/// <summary>
/// Asynchronously invoke create on the given pageBlob.
/// </summary>
/// <param name="size">maximum size of the blob</param>
/// <param name="pageBlob">The page blob to create</param>
public void CreateAsync(long size, CloudPageBlob pageBlob)
{
Debug.Assert(waitingCount == 0, "Create should be called on blobs that don't already exist and exactly once");
// Asynchronously create the blob
pageBlob.BeginCreate(size, ar =>
{
try
{
pageBlob.EndCreate(ar);
}
catch (Exception e)
{
Trace.TraceError(e.Message);
}
// At this point the blob is fully created. After this line all consequent writers will write immediately. We just
// need to clear the queue of pending writers.
this.pageBlob = pageBlob;
// Take a snapshot of the current waiting count. Exactly this many actions will be cleared.
// Swapping in -1 will inform any stragglers that we are not taking their actions and prompt them to retry (and call write directly)
int waitingCountSnapshot = Interlocked.Exchange(ref waitingCount, -1);
Action <CloudPageBlob> action;
// Clear actions
for (int i = 0; i < waitingCountSnapshot; i++)
{
// inserts into the queue may lag behind the creation thread. We have to wait until that happens.
// This is so rare, that we are probably okay with a busy wait.
while (!pendingWrites.TryDequeue(out action))
{
}
action(pageBlob);
}
// Mark for deallocation for the GC
pendingWrites = null;
}, null);
}
