Control.Concurrent.TokenLimiter.Concurrent

Documentation

type Count = Word64

An amount of tokens

data TokenLimitConfig

A configuration for TokenLimiter

Constructors

TokenLimitConfig

Fields

• tokenLimitConfigInitialTokens :: !Count

  How many tokens should be in the bucket when it's created

• tokenLimitConfigMaxTokens :: !Count

  Maximum number of tokens the bucket can hold at any one time

• tokenLimitConfigTokensPerSecond :: !Count

  How many tokens are added to the bucket per second

Instances

Eq TokenLimitConfig

Defined in Control.Concurrent.TokenLimiter.Concurrent

Methods

(==) :: TokenLimitConfig -> TokenLimitConfig -> Bool

(/=) :: TokenLimitConfig -> TokenLimitConfig -> Bool

Show TokenLimitConfig

Defined in Control.Concurrent.TokenLimiter.Concurrent

Methods

showsPrec :: Int -> TokenLimitConfig -> ShowS

show :: TokenLimitConfig -> String

showList :: [TokenLimitConfig] -> ShowS

Generic TokenLimitConfig

Defined in Control.Concurrent.TokenLimiter.Concurrent

Associated Types

type Rep TokenLimitConfig :: Type -> Type

Methods

from :: TokenLimitConfig -> Rep TokenLimitConfig x

to :: Rep TokenLimitConfig x -> TokenLimitConfig

type Rep TokenLimitConfig

Defined in Control.Concurrent.TokenLimiter.Concurrent

type Rep TokenLimitConfig = D1 ('MetaData "TokenLimitConfig" "Control.Concurrent.TokenLimiter.Concurrent" "token-limiter-concurrent-0.0.0.0-4L9nyvrvvfa3qKmi95ra6r" 'False) (C1 ('MetaCons "TokenLimitConfig" 'PrefixI 'True) (S1 ('MetaSel ('Just "tokenLimitConfigInitialTokens") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 Count) :*: (S1 ('MetaSel ('Just "tokenLimitConfigMaxTokens") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 Count) :*: S1 ('MetaSel ('Just "tokenLimitConfigTokensPerSecond") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 Count))))

type MonotonicTime = Word64

A type synonym for a number of "monotonic time" nanoseconds.

This only exists because it is also a Word64 and would be too easy to confuse with a Count.

data TokenLimiter

A token bucket-based rate limiter

This token limiter is thread-safe and guarantees that:

• There will be no thundering herd problem
• Fairness: Waiting processes will be serviced in a first-come first-service order.

Constructors

TokenLimiter

Fields

• tokenLimiterConfig :: !TokenLimitConfig
• tokenLimiterLastServiced :: !(MVar (MonotonicTime, Count))

  The last time the limiter was used, and what the token count was at that time.

  Not that this library assumes that you never put anything into this mvar yourself and only use the functions in this library to interact with it.

Instances

Eq TokenLimiter

Defined in Control.Concurrent.TokenLimiter.Concurrent

Methods

(==) :: TokenLimiter -> TokenLimiter -> Bool

(/=) :: TokenLimiter -> TokenLimiter -> Bool

Generic TokenLimiter

Defined in Control.Concurrent.TokenLimiter.Concurrent

Associated Types

type Rep TokenLimiter :: Type -> Type

Methods

from :: TokenLimiter -> Rep TokenLimiter x

to :: Rep TokenLimiter x -> TokenLimiter

type Rep TokenLimiter

Defined in Control.Concurrent.TokenLimiter.Concurrent

type Rep TokenLimiter = D1 ('MetaData "TokenLimiter" "Control.Concurrent.TokenLimiter.Concurrent" "token-limiter-concurrent-0.0.0.0-4L9nyvrvvfa3qKmi95ra6r" 'False) (C1 ('MetaCons "TokenLimiter" 'PrefixI 'True) (S1 ('MetaSel ('Just "tokenLimiterConfig") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 TokenLimitConfig) :*: S1 ('MetaSel ('Just "tokenLimiterLastServiced") 'NoSourceUnpackedness 'SourceStrict 'DecidedStrict) (Rec0 (MVar (MonotonicTime, Count)))))

makeTokenLimiter :: TokenLimitConfig -> IO TokenLimiter

Make a token limiter

The initial number of tokens will be the minimum of the tokenLimitConfigInitialTokens and the tokenLimitConfigMaxTokens,

canDebit :: TokenLimiter -> Word64 -> IO Bool

Ask if we could debit a number of tokens, without actually doing it.

Note that this information can become stale _very_ quickly. If you want to also actually debit a number of tokens, use tryDebit instead.

tryDebit :: TokenLimiter -> Word64 -> IO Bool

Check if we can debit a number of tokens, and do it if possible.

The returned boolean represents whether the tokens were debited.

waitDebit :: TokenLimiter -> Word64 -> IO ()

Wait until the given number of tokens can be debited

Helper functions

computeCurrentCount :: TokenLimitConfig -> MonotonicTime -> Count -> MonotonicTime -> Count

Compute the current number of tokens in a bucket purely.

You should not need this function.