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From: Alexander Shraer <shralex@gmail.com>
Date: Thu, 22 Jun 2017 22:39:01 -0700
Message-ID: <CANcXBFMHsGgLzS4+bTg2gRpO=00wtRtgw1dt-YWw==yegR03dg@mail.gmail.com>
Subject: Re: How to add nodes to a Zookeeper 3.5.3-beta ensemble with reconfigEnabled=false
To: "user@zookeeper.apache.org" <user@zookeeper.apache.org>
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archived-at: Fri, 23 Jun 2017 05:39:29 -0000

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Hi Michael,

The described behavior is the intended one - in 3.5 configuration is part
of the synced state and is updated
when the server syncs with the leader. The only rolling upgrade I tested
was to upgrade the software version
of the servers - this should still work. But I didn't try to support
rolling upgrade for upgrading the configuration,
since this should be done through reconfig.

I'm still not sure what's the purpose of this flag btw. Why would someone
want to do rolling restarts which are prone
to inconsistencies and data loss, when they can use reconfig ?

Alex


On Thu, Jun 22, 2017 at 10:18 PM, Michael Han <hanm@cloudera.com> wrote:

> reconfigEnabled only disables reconfig command when reconfigEnabled=false;
> it does not disable the feature by mute all code paths of the reconfig
> feature introduced in ZOOKEEPER-107. So regardless of the value of
> reconfigEnabled,
> 3.5.x ZK will create static config file and dynamic config file in any
> cases.
>
> This might create a problem for users who want to do rolling upgrade the
> old way - because now the critical config information is not stored in
> zoo.cfg anymore and modifying cfg.dynamic file manually will not work
> because a reconfig needs to go through quorum processors. I think this is
> the problem described in the thread.
>
> Alex, is reconfig compatible with rolling upgrade? I don't find anything
> mentioned in ZOOKEEPER-107 about this. Currently I think the answer is no,
> which means for 3.5.x the only way to change membership of cluster is
> through reconfig. Could you confirm this conclusion? If that is the case we
> need patch the reconfigEnabled so it completely disable all code path of
> the reconfig feature to leave the static zoo.cfg intact.
>
>
> On Thu, Jun 22, 2017 at 9:35 PM, Alexander Shraer <shralex@gmail.com>
> wrote:
>
> > This sounds like a bug in the implementation of reconfigEnabled.
> > Could you please open a JIRA with the description you provided ?
> >
> > Out of curiosity, why do you disable reconfig ? It is intended exactly
> > to perform the changes you're trying to make, in a simple and correct
> way.
> >
> > Thanks,
> > Alex
> >
> > On Thu, Jun 22, 2017 at 3:17 PM, Guillermo Vega-Toro <
> gvegator@us.ibm.com>
> > wrote:
> >
> > > I'm still unable to make configuration changes when
> reconfigEnabled=false
> > > by updating zoo.cfg and restarting the servers.
> > >
> > > For example, I want to change the weight of one of my servers. I edit
> > > zoo.cfg on the server I want to change, and specify the group,
> server.x,
> > > and weight.x properties for all servers. I also remove the
> > > dynamicConfigFile property and delete the dynamic config file. I then
> > > restart the server. As soon as the server starts, the dynamic config
> file
> > > re-appears, and it has the last configuration, as if the changes I made
> > in
> > > zoo.cfg were ignored. The dynamic configuration file on the other
> servers
> > > also stays the same.
> > >
> > > What would be the correct way to achieve this (change a server's
> weight,
> > > or role) when reconfigEnabled=false and the CLI reconfig command cannot
> > be
> > > used?
> > >
> > > Thanks
> > >
> > >
> >
>
>
>
> --
> Cheers
> Michael.
>

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