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https://issues.apache.org/jira/browse/HBASE-13686?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14543971#comment-14543971
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Matteo Bertozzi commented on HBASE-13686:
-----------------------------------------

{quote}1. In my code, now will be updated in every request. This code is just 
for test shortly.{quote}
yeah, you update now at the beginning of the for loop, but you pass lastTs to 
the checkExecute() and lastTs was not updated with the sleep time (you should 
update now with sleep time before assigning now to lastTs at the end of the 
for) otherwise your check is against an old time that does not include your 
sleep, so that will not refill, because for the RateLimiter you didn't do a 
sleep

> Fail to limit rate in RateLimiter
> ---------------------------------
>
>                 Key: HBASE-13686
>                 URL: https://issues.apache.org/jira/browse/HBASE-13686
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 2.0.0, 1.1.0
>            Reporter: Guanghao Zhang
>            Priority: Minor
>
> While using the patch in HBASE-11598 , I found that RateLimiter can't to 
> limit the rate right.
> {code} 
>  /**
>    * given the time interval, are there enough available resources to allow 
> execution?
>    * @param now the current timestamp
>    * @param lastTs the timestamp of the last update
>    * @param amount the number of required resources
>    * @return true if there are enough available resources, otherwise false
>    */
>   public synchronized boolean canExecute(final long now, final long lastTs, 
> final long amount) {
>     return avail >= amount ? true : refill(now, lastTs) >= amount;
>   }
> {code}
> When avail >= amount, avail can't be refill. But in the next time to call 
> canExecute, lastTs maybe update. So avail will waste some time to refill. 
> Even we use smaller rate than the limit, the canExecute will return false. 



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