juju HA lands on tip

[roger peppe]

That's great! Thanks Andrew.

On 21 April 2014 21:43, Andrew Wilkins <andrew.wilkins at canonical.com> wrote:
> On Fri, Apr 18, 2014 at 3:02 AM, roger peppe <rogpeppe at gmail.com> wrote:
>>
>> I've just landed some changes on juju tip that enable "highly available"
>> juju environments. In a HA environment, there are several state servers -
>> if one dies, one of the others should take over.
>>
>> To make a HA environment, run the "ensure-availability" command. For
>> example to make a HA environment with three state servers, run:
>>
>> $ juju ensure-availability -n 3
>>
>> This will add new servers as necessary. It will also maintain the
>> current state server set if some servers have gone down.
>>
>> A new field in the status output, state-server-member-status, present
>> only for state server machines, indicates the current status of each
>> state server.
>>
>> When the status of a majority of state server machines is "has-vote",
>> the environment should be resilient to any one of them going down.
>>
>> If a state server machine goes down and you run ensure-availability again,
>> it should detect that the machine has gone down and create a new machine
>> to replace it. When the new machine is available, the original (down)
>> machine's status will become "no-vote".
>>
>> If you run ensure-availability again, it will see that the machine has
>> no vote and is down, and will remove its state server status. At that
>> point the machine can actually be removed (you'll need the --force flag).
>>
>> Anyone that's interested, please try it out. It would be great if people
>> could see whether it works for them - there are bound to be some teething
>> problems!
>>
>> There is one major caveat: upgrading an existing environment
>> to HA is not supported currently (Andrew Wilkins has a branch in review
>> that
>> should fix this).
>
> Upgrade support landed on the weekend. If would be great it some intrepid
> users would test this out. (I have tested it, of course.)
>
>>
>> Please note that the transition times when mongo is failing over can be
>> quite long (on the order of minutes), so you'll need to be patient.
>>
>> Many thanks to everyone that's pitched in to help get this done.
>>
>> cheers,
>> rog.
>>
>>
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>