On Fri, Oct 14, 2016 at 2:16 AM, Jay Juma <jayk.j...@gmail.com> wrote:

> based on my understanding, a global cluster can be setup to spread over
> multiple datacenters and the data placement policy will place the data over
> multiple datacenters.
>
> My question is "is it possible to create a log stream on a global cluster
> that just write to bookies within same datacenter".
>

In theory, yes. However currently the data placement policy is configured
per cluster.

We can consider pushing down the data placement policy as part of the log
segment metadata. So that bookie auto-recovery will be aware of what data
placement policy will be used for re-replicating/recovering a bookkeeper
ledger.


>
> I had two use cases, one is for database replication. for example, if there
> are 2 datacenters A and B. A global dl cluster is setup over A and B. The
> database cluster in A will write updates into a (some) global log
> stream(s), and the database in B will tail-read those streams and apply
> changes. I think this is a very typical use case of DistributedLog, right?
>
> There is another use case, it is just used for replication within one
> datacenter. It doesn't need to replicate to the other datacenter. We want
> to share the DL cluster for these two use cases. Is there a way to achieve
> that? by tuning the data placement policy for individual streams?
>

Typically we don't mix global replicated log with local replicated log. But
it seems that making data placement policy configurable per stream is a
good option for your use case.


Do you mind creating a JIRA for us to track this use case?


>
> Let me know if you need more information. Appreciate your help.
>
> Thanks,
> Jay
>

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