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From Lars George <lars.geo...@gmail.com>
Subject Re: Canary Test Tool and write sniffing
Date Sat, 04 Feb 2017 16:21:32 GMT
Oh right, Ted. An earlier patch attached to the JIRA had 60 secs, the
last one has 6 secs. Am I reading this right? It hands 6000 into the
Thread.sleep() call, which takes millisecs. So that makes 6 secs
between checks, which seems super short, no? I might just dull here.

On Sat, Feb 4, 2017 at 5:00 PM, Ted Yu <yuzhihong@gmail.com> wrote:
> For the default interval , if you were looking at:
>
>   private static final long DEFAULT_INTERVAL = 6000;
>
> The above was from:
>
>     HBASE-4393 Implement a canary monitoring program
>
> which was integrated on Tue Apr 24 07:20:16 2012
>
> FYI
>
> On Sat, Feb 4, 2017 at 4:06 AM, Lars George <lars.george@gmail.com> wrote:
>
>> Also, the default interval used to be 60 secs, but is now 6 secs. Does
>> that make sense? Seems awfully short for a default, assuming you have
>> many regions or servers.
>>
>> On Sat, Feb 4, 2017 at 11:54 AM, Lars George <lars.george@gmail.com>
>> wrote:
>> > Hi,
>> >
>> > Looking at the Canary tool, it tries to ensure that all canary test
>> > table regions are spread across all region servers. If that is not the
>> > case, it calls:
>> >
>> > if (numberOfCoveredServers < numberOfServers) {
>> >   admin.balancer();
>> > }
>> >
>> > I doubt this will help with the StochasticLoadBalancer, which is known
>> > to consider per-table balancing as one of many factors. In practice,
>> > the SLB will most likely _not_ distribute the canary regions
>> > sufficiently, leaving gap in the check. Switching on the per-table
>> > option is discouraged against to let it do its thing.
>> >
>> > Just pointing it out for vetting.
>> >
>> > Lars
>>

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