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From Jeremy Jongsma <jer...@barchart.com>
Subject Re: Measuring WAN replication latency
Date Wed, 30 Jul 2014 14:40:59 GMT
The brute force way would be:

1) Make client connections to a node in each datacenter from your
monitoring tool.
2) Periodically write a row to one datacenter (at whatever consistency
level your application typically uses.)
3) Immediately query the other datacenter nodes for the same row key with
LOCAL_QUORUM consistency. If not found, execute query again immediately in
a loop.
4) Once the row is available, record time since initial write for that
datacenter.

DataStax folks: this actually seems like a useful metric for something
OpsCenter to track, since it is already doing active statistics collection.


On Wed, Jul 30, 2014 at 8:59 AM, Rahul Neelakantan <rahul@rahul.be> wrote:

> Rob,
> Any ideas you can provide on how to do this will be appreciated, we would
> like to build a latency monitoring tool/dashboard that shows how long it
> takes for data to get sent across various DCs.
>
> Rahul Neelakantan
>
> On Jul 29, 2014, at 8:53 PM, Robert Coli <rcoli@eventbrite.com> wrote:
>
> On Tue, Jul 29, 2014 at 3:15 PM, Rahul Neelakantan <rahul@rahul.be> wrote:
>
>> Does anyone know of a way to measure/monitor WAN replication latency for
>> Cassandra?
>
>
> No. [1]
>
> =Rob
>
> [1] There are ways to do something like this task, but you probably don't
> actually want to do them. Trying to do them suggests that you are relying
> on WAN replication timing for your application, which is something you
> almost certainly do not want to do. Why do you believe you have this
> requirement?
>
>

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