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From Billie Rinaldi <>
Subject Re: Accumulo Standby Master question
Date Wed, 06 Nov 2013 16:32:38 GMT
On Tue, Nov 5, 2013 at 12:51 PM, Josh Elser <> wrote:

> It looks like you can configure multiple hosts for GC and they'll use
> ZooKeeper to perform failover (like the master).
> Tracers -- You can run multiple tracer processes. You likely don't need
> 1:1 as you run tservers, but you can run a few if you're concerned about
> it. They're not required for Accumulo operation.
> Same for the monitor. If you need to have multiple running for failover
> purposes, it looks like you can specify multiple and it will just launch a
> monitor on each host you specified. There's no centralize URL you can
> always hit here. You would have to check each one to find one that was,
> unless you want to run some sort of reverse-proxy in front of them all.

I think additional monitors won't work entirely as expected.  The log
forwarding from the other processes is set up when the processes are
started, and the logs are only sent to the first host in the monitor file.

> _obligatory I just looked to source code to come to this conclusion_
> On 11/5/13, 3:13 PM, Terry P. wrote:
>> I put my secondary namenode in the masters file for the first time with
>> this latest Accumulo 1.4.2 cluster deployment so it would run as a
>> Standby Accumulo Master which I read about in the User Guide.  Recently
>> had the Master lose its Zookeeper lock (network glitch, being
>> researched), and was glad to see the secondary namenode Master process
>> took over as it should.
>> But if my Namenode / Accumulo Master server goes down, I also lose the
>> gc, monitor, and tracer processes as well. *Can I configure the
>> secondary namenode in gc, tracer, and monitor files as well, or should
>> they run on only one host at a time*?  In this case, the GC also lost
>> its Zookeeper lock, which resulted in a cluster with no GC running at
>> all until I caught it.
>> Thanks in advance.

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