Struct tokenbucket::TokenBucket

pub struct TokenBucket { /* private fields */ }

Represents a thread-safe token bucket object.

Implementations

impl TokenBucket

pub fn new(r: f64, b: f64) -> TokenBucket

Returns a new TokenBucket object.

Arguments

• r - The number of tokens that should be added to the bucket every second. This can also be described as the maximum rate per second that the bucket can sustain before rate limiting.

• b - The “burst” value for the bucket. This is the maximum number of tokens that can be consumed at one time when the bucket is full. It can also be desribed as the maximum volume of the bucket.

Example

let mut tb = TokenBucket::new(5.0, 100.0);

pub fn acquire(&mut self, count: f64) -> TokenAcquisitionResult

Attempts to acquire count tokens from the bucket.

Returns a TokenAcquisitionResult.

Only one acquisition call can be performed per thread at any given time. Thread safety is maintained by an internal mutex.

Every time the acquire() function is called:

1. self.r tokens will be added for every second that has elapsed since the last invocation of acquire().
2. count tokens will be removed from the bucket.
3. The tokens will never exceed the maximum burst value configured in self.b, nor will it be less than 0.

self.tokens = min { b, max { 0, tokens + rS - count } }

Arguments

• count - The number of tokens to attempt to acquire.

Example

let mut token_bucket = TokenBucket::new(5.0, 100.0);
match token_bucket.acquire(1.0) {
   Ok(rate)  => println!("acquired: rate = {}", rate),
   Err(rate) => println!("rate limited: rate = {}", rate),
};