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Date: Fri, 15 May 2015 10:40:00 +0000 (UTC)
From: "Ashish Singhi (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Commented] (HBASE-13686) Fail to limit rate in RateLimiter
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    [ https://issues.apache.org/jira/browse/HBASE-13686?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14545289#comment-14545289 ] 

Ashish Singhi commented on HBASE-13686:
---------------------------------------

bq.  As long as user's request rate is samller than 60 in one minute, the RateLimiter should guarantee the request canExecute.
Yes, I totally understand that and even we have internally thought about it. We are internally discussing on this to get to a conclusion.

> 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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