Light Clients – Do Light-Clients Still Work After The Merge

consensuslight-clientsnodesthe-merge

After the merge, my light client suddenly stopped working. Is there a way to fix this/ do I need to run a consensus node?

Thank you!

Best Answer

The syncing functionality of the geth light node does not currently (Nov 2022) work post-merge, because the historical execution layer blocks are no longer sufficient to light-verify the chain. There is an open PR to add support for standalone beacon chain light syncing in geth here: https://github.com/ethereum/go-ethereum/pull/25901

This is only the first step to restoring the expected functionality of the geth light node. I expect it won't be until early 2023 when the expected functionality is restored.

Related Solutions

Running Light Client Server – How to Run a Server for Ethereum Light Clients

A light server is a full node with "LES server" option enabled. This option is disabled by default (at least as long as the LES implementation is still in experimental stage), so light clients actually DO need a somewhat "special" endpoint. Run

geth --lightserv 25

to allocate max. 25% of CPU resources for serving clients.

Peer discovery is also experimental, LES uses a PoC test version of the planned new RLPx v5 discovery protocol that allows searching specifically for a certain kind of nodes (light servers in our case). It takes a few minutes for the server to start advertising itself on the network.

Go Ethereum – What Geth Version is Needed for Ethereum Merge?

You will need at least Geth version 1.10.23 (Sentry Omega).

https://blog.ethereum.org/2022/08/24/mainnet-merge-announcement

In addition to Geth (an execution layer client), you will also need to run a consensus layer client as in the announcement above, and then authenticate (connect) them as described below.

Install a consensus layer client

https://ethereum.org/en/upgrades/merge/#preparing-for-the-merge

Assuming you are a Non-validating node operator, key action items include:

Install a consensus layer client in addition to an execution layer client
Authenticate execution and consensus clients with a shared JWT secret so they can securely communicate with one another.

Authenticating the clients

https://launchpad.ethereum.org/en/merge-readiness/#authenticate

Communication between the execution layer and consensus layer will occur using the Engine API. This is a new set of JSON RPC methods that can be used to communicate between the two client layers.

Instructions for how to set this JWT secret vary depending on the client — node operators should refer to their clients' documentation for instructions about how to generate and configure these.