New Use Case for Stateful CNF

[sishbi]

Hello,
@Smitholi67 and @sishbi have created a new use-case covering a Stateful CNF.
This is captured by the following PR: #165
We can discuss the use-case either in the PR directly or here.
@taylor We would like to add this PR / discussion to the agenda for the weekly call.

[taylor]

I think it would be good for the glossary to have terms for different types of state. Eg. ephemeral, cache, user data

[taylor]

Watson shared some comments:

Different types of people (programmer, network engineer, chaos testing) have different definitions of state and resiliency.

The main types, for me, are in memory and on disk. What needs to persist and what does not?

What are the latency requirements?

cc: @sishbi @wavell @denverwilliams

[sishbi]

@taylor When you say 'glossary' do you mean the CNF-WG glossary or the glossary in this use-case? And just to clarify, you are asking for a description of the different types of state that exist and examples of each? (Such as ephemeral is state that can be lost without consequence, such as a temporary file within a Pod)

[wvwatson]

https://github.com/cncf/cnf-wg/tree/main/use-case/0003-UC-stateful-cnf
"The low latency requirements may result in a solution where state is stored in-memory"
"The state that is a maintained by the Stateful CNF must remain ACID complaint, a convergent charging system handles real-time financial transactions"

https://en.wikipedia.org/wiki/In-memory_database#:~:text=ACID%20support,-See%20also%3A%20Atomicity&text=Volatile%20memory%2Dbased%20IMDBs%20can,a%20given%20moment%20in%20time.
"In its simplest form, main memory databases store data on volatile memory devices. These devices lose all stored information when the device loses power or is reset. In this case, IMDBs can be said to lack support for the "durability" portion of the ACID (atomicity, consistency, isolation, durability) properties. Volatile memory-based IMDBs can, and often do, support the other three ACID properties of atomicity, consistency and isolation."

Just FYI a lot of old school DBAs don't think in memory DBs are ACID compliant, because of durability.

[sishbi]

Thanks @wavell - but if the IMDB is specifically designed to include 'durability' features that allow the memory contents to be recreated - would that be sufficient to be 'ACID' ?