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Date: Fri, 10 Feb 2017 09:45:42 +0000 (UTC)
From: "Corentin Chary (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
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Subject: [jira] [Commented] (CASSANDRA-13159) Coalescing strategy can enter
 infinite loop
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archived-at: Fri, 10 Feb 2017 09:45:47 -0000


    [ https://issues.apache.org/jira/browse/CASSANDRA-13159?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15861000#comment-15861000 ] 

Corentin Chary commented on CASSANDRA-13159:
--------------------------------------------

LGTM

> Coalescing strategy can enter infinite loop
> -------------------------------------------
>
>                 Key: CASSANDRA-13159
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13159
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Streaming and Messaging
>            Reporter: Corentin Chary
>            Assignee: Corentin Chary
>             Fix For: 3.0.11, 2.1.x, 2.2.x, 3.11.x
>
>
> {code}boolean maybeSleep(int messages, long averageGap, long maxCoalesceWindow, Parker parker){code} 
> maybeSleep() can enter an infinite loop if messages or averageGap ends up being 0 because sleep will be 0 and the while loop will never exit. I've noticed that on one of my clusters twice this week.
> This can happen if in averageGap() sum is bigger than MEASURED_INTERVAL, which should be pretty rare but apparently happen to me.
> Even if the diagnostic is wrong (and I'm pretty sure that this thread was using 100% CPU doing nothing), the fix seems pretty safe to apply.
> {code}
> diff --git a/src/java/org/apache/cassandra/utils/CoalescingStrategies.java b/src/java/org/apache/cassandra/utils/CoalescingStrategies.java
> index 0aa980f..982d4a6 100644
> --- a/src/java/org/apache/cassandra/utils/CoalescingStrategies.java
> +++ b/src/java/org/apache/cassandra/utils/CoalescingStrategies.java
> @@ -100,7 +100,7 @@ public class CoalescingStrategies
>      {
>          // only sleep if we can expect to double the number of messages we're sending in the time interval
>          long sleep = messages * averageGap;
> -        if (sleep > maxCoalesceWindow)
> +        if (!sleep || sleep > maxCoalesceWindow)
>              return false;
>  
>          // assume we receive as many messages as we expect; apply the same logic to the future batch:
> {code}


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