Safe Haskell	None
Language	Haskell2010

Control.Concurrent.TokenLimiter

Description

Fast rate-limiting via token bucket algorithm. Uses lock-free compare-and-swap operations on the fast path when debiting tokens.

Synopsis

type Count = Int
data LimitConfig = LimitConfig {
- maxBucketTokens :: !Count
- initialBucketTokens :: !Count
- bucketRefillTokensPerSecond :: !Count
- clockAction :: IO TimeSpec
- delayAction :: TimeSpec -> IO ()
}
data RateLimiter
newRateLimiter :: LimitConfig -> IO RateLimiter
tryDebit :: LimitConfig -> RateLimiter -> Count -> IO Bool
penalize :: RateLimiter -> Count -> IO Count
waitDebit :: LimitConfig -> RateLimiter -> Count -> IO ()
defaultLimitConfig :: LimitConfig

Documentation

type Count = Int Source #

data LimitConfig Source #

Constructors

LimitConfig

Fields

maxBucketTokens :: !Count
maximum number of tokens the bucket can hold at any one time.
initialBucketTokens :: !Count
how many tokens should be in the bucket when it's created.
bucketRefillTokensPerSecond :: !Count
how many tokens should replenish the bucket per second.
clockAction :: IO TimeSpec
clock action, defaultLimitConfig uses the coarse monotonic system clock. Mostly provided for mocking in the testsuite.
delayAction :: TimeSpec -> IO ()
action to delay for the given time interval. defaultLimitConfig forwards to threadDelay. Provided for mocking.

Instances

Generic LimitConfig Source #
Instance details Defined in Control.Concurrent.TokenLimiter Associated Types type Rep LimitConfig :: Type -> Type # Methods from :: LimitConfig -> Rep LimitConfig x # to :: Rep LimitConfig x -> LimitConfig #
type Rep LimitConfig Source #
Instance details Defined in Control.Concurrent.TokenLimiter type Rep LimitConfig = D1 (MetaData "LimitConfig" "Control.Concurrent.TokenLimiter" "token-limiter-0.2.0.0-F9Jxvy0ZYWPK1TDfbudvBY" False) (C1 (MetaCons "LimitConfig" PrefixI True) ((S1 (MetaSel (Just "maxBucketTokens") SourceUnpack SourceStrict DecidedStrict) (Rec0 Count) :: S1 (MetaSel (Just "initialBucketTokens") SourceUnpack SourceStrict DecidedStrict) (Rec0 Count)) :: (S1 (MetaSel (Just "bucketRefillTokensPerSecond") SourceUnpack SourceStrict DecidedStrict) (Rec0 Count) :: (S1 (MetaSel (Just "clockAction") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 (IO TimeSpec)) :: S1 (MetaSel (Just "delayAction") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 (TimeSpec -> IO ()))))))

data RateLimiter Source #

newRateLimiter :: LimitConfig -> IO RateLimiter Source #

tryDebit :: LimitConfig -> RateLimiter -> Count -> IO Bool Source #

Attempt to pull the given number of tokens from the bucket. Returns True if the tokens were successfully debited.

penalize :: RateLimiter -> Count -> IO Count Source #

Unconditionally debit this amount of tokens from the rate limiter, driving it negative if necessary. Returns the new bucket balance.

Since: 0.2

waitDebit :: LimitConfig -> RateLimiter -> Count -> IO () Source #

Attempt to pull k tokens from the bucket, sleeping in a loop until they become available. Will not partially fulfill token requests (i.e. it loops until the entire allotment is available in one swoop), and makes no attempt at fairness or queueing (i.e. you will probably get "thundering herd" on wakeup if a number of threads are contending for fresh tokens).

defaultLimitConfig :: LimitConfig Source #