private async Task CreateMinimumPooledSessions(IOBehavior ioBehavior, CancellationToken cancellationToken)
{
while (true)
{
lock (m_sessions)
{
// check if the desired minimum number of sessions have been created
if (ConnectionSettings.MaximumPoolSize - m_sessionSemaphore.CurrentCount + m_sessions.Count >= ConnectionSettings.MinimumPoolSize)
{
return;
}
}
// acquire the semaphore, to ensure that the maximum number of sessions isn't exceeded; if it can't be acquired,
// we have reached the maximum number of sessions and no more need to be created
if (ioBehavior == IOBehavior.Asynchronous)
{
if (!await m_sessionSemaphore.WaitAsync(0, cancellationToken).ConfigureAwait(false))
{
return;
}
}
else
{
if (!m_sessionSemaphore.Wait(0, cancellationToken))
{
return;
}
}
try
{
var session = new ServerSession(this, m_generation, Interlocked.Increment(ref m_lastSessionId));
Log.Info("{0} created Session{1} to reach minimum pool size", m_logArguments[0], session.Id);
await session.ConnectAsync(ConnectionSettings, m_loadBalancer, ioBehavior, cancellationToken).ConfigureAwait(false);
AdjustHostConnectionCount(session, 1);
lock (m_sessions)
m_sessions.AddFirst(session);
}
finally
{
// connection is in pool; semaphore shouldn't be held any more
m_sessionSemaphore.Release();
}
}
}
private async ValueTask <ServerSession> ConnectSessionAsync(string logMessage, int startTickCount, IOBehavior ioBehavior, CancellationToken cancellationToken)
{
var session = new ServerSession(this, m_generation, Interlocked.Increment(ref m_lastSessionId));
if (Log.IsInfoEnabled())
{
Log.Info(logMessage, m_logArguments[0], session.Id);
}
var statusInfo = await session.ConnectAsync(ConnectionSettings, startTickCount, m_loadBalancer, ioBehavior, cancellationToken).ConfigureAwait(false);
Exception?redirectionException = null;
if (statusInfo is not null && statusInfo.StartsWith("Location: mysql://", StringComparison.Ordinal))
{
// server redirection string has the format "Location: mysql://{host}:{port}/user={userId}[&ttl={ttl}]"
Log.Info("Session{0} has server redirection header {1}", session.Id, statusInfo);
if (ConnectionSettings.ServerRedirectionMode == MySqlServerRedirectionMode.Disabled)
{
Log.Info("Pool{0} server redirection is disabled; ignoring redirection", m_logArguments);
}
else if (Utility.TryParseRedirectionHeader(statusInfo, out var host, out var port, out var user))
{
if (host != ConnectionSettings.HostNames ![0] || port != ConnectionSettings.Port || user != ConnectionSettings.UserID)
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;
}
}
