SDK Simulation debt

[fedekunze]

The simulation framework of the SDK has a high technical debt that would need to be addressed. I think outlining the current problems, goals for a stable implementation and the actionable items.

Goals:

• Fuzz test txs within the SDK for a given number of blocks
• Test IBC transactions (possibly through localhost client)
• Test export -> import functionality
• Benchmarks / Stats (?)

Some issues (feel free to add):

• Simulation module (x/simulation): this is not technically a module and needs to be removed from the x/ folder. The core logic hasn't been updated in a long time
• Non-modular: While the app module simulation allowed for modules to register their own decoders, transactions, and custom parameters for the application to run, the x/simulation package doesn't allow other keys for both validators and accounts.
• Statistics: the simulation can export stats that are not largely used and don't provide a large number of insights.
• Weighted Operations: They are not really "weighted". The simulation just generates a random number 0-100 and checks if the random number is less than the total "weight".

Ref issues: #7009, #7129, #5664
Simulation docs

cc: @alexanderbez @aaronc @clevinson

[aaronc]

Yep I've definitely noticed some of these things too. Would be great to put this on the roadmap sometime this year.

[hxrts]

@marbar3778 is looking into finding a dedicated owner for the simulator.

[tac0turtle]

Note: I am trying to find someone to refactor but the maintenance of the simulator has always fallen under the scope of the sdk maintainers and still should IMO

[fedekunze]

FYI current docs are located here: https://docs.cosmos.network/v0.42/building-modules/simulator.html and https://pkg.go.dev/github.com/cosmos/[email protected]/x/simulation