eth/v1/node/syncing endpoint returns wrong value

[eenagy]

Describe the bug

Prysm returns true for el_offline after el connected, this should be false.

Has this worked before in a previous version?

Not sure.

🔬 Minimal Reproduction

1. Start any el client

besu  --rpc-http-enabled --data-path=$HOME/.run-a-node/sepolia --network=SEPOLIA --engine-jwt-secret=$HOME/.run-a-node/sepolia/jwt.hex --rpc-http-api=ETH --rpc-http-port=8545

2. Start prysm

beacon-chain  --accept-terms-of-use --sepolia --datadir=$HOME/.run-a-node/sepolia --checkpoint-sync-url=https://beaconstate-sepolia.chainsafe.io --disable-grpc-gateway=false --execution-endpoint=http://localhost:8551 --genesis-beacon-api-url=https://beaconstate.info --grpc-gateway-port=5052 --http-modules=eth --jwt-secret=$HOME/.run-a-node/sepolia/jwt.hex

3. Wait until you see the message the Connected to new endpoint endpoint=http://localhost:8551
4. Check for status

curl -s -X GET -H Content-Type: application/json http://localhost:5052/eth/v1/node/syncing

See that the el_offline is true instead of false

{"data":{"head_slot":"5450336","sync_distance":"131","is_syncing":true,"is_optimistic":false,"el_offline":true}}

For this test, I have included besu, but same result with erigon/geth/nethermind/reth. All other CL client will return false when EL is connected.

Error

No response

Platform(s)

Linux (x86)

What version of Prysm are you running? (Which release)

beacon-chain version Prysm/v5.0.4/3b184f43c86baf6c36478f65a5113e7cf0836d41. Built at: 2024-06-21 00:26:00+00:00

Anything else relevant (validator index / public key)?

No response

[james-prysm]

I don't believe this is a bug, it'll return "el_offline":true if it's not synced to head. if the execution client returns any errors it'll retry and the endpoint will return "el_offline":true

[eenagy]

According to the specs, this looks like a bug: Beacon Node Syncing Endpoint.

I've tested this endpoint with several clients before reporting it. lighthouse, lodestar, nimbus-eth2, and teku all report true initially, then false; however, prysm seems inconsistent with the other clients.

I have a work-in-progress branch where I test client configs against each other; if that helps, please check it out.

[james-prysm]

perhaps other clients are returning false when it's syncing? will followup with my teammate

[eenagy]

@james-prysm I don't think the sync status has anything to do with el_offline. All other clients initially return (true) then when execution client is connected they return false. If you disconnect (shut down the client), they change the status back to true.
I'm basing this on what I see happening when values are returned.