalancer, ioBehavior, cancellationToken).ConfigureAwait(false); AdjustHostConnectionCount(session, 1); session.OwningConnection = new WeakReference <MySqlConnection>(connection); lock (m_leasedSessions) m_leasedSessions.Add(session.Id, session); return(session); } catch { m_sessionSemaphore.Release(); throw; } }