baseline topology questions

[narges saleh <sn...@gmail.com>]

Hi All,
Sorry if these questions are too basic.

1) How does cache replication work in context of native persistence,
especially in context of WAL files? Do the primary and replication node
have separate WAL files?
2) How does baseline topology work in context of kubernetes, with
persistent storage volume enabled? When a pod dies,  and is replaced with a
new pod,
  a) does the cache gets rebuilt from the persisted data to disk on the
hosting node or
  b) does it reloaded from its replica cache (assuming cache was configured
with replicated option)? or
  c) does rebalancing occur with creation of a replacement pod? If yes,
what happens to the data on disk?
  d) does the replacement pod automatically assume the id of the lost pod
(as far basline topology is concerned)?

thanks.

Re: baseline topology questions

[Stephen Darlington <st...@gridgain.com>]

Persistence doesn’t change anything about the distribution of data. It also doesn’t change anything about “rebalancing” the data. The only real difference is that you trigger rebalancing by changing the baseline topology manually, a process that is generally automatic when you use Ignite in-memory-only. Using Kubernetes doesn’t change anything about how Ignite works.

With that said:

1) It doesn’t change anything. All nodes have a copy of the data (including WAL) as before.
2) 
a) What do you mean by “the pod dies”? If you mean it crashed and restarted, yes, the data will just come from disk as long as it connects to the same PV. If you mean you lost the pod and the PV then data would have to be copied from another node (after you manually altered the baseline topology)
b) As above
c) No. Rebalancing happens when you change the baseline topology.
d) If the new pod picks up the “old” PV, yes.

> On 11 Feb 2020, at 03:56, narges saleh <sn...@gmail.com> wrote:
> 
> Hi All,
> Sorry if these questions are too basic.
> 
> 1) How does cache replication work in context of native persistence, especially in context of WAL files? Do the primary and replication node have separate WAL files?
> 2) How does baseline topology work in context of kubernetes, with persistent storage volume enabled? When a pod dies,  and is replaced with a new pod, 
>   a) does the cache gets rebuilt from the persisted data to disk on the hosting node or 
>   b) does it reloaded from its replica cache (assuming cache was configured with replicated option)? or
>   c) does rebalancing occur with creation of a replacement pod? If yes, what happens to the data on disk?
>   d) does the replacement pod automatically assume the id of the lost pod (as far basline topology is concerned)?
> 
> thanks.