public RateLimitCacheManager(
IRateLimitCache rateLimitCache,
IRateLimitHelper rateLimitHelper)
{
_rateLimitCache = rateLimitCache;
_rateLimitHelper = rateLimitHelper;
}
/// <summary>
/// Tells if threshold is crossed now with current state of cache
///
/// Following ideas are important for this algorithm:
/// 1. Keep a circular queue (array) of request counts on indexes, where index represents
/// a time in the slot span window. The same queue will be overlapped for future requests,
/// size of the queue represents the time slot and the slot window can be begninning or ending
/// at any index.
/// 2. Time always moves forward
/// Beginning of slot (i.e. past) will always be behind the slot ending (i.e. present)
/// </summary>
/// <param name="cache">
/// cache.RequestCounts: Keeps request counts of calls in curentwindow
/// cache.TotalRequestsInSlotSpan: Keeps track of total number of request counts in current window,
/// current window is based on Now and Present Index
/// </param>
/// <returns></returns>
public static bool IsThresholdCrossed(uint now, IRateLimitCache cache)
{
// present index in circular queue "RequestCounts"
ushort presentIndex = Convert.ToUInt16(now % cache.SlotSpanInSeconds);
if (now < cache.TimeOfLastApiCall)
{
// now is older than the time when last api was received.
throw new InvalidOperationException($"Time Machine usage is not allowed.");
}
var secondsSinceLastRequest = now - cache.TimeOfLastApiCall;
// If it's been more than slot span, then clear the stale values
if (secondsSinceLastRequest > cache.SlotSpanInSeconds)
{
// following properties become obsololete, out of the slot window, so reset
cache.TotalRequestsInSlotSpan = 0;
cache.RequestCounts.Initialize();
cache.PastIndex = 0;
}
// Fact: Time always moves forward and
// Past is always behind present
if (cache.PastIndex > presentIndex)
{
// If present is behind past, it's an overlap
// i.e. the request count value on present index is from past cycle,
// which means, it is not part of the current slot window
// Also it was part of TotalRequestsInSlotSpan, which is not anymore.
cache.TotalRequestsInSlotSpan -= cache.RequestCounts[presentIndex];
// make this request as first request on presentIndex, a new slot window is entered.
cache.RequestCounts[presentIndex] = 1;
}
// Add a successful request in TotalRequestsInSlotSpan
++cache.TotalRequestsInSlotSpan;
// present will become past
cache.PastIndex = presentIndex;
cache.TimeOfLastApiCall = now;
if (cache.TotalRequestsInSlotSpan > cache.MaxRequestsInSlotSpan)
{
// As it was not a successful request, remove it from TotalRequestsInSlotSpan
--cache.TotalRequestsInSlotSpan;
// Update LastTimeWhenThresholdCrossed, so that all APIs will be blocked for next timeToBlock seconds
cache.LastTimeWhenThresholdCrossed = now;
return(true);
}
// Add a successful request at present index in RequestCounts
++cache.RequestCounts[presentIndex];
return(false);
}
static RateLimit()
{
Initialize();
_rateLimitAwaiter = TweetinviContainer.Resolve<IRateLimitAwaiter>();
_rateLimitCacheManager = TweetinviContainer.Resolve<IRateLimitCacheManager>();
_rateLimitCache = TweetinviContainer.Resolve<IRateLimitCache>();
}
static RateLimit()
{
Initialize();
_rateLimitAwaiter = TweetinviContainer.Resolve <IRateLimitAwaiter>();
_rateLimitCacheManager = TweetinviContainer.Resolve <IRateLimitCacheManager>();
_rateLimitCache = TweetinviContainer.Resolve <IRateLimitCache>();
}
public RateLimitCacheManager(
ICredentialsAccessor credentialsAccessor,
ITwitterRequester twitterRequester,
IHelpQueryGenerator helpQueryGenerator,
IJsonObjectConverter jsonObjectConverter,
IRateLimitCache rateLimitCache,
IRateLimitHelper rateLimitHelper,
ITwitterQueryFactory twitterQueryFactory)
{
_credentialsAccessor = credentialsAccessor;
_twitterRequester = twitterRequester;
_helpQueryGenerator = helpQueryGenerator;
_jsonObjectConverter = jsonObjectConverter;
_rateLimitCache = rateLimitCache;
_rateLimitHelper = rateLimitHelper;
_twitterQueryFactory = twitterQueryFactory;
}
public RateLimitCacheManager(
ICredentialsAccessor credentialsAccessor,
ITwitterRequester twitterRequester,
IHelpQueryGenerator helpQueryGenerator,
IJsonObjectConverter jsonObjectConverter,
IRateLimitCache rateLimitCache,
IRateLimitHelper rateLimitHelper,
ITwitterQueryFactory twitterQueryFactory)
{
_credentialsAccessor = credentialsAccessor;
_twitterRequester = twitterRequester;
_helpQueryGenerator = helpQueryGenerator;
_jsonObjectConverter = jsonObjectConverter;
_rateLimitCache = rateLimitCache;
_rateLimitHelper = rateLimitHelper;
_twitterQueryFactory = twitterQueryFactory;
}
public bool IsLimitedApi(IRateLimitCache cache, Object lockMe)
{
// get now without milliseconds
var now = UnixEpoch.Now;
lock (lockMe)
{
if (ShouldBeKeptBlockedFor(now, cache))
{
return(true);
}
// This will be executed only after timeToBlock seconds of last time threshold crossed.
if (IsThresholdCrossed(now, cache))
{
return(true);
}
}
// Don't limit the API call
return(false);
}
public static bool ShouldBeKeptBlockedFor(uint now, IRateLimitCache cache)
{
var timSpanSinceThreshHoldCrossedLastTime = now - cache.LastTimeWhenThresholdCrossed;
return(timSpanSinceThreshHoldCrossedLastTime <= cache.TimeSpanToKeepBlockedInSeconds);
}
public RateLimitService(IConfiguration configuration)
{
_rateLimitCacheForCityApi = new RateLimitCacheForCityApi(configuration);
_rateLimitCacheForRoomApi = new RateLimitCacheForRoomApi(configuration);
}
