RateLimit-Reset Header : getting time to wait for refill even limit is not exceeded

[xavier-b]

Hi,

It would be interesting to get remaining time for a refill, even if the limit is not reached. This allows client to not exceed the limit.
Today, we have to exceed the limit to know how many time before refill.

Indeed, ConsumptionProbe.getNanosToWaitForRefill() return zero if limit not exceeded.
https://github.com/vladimir-bukhtoyarov/bucket4j/blob/8a6333b2653ae17da6d32211260d4968a03cea78/bucket4j-core/src/main/java/io/github/bucket4j/ConsumptionProbe.java#L104-L111

Extract of RateLimit Header Fields for HTTP draft-polli-ratelimit-headers-00 :

A client SHOULD NOT exceed the quota-units expressed in RateLimit-Remaining before the time-window expressed in RateLimit-Reset.

Actually, with bucket4j, it's not possible to have RateLimit-Reset without exceed the limit. Isn't it ?

[vladimir-bukhtoyarov]

@xavier-b

Hello, ConsumptionProbe#getNanosToWaitForRefill has nothing in common with RateLimit-Reset. As mentioned in the javadocs, it returns the time required to refill requested amount of tokens, not the time required to refill tokens up to max possible values.

To get such information you need to use Verbose API:

VerboseResult<ConsumptionProbe> result = bucket.asVerbose().tryConsumeAndReturnRemaining(1);
ConsumptionProbe probe = result.getValue();
Diagnostics diagnostics = result.getDiagnostics();
if (probe.isConsumed()) {
    long nanosToRefillUpToLimit = diagnostics.calculateFullRefillingTime();
    ...
} else {
    long nanosToRefillUpToLimit = diagnostics.calculateFullRefillingTime();
    long nanosToRefillRequestedTokens = probe.getNanosToWaitForRefill();
    ...
}

See this doc for more details https://bucket4j.com/7.0.0/toc.html#verbose-api especially this https://bucket4j.com/7.0.0/toc.html#example-of-verbose-api-usage

[xavier-b]

Thanks,
That works fine.
That makes more sense to use it with "intervally" refill.
When do you expect to be able to release 6.4.1 ?

[vladimir-bukhtoyarov]

6.4.1 was released last week https://mvnrepository.com/artifact/com.github.vladimir-bukhtoyarov/bucket4j-core/6.4.1