public DoubleBufferCache(int capacity = 2000, double evictionTimeSec = 20)
{
_capacity = capacity;
// we set swap interval to half evict time, as stale items stay in cache for time which
// is double of swap interval - first item sits in recent items, then in older items
_swapInterval = TimeSpan.FromSeconds(evictionTimeSec / 2);
_recentItems = new Dictionary <TKey, TValue>(capacity + 10);
_olderItems = new Dictionary <TKey, TValue>(capacity + 10);
// create initial metrics and make a buffer swap to finish full initialization
_metrics = new CacheMetrics()
{
StartedOn = AppTime.UtcNow
};
SwapBuffers();
}
private void SwapBuffers()
{
var utcNow = AppTime.UtcNow;
//swap metrics
_metrics.ItemCount = Math.Max(_recentItems.Count, _olderItems.Count);
_metrics.EndedOn = utcNow;
_oldMetrics = _metrics;
_metrics = new CacheMetrics()
{
StartedOn = utcNow
};
//swap buffers
var temp = _olderItems;
_olderItems = _recentItems;
_recentItems = temp;
_recentItems.Clear();
// update times
_lastSwappedOn = utcNow;
_nextSwapOn = utcNow.Add(_swapInterval);
}
