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From Roman Kondakov <kondako...@mail.ru.INVALID>
Subject Re: Metrics for MVCC caches
Date Wed, 08 Aug 2018 10:32:00 GMT
Hi Ivan!

In my opinion we need to preserve the essence of the metrics: if we 
didn't consider dirty writes as updates before MVCC implementation, we 
also shouldn't count these writes in MVCC metrics implementation too. 
So, I think we need to count only committed entries. But we can count 
this dirty writes as additional metrics.

Also additional metrics concerning MVCC could be:

- Average count of the active transactions per snapshot

- Average quantity of versions per key


Roman Kondakov

On 07.08.2018 17:17, Павлухин Иван wrote:
> Hi Igniters,
> I am working on cache metrics support for caches with enabled MVCC. As you
> may know, during MVCC transaction execution entry versions are written to
> storage right away (without deferring until commit). So, it is not obvious
> for me if we should update writes count right away or defer it until
> commit. On one hand, MVCC entry version write is not "true" write until
> commit. On the other hand, it definitely changes the storage. How do we
> interpret write metrics in Ignite philosophy?
> Also, it seems that bunch of MVCC specific metrics could be introduced. I
> would like to collect some thoughts about it. Which such metrics come to
> your mind?

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