private void AcceptSession(CancellationToken cancellationToken)
{
dynamicThrottling.WaitUntilAllowedParallelism(cancellationToken);
if (!cancellationToken.IsCancellationRequested)
{
// Initialize a custom action acting as a callback whenever a non-transient exception occurs while accepting a session.
Action <Exception> recoverAcceptSession = ex => {
// Just log an exception. Do not allow an unhandled exception to terminate the message receive loop abnormally.
Trace.TraceError("An unrecoverable error occurred while trying to accept a session in subscription {1}:\r\n{0}", ex, subscription);
dynamicThrottling.Penalize();
if (!cancellationToken.IsCancellationRequested)
{
// Continue accepting new sessions until told to stop regardless of any exceptions.
TaskEx.Delay(10000).ContinueWith(t => AcceptSession(cancellationToken));
}
};
receiveRetryPolicy.ExecuteAction(
cb => client.BeginAcceptMessageSession(AcceptSessionLongPollingTimeout, cb, null),
ar => {
// Complete the asynchronous operation. This may throw an exception that will be handled internally by retry policy.
try {
return(client.EndAcceptMessageSession(ar));
} catch (TimeoutException) {
// TimeoutException is not just transient but completely expected in this case, so not relying on Topaz to retry
return(null);
}
},
session => {
if (session != null)
{
instrumentation.SessionStarted();
dynamicThrottling.NotifyWorkStarted();
// starts a new task to process new sessions in parallel when enough threads are available
Task.Factory.StartNew(() => AcceptSession(cancellationToken), cancellationToken);
ReceiveMessagesAndCloseSession(session, cancellationToken);
}
else
{
AcceptSession(cancellationToken);
}
},
recoverAcceptSession);
}
}