public CollapsedRequest <RequestResponseType, RequestArgumentType> SubmitRequest(RequestArgumentType arg, CancellationToken token)
{
/*
* We only want the timer ticking if there are actually things to do so we register it the first time something is added.
*/
if (!timerListenerRegistered.Value && timerListenerRegistered.CompareAndSet(false, true))
{
/* schedule the collapsing task to be executed every x milliseconds (x defined inside CollapsedTask) */
timerListenerReference.Value = timer.AddListener(new CollapsedTask <BatchReturnType, RequestResponseType, RequestArgumentType>(this));
}
// loop until succeed (compare-and-set spin-loop)
while (true)
{
RequestBatch <BatchReturnType, RequestResponseType, RequestArgumentType> b = batch.Value;
if (b == null)
{
throw new InvalidOperationException("Submitting requests after collapser is shutdown");
}
CollapsedRequest <RequestResponseType, RequestArgumentType> response = b.Offer(arg, token);
// it will always get an CollapsedRequest unless we hit the max batch size
if (response != null)
{
return(response);
}
else
{
// this batch can't accept requests so create a new one and set it if another thread doesn't beat us
CreateNewBatchAndExecutePreviousIfNeeded(b);
}
}
}
/**
* Best-effort attempt to remove an argument from a batch. This may get invoked when a cancellation occurs somewhere downstream.
* This method finds the argument in the batch, and removes it.
*
*/
internal void Remove(RequestArgumentType arg)
{
if (batchStarted.Value)
{
//nothing we can do
return;
}
if (batchLock.TryEnterReadLock(1))
{
try
{
/* double-check now that we have the lock - if the batch is started, deleting is useless */
if (batchStarted.Value)
{
return;
}
CollapsedRequest <RequestResponseType, RequestArgumentType> existing = null;
if (arg == null)
{
nullArg.Value = null;
}
if (argumentMap.TryRemove(arg, out existing))
{
// Log
}
}
finally
{
batchLock.ExitReadLock();
}
}
}
public CollapsedRequest <RequestResponseType, RequestArgumentType> Offer(RequestArgumentType arg, CancellationToken token)
{
/* short-cut - if the batch is started we reject the offer */
if (batchStarted.Value)
{
return(null);
}
/*
* The 'read' just means non-exclusive even though we are writing.
*/
if (batchLock.TryEnterReadLock(1))
{
try
{
/* double-check now that we have the lock - if the batch is started we reject the offer */
if (batchStarted.Value)
{
return(null);
}
if (argumentMap.Count >= maxBatchSize)
{
return(null);
}
else
{
CollapsedRequest <RequestResponseType, RequestArgumentType> collapsedRequest = new CollapsedRequest <RequestResponseType, RequestArgumentType>(arg, token);
TaskCompletionSource <RequestResponseType> tcs = new TaskCompletionSource <RequestResponseType>(collapsedRequest);
collapsedRequest.CompletionSource = tcs;
CollapsedRequest <RequestResponseType, RequestArgumentType> existing = null;
if (arg == null)
{
existing = GetOrAddNullArg(collapsedRequest);
}
else
{
existing = argumentMap.GetOrAdd(arg, collapsedRequest);
}
/*
* If the argument already exists in the batch, then there are 2 options:
* A) If request caching is ON (the default): only keep 1 argument in the batch and let all responses
* be hooked up to that argument
* B) If request caching is OFF: return an error to all duplicate argument requests
*
* This maintains the invariant that each batch has no duplicate arguments. This prevents the impossible
* logic (in a user-provided mapResponseToRequests for HystrixCollapser and the internals of HystrixObservableCollapser)
* of trying to figure out which argument of a set of duplicates should get attached to a response.
*
* See https://github.com/Netflix/Hystrix/pull/1176 for further discussion.
*/
if (existing != collapsedRequest)
{
bool requestCachingEnabled = properties.RequestCacheEnabled;
if (requestCachingEnabled)
{
return(existing);
}
else
{
throw new ArgumentException("Duplicate argument in collapser batch : [" + arg + "] This is not supported. Please turn request-caching on for HystrixCollapser:" + commandCollapser.CollapserKey.Name + " or prevent duplicates from making it into the batch!");
}
}
else
{
return(collapsedRequest);
}
}
}
finally
{
batchLock.ExitReadLock();
}
}
else
{
return(null);
}
}
internal CollapsedRequest <RequestResponseType, RequestArgumentType> GetOrAddNullArg(CollapsedRequest <RequestResponseType, RequestArgumentType> collapsedRequest)
{
if (nullArg.CompareAndSet(null, collapsedRequest))
{
return(collapsedRequest);
}
return(nullArg.Value);
}