1.6 KiB
ADR 012: ABCI Events
Changelog
- 2018-09-02 Remove ABCI errors component. Update description for events
- 2018-07-12 Initial version
Context
ABCI tags were first described in ADR 002. They are key-value pairs that can be used to index transactions.
Currently, ABCI messages return a list of tags to describe an "event" that took place during the Check/DeliverTx/Begin/EndBlock, where each tag refers to a different property of the event, like the sending and receiving account addresses.
Since there is only one list of tags, recording data for multiple such events in a single Check/DeliverTx/Begin/EndBlock must be done using prefixes in the key space.
Alternatively, groups of tags that constitute an event can be separated by a special tag that denotes a break between the events. This would allow straightforward encoding of multiple events into a single list of tags without prefixing, at the cost of these "special" tags to separate the different events.
TODO: brief description of how the indexing works
Decision
Instead of returning a list of tags, return a list of events, where each event is a list of tags. This way we naturally capture the concept of multiple events happening during a single ABCI message.
TODO: describe impact on indexing and querying
Status
Proposed
Consequences
Positive
- Ability to track distinct events separate from ABCI calls (DeliverTx/BeginBlock/EndBlock)
- More powerful query abilities
Negative
- More complex query syntax
- More complex search implementation