Skip to main content

expired-client

Goal​

In this guide, we review why and how IBC clients expire, as well as review the process to update an expired client.

Why Do Clients Expire?​

Trusting Period​

Clients expire when TrustingPeriod has passed since the last updated client state. This is usually due to lack of use of the ibc channel, or lack of active relayers.

It is recommended that TrustingPeriod should be set as 2/3 of the UnbondingPeriod of the network.

How is a Client Updated Normally?​

These command are usually ran by a relayer during the ibc transaction workflow to update the state of a client for a channel:

hermes update client --host-chain <chain-id> --client <client>

Steps to carry out the process of reviving the IBC client:​

  1. Determine which client is expired and on which host chain
  2. Create a new client on that host chain
  3. Push a proposal on-chain that replaces the expired client-id with an active newly created one
  4. Check if the channel is once again operational

1. Check for Expired Clients​

You will know if a client is expired if your ibc tx fails, and the error logs communicates that the client is expired. You can also get the status of a client with:

hermes query client state --chain chain-id --client 07-tendermint-123

2. Create a New Client on Host Chain​

hermes tx client

3. Create Governance Proposal To Update Expired Client​

to propose to update an expired client:

terpd tx gov submit-legacy-proposal update-client [subject-client-id] [substitute-client-id] [flags]

References​