Package dev.relism.flash.ext.limiter.strategy

Class TokenBucketStrategy

java.lang.Object

dev.relism.flash.ext.limiter.strategy.TokenBucketStrategy

All Implemented Interfaces:

RateLimitStrategy

public final class TokenBucketStrategy
extends Object
implements RateLimitStrategy

Token-bucket rate limit: tokens refill continuously at a rate of limit / windowMs tokens per millisecond, up to a maximum of limit tokens. Each request consumes one token. Burst traffic is absorbed until the bucket empties.

Implementation

• Bucket.slot0 — current token count scaled by 1000L (allows sub-token precision without floating-point). Starts at 0; treated as maxScaled when Bucket.slot1 is 0 (first call → bucket starts full).
• Bucket.slot1 — last-refill timestamp in ms. 0 = not yet initialised.

Each request CAS-loops on slot0; slot1 is advanced monotonically via CAS after a successful token consumption — never regresses to an older timestamp under concurrent load.

Constructor Summary

Constructors

Constructor	Description
TokenBucketStrategy()

Method Summary

Modifier and Type	Method	Description
boolean	check(Bucket bucket, LimitConfig cfg, long[] out)	Checks whether this request is within the limit and updates the bucket atomically.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

TokenBucketStrategy

public TokenBucketStrategy()

Method Details

check

public boolean check(Bucket bucket,
 LimitConfig cfg,
 long[] out)

Description copied from interface: RateLimitStrategy

Checks whether this request is within the limit and updates the bucket atomically.

On return, out contains:

• out[0] — remaining allowed requests in the current window (≥ 0).
• out[1] — Unix epoch seconds at which the quota resets (for X-RateLimit-Reset and Retry-After headers).

Specified by:

check in interface RateLimitStrategy

Parameters:

bucket - per-key state carrier (pre-allocated, never null)

cfg - immutable rule configuration

out - caller-supplied two-element array; values are overwritten on every call

Returns:

true if the request is within the limit and should proceed