EPIC: Events

[tac0turtle]

Summary

Events have been used by many applications for internal state machine actions and external clients. There has been confusion on where events should be used and where they should not. Recently we saw Juno halt due to a misunderstanding of how events are emitted and thus incorrect reliance of nondeterministic ordering of events in the cosmos-sdk. While events are non deterministic it is unclear at which stage they are non-deterministic.

Problem Definition

It is unclear who events are for and what is the safest way to use them?

Work Breakdown

Things we can do today:

• [ ] define events determinism and who are the primary consumers of events
• [ ] Organise a break out call with ecosystem partners to discuss deeper about how events should act and how they should be treated.
• [ ] populate msg responses of proto messages in order to use these with cosmwasm and potentially other applications
• [ ] Fix non-determinism in any events

Related/Future Work:

• [ ] Typed events ADR
• [ ] ADR-033
• [ ] further work can be discussed

[migueldingli1997]

Hi, has there been any development around this? I have a use-case where I'm thinking of iterating over the events generated by modules (at BeginBlock) in my custom module's BeginBlock, and would like to understand if this is not recommended.

(I've posted this as a forum post on Discord as well just in case that's a better place for this)

[migueldingli1997]

Hi, has there been any development around this? I have a use-case where I'm thinking of iterating over the events generated by modules (at BeginBlock) in my custom module's BeginBlock, and would like to understand if this is not recommended.

(I've posted this as a forum post on Discord as well just in case that's a better place for this)

The replies I've gotten from Discord indicate that the order of events can differ between one node and another, and so these should ideally be sorted if we're going to iterate over them.