public static string GetFriendlyTimeoutErrorMessage(TaskCanceledException ex, bool isFinalAttempt, bool ignoreFailure)
{
// "A task was canceled" doesn't make sense to users, use a better error message.
var reaction = "Retrying";
if (isFinalAttempt && ignoreFailure)
{
reaction = "Ignoring the remote source";
}
else if (isFinalAttempt)
{
reaction = "Exiting";
}
return $"HTTP request timed out. {reaction}.";
}
/// <summary>
/// Returns a list of exceptions by aggregating the holder's contents. Or null if
/// no exceptions have been thrown.
/// </summary>
/// <param name="includeTaskCanceledExceptions">Whether to include a TCE if cancelled.</param>
/// <returns>An aggregate exception, or null if no exceptions have been caught.</returns>
private AggregateException GetExceptions(bool includeTaskCanceledExceptions)
{
//
// WARNING: The Task/Task<TResult>/TaskCompletionSource classes
// have all been carefully crafted to insure that GetExceptions()
// is never called while AddException() is being called. There
// are locks taken on m_contingentProperties in several places:
//
// -- Task<TResult>.TrySetException(): The lock allows the
// task to be set to Faulted state, and all exceptions to
// be recorded, in one atomic action.
//
// -- Task.Exception_get(): The lock ensures that Task<TResult>.TrySetException()
// is allowed to complete its operation before Task.Exception_get()
// can access GetExceptions().
//
// -- Task.ThrowIfExceptional(): The lock insures that Wait() will
// not attempt to call GetExceptions() while Task<TResult>.TrySetException()
// is in the process of calling AddException().
//
// For "regular" tasks, we effectively keep AddException() and GetException()
// from being called concurrently by the way that the state flows. Until
// a Task is marked Faulted, Task.Exception_get() returns null. And
// a Task is not marked Faulted until it and all of its children have
// completed, which means that all exceptions have been recorded.
//
// It might be a lot easier to follow all of this if we just required
// that all calls to GetExceptions() and AddExceptions() were made
// under a lock on m_contingentProperties. But that would also
// increase our lock occupancy time and the frequency with which we
// would need to take the lock.
//
// If you add a call to GetExceptions() anywhere in the code,
// please continue to maintain the invariant that it can't be
// called when AddException() is being called.
//
// We'll lazily create a TCE if the task has been canceled.
Exception canceledException = null;
if (includeTaskCanceledExceptions && IsCanceled)
{
// Backcompat:
// Ideally we'd just use the cached OCE from this.GetCancellationExceptionDispatchInfo()
// here. However, that would result in a potentially breaking change from .NET 4, which
// has the code here that throws a new exception instead of the original, and the EDI
// may not contain a TCE, but an OCE or any OCE-derived type, which would mean we'd be
// propagating an exception of a different type.
canceledException = new TaskCanceledException(this);
}
var exceptionsHolder = ThreadingHelper.VolatileRead(ref _exceptionsHolder);
if (exceptionsHolder != null && exceptionsHolder.ContainsFaultList)
{
// No need to lock around this, as other logic prevents the consumption of exceptions
// before they have been completely processed.
return(_exceptionsHolder.CreateExceptionObject(false, canceledException));
}
if (canceledException != null)
{
// No exceptions, but there was a cancelation. Aggregate and return it.
return(new AggregateException(canceledException));
}
return(null);
}
/// <summary>
/// Returns a list of exceptions by aggregating the holder's contents. Or null if
/// no exceptions have been thrown.
/// </summary>
/// <param name="includeTaskCanceledExceptions">Whether to include a TCE if cancelled.</param>
/// <returns>An aggregate exception, or null if no exceptions have been caught.</returns>
private AggregateException GetExceptions(bool includeTaskCanceledExceptions)
{
//
// WARNING: The Task/Task<TResult>/TaskCompletionSource classes
// have all been carefully crafted to insure that GetExceptions()
// is never called while AddException() is being called. There
// are locks taken on m_contingentProperties in several places:
//
// -- Task<TResult>.TrySetException(): The lock allows the
// task to be set to Faulted state, and all exceptions to
// be recorded, in one atomic action.
//
// -- Task.Exception_get(): The lock ensures that Task<TResult>.TrySetException()
// is allowed to complete its operation before Task.Exception_get()
// can access GetExceptions().
//
// -- Task.ThrowIfExceptional(): The lock insures that Wait() will
// not attempt to call GetExceptions() while Task<TResult>.TrySetException()
// is in the process of calling AddException().
//
// For "regular" tasks, we effectively keep AddException() and GetException()
// from being called concurrently by the way that the state flows. Until
// a Task is marked Faulted, Task.Exception_get() returns null. And
// a Task is not marked Faulted until it and all of its children have
// completed, which means that all exceptions have been recorded.
//
// It might be a lot easier to follow all of this if we just required
// that all calls to GetExceptions() and AddExceptions() were made
// under a lock on m_contingentProperties. But that would also
// increase our lock occupancy time and the frequency with which we
// would need to take the lock.
//
// If you add a call to GetExceptions() anywhere in the code,
// please continue to maintain the invariant that it can't be
// called when AddException() is being called.
//
// We'll lazily create a TCE if the task has been canceled.
Exception canceledException = null;
if (includeTaskCanceledExceptions && IsCanceled)
{
// Backcompat:
// Ideally we'd just use the cached OCE from this.GetCancellationExceptionDispatchInfo()
// here. However, that would result in a potentially breaking change from .NET 4, which
// has the code here that throws a new exception instead of the original, and the EDI
// may not contain a TCE, but an OCE or any OCE-derived type, which would mean we'd be
// propagating an exception of a different type.
canceledException = new TaskCanceledException(this);
}
var exceptionsHolder = ThreadingHelper.VolatileRead(ref _exceptionsHolder);
if (exceptionsHolder != null && exceptionsHolder.ContainsFaultList)
{
// No need to lock around this, as other logic prevents the consumption of exceptions
// before they have been completely processed.
return _exceptionsHolder.CreateExceptionObject(false, canceledException);
}
if (canceledException != null)
{
// No exceptions, but there was a cancelation. Aggregate and return it.
return new AggregateException(canceledException);
}
return null;
}
