private static SuspendState SuspendImpl(ICollection <ISuspendibleRegisteredObject> allRegisteredObjects)
{
// Our behavior is:
// - We'll call each registered object's suspend method serially.
// - All methods have a combined 5 seconds to respond, at which
// point we'll forcibly return to our caller.
// - If a Resume call comes in, we'll not call any Suspend methods
// we haven't yet gotten around to, and we'll execute each
// resume callback we got.
// - Resume callbacks may fire in parallel, even if Suspend methods
// fire sequentially.
// - Resume methods fire asynchronously, so other events (such as
// Stop or a new Suspend call) could happen while a Resume callback
// is in progress.
CountdownEvent countdownEvent = new CountdownEvent(2);
SuspendState suspendState = new SuspendState(allRegisteredObjects);
// Unsafe QUWI since occurs outside the context of a request.
// We are not concerned about impersonation, identity, etc.
// Invoke any registered subscribers to let them know that we're about
// to suspend. This is done in parallel with ASP.NET's own cleanup below.
if (allRegisteredObjects.Count > 0)
{
ThreadPool.UnsafeQueueUserWorkItem(_ => {
suspendState.Suspend();
countdownEvent.Signal();
}, null);
}
else
{
countdownEvent.Signal(); // nobody is subscribed
}
// Release any unnecessary memory that we're holding on to. The GC will
// be able to reclaim these, which means that we'll have to page in less
// memory when the next request comes in.
ThreadPool.UnsafeQueueUserWorkItem(_ => {
// Release any char[] buffers we're keeping around
HttpWriter.ReleaseAllPooledBuffers();
// Trim expired entries from the runtime cache
var cache = HttpRuntime.GetCacheInternal(createIfDoesNotExist: false);
if (cache != null)
{
cache.TrimCache(0);
}
// Trim all pooled HttpApplication instances
HttpApplicationFactory.TrimApplicationInstances(removeAll: true);
countdownEvent.Signal();
}, null);
if (Debug.IsDebuggerPresent())
{
countdownEvent.Wait(); // to assist with debugging, don't time out if a debugger is attached
}
else
{
countdownEvent.Wait(_suspendMethodTimeout); // blocking call, ok for our needs since has finite wait time
}
return(suspendState);
}
