zetacore : Discussion for emitting and indexing events

[kingpinXD]

Key Points

• The zeta core emits several events both from default cosmos modules and custom zetachain modules

• The events are part of the blockchain state, and a separate index is maintained by comet-bft to query the events

  • Every app instance (Node) can choose which events to index; This can be set in app.toml

# IndexEvents defines the set of events in the form {eventType}.{attributeKey},
# which informs Tendermint what to index. If empty, all events will be indexed.
#
# Example:
# ["message.sender", "message.recipient"]
index-events = []

• The event indexing uses a KV backend by default , but this can be changed to a PostgreSQL backend. Which might be beneficial for querying the events.This can be set in config.toml

[tx_index]

# What indexer to use for transactions
#
# The application will set which txs to index. In some cases a node operator will be able
# to decide which txs to index based on configuration set in the application.
#
# Options:
#   1) "null"
#   2) "kv" (default) - the simplest possible indexer, backed by key-value storage (defaults to levelDB; see DBBackend).
# 		- When "kv" is chosen "tx.height" and "tx.hash" will always be indexed.
#   3) "psql" - the indexer services backed by PostgreSQL.
# When "kv" or "psql" is chosen "tx.height" and "tx.hash" will always be indexed.
indexer = "kv"

• List of events emitted by Zetacore
  https://www.notion.so/zetachain/Events-1907b3fb9049809280bbdc8be4cda1e4?pvs=4

Recommendations

• Index only events which are querying so that tx_index.db can be optimised.
• Explore plsql backend for some nodes , it might improve query performance also make it easier to query the events.
• Remove events which are unnecessary to help reduce the growth of the application state.