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From Ted Yu <yuzhih...@gmail.com>
Subject Re: Canary Test Tool and write sniffing
Date Sat, 04 Feb 2017 16:40:44 GMT
Brief search on HBASE-4393 didn't reveal why the interval was shortened.

If you read the first paragraph of:
http://hbase.apache.org/book.html#_run_canary_test_as_daemon_mode

possibly the reasoning was that canary would exit upon seeing some error
(the first time).

BTW There was a mismatch in the description for this command: (5 seconds
vs. 50000 milliseconds)

${HBASE_HOME}/bin/hbase canary -daemon -interval 50000 -f false


On Sat, Feb 4, 2017 at 8:21 AM, Lars George <lars.george@gmail.com> wrote:

> 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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