Rate limiting for the Ethereum event oracle

[james-chf]

namada/apps/src/lib/node/ledger/ethereum_node/oracle.rs

Lines 122 to 128 in 60a0c99

	async fn run_oracle_aux(oracle: Oracle) {
	// Initialize our local state. This includes
	// the latest block height seen and a queue of events
	// awaiting a certain number of confirmations
	let mut latest_block;
	let mut pending: Vec<PendingEvent> = Vec::new();
	loop {

Currently, the Ethereum event oracle checks for new blocks/events as soon as it has finished the previous check. We should back off inbetween checks (e.g. sleep 1 second), so that we don't spam the Ethereum JSON-RPC endpoint we are using, or spam logs.

Extra context - #253 (comment)