RFC: mongo "_id" fields in the multi-environment juju server world

[roger peppe]

On 7 July 2014 14:27, Gustavo Niemeyer <gustavo at niemeyer.net> wrote:
> On Mon, Jul 7, 2014 at 10:09 AM, roger peppe <roger.peppe at canonical.com> wrote:
>> I had assumed that because every client needs to see every transaction
>> there would likely be no benefit to sharding the log, although
>> technically you could shard on transaction id. I'd be
>
> Clients don't need to see every transaction. Only those that affect
> the documents they are acting on.

Is it actually possible to shard the transaction log based on the documents
the transactions are acting on? I couldn't see a straightforward
way to do it, with the existing transaction log structure at least.

>> Thanks for pointing this out. If we manage to hugely scale juju using mongodb
>> I will be very happy. I still think we should do some measurements to
>> convince us that we actually have some hope of doing so though.
>> My own measurements left me less than convinced of the
>> possibility, although it's been a while since I did them.
>
> When you measured a sharded setup, what was the outcome?

I simply measured operation rate (of some actual juju operations)
on a non-sharded setup. I saw around 60 operations per second.
It may well have been that I was testing an inefficient setup, or
that my mongo settings were inadequate.