private async Task <DataTree> GetUserEntriesForDayAsync(DateTime date, string dateKey, string userId)
{
DataTree userTree = new DataTree();
DataTree result = new DataTree();
SemaphoreSlim semaphore = null;
try
{
// Lock whole cache when getting a single user entry
lock (userEntries)
{
userTree = userEntries[userId];
userTree.Create();
}
// Use semaphore instead of lock for async calls.
lock (userDataSemaphores)
{
if (userDataSemaphores.ContainsKey(userId))
{
semaphore = userDataSemaphores[userId];
}
else
{
semaphore = new SemaphoreSlim(1);
userDataSemaphores[userId] = semaphore;
}
}
// Lock the user entry when working on it.
await semaphore.WaitAsync();
// Make sure we really have a date.
string dateStr = date.Date.ToString(DateStringFormat);
// Determine if day's data is dirty and if we need to get new data.
if ((bool)userEntries[userId][dateStr]["dirty"].GetValueOrDefault(true))
{
// In case the data is dirty we need to refetch. We maintain lock to this user's data but not to anything else.
result = await RefreshUserDataForDayAsync(userTree, date, dateKey);
}
else
{
return(userEntries[userId][dateStr]);
}
}
catch (Exception ex)
{
logger.LogError("Failed to get user entries from cache.", ex);
}
finally
{
if (semaphore != null)
{
semaphore.Release();
}
}
return(result);
}
