Make light client refresh window configurable

[nik-suri]

Summary

Currently Hermes has the light client refresh rate hardcoded in - it'll automatically refresh the light client every 2/3rd of the trusting period and this rate is not configurable. The only way to get more frequent refreshes is to lower the trusting period, which is not the ideal path. We would ideally like to configure multiple refresh attempts within the trusting period, instead of waiting until 2/3rd of trusting period has elapsed.

Problem Definition

This would be a useful feature to add further protection against an IBC light client going stale. For example, we currently have a light client with a trusting period of 2 days. In the worst case, there could be 0 packets sent, the relayer could go down right before the light client refresh is scheduled to happen, and we may not realize the relayer is down until the full trusting period has elapsed. If we could configure the relayer to make more frequent updates to the light client, we'd be very well protected against this scenario.

Proposal

Perhaps we could implement this feature through a flag in each chain config. This way, each chain could configure a custom light client refresh rate.

For example, light_client_refresh_rate = 1/5 would schedule a light client update to happen once 1/5 of the trusting period elapses.

Acceptance Criteria

A feature is implemented that enables the user to configure custom light client refresh rates for each chain in the hermes config.

---

For Admin Use

• Not duplicate issue
• Appropriate labels applied
• Appropriate milestone (priority) applied
• Appropriate contributors tagged
• Contributor assigned/self-assigned

[romac]

Can you try out this branch and see if it works for you? #3402

The new per-chain setting is client_refresh_rate and it takes for value a fraction of the trusting period, eg. '1/10' for refreshing the client 10 times per trusting period.

[romac]

@nik-suri Can you try out this branch and see if it works for you? #3402