how to solve Detected prevote equivocation in the finality worker issue?

Question

I am getting this issue after performing the solution of this issue How can we restart the chain if it becomes stuck during data migration?

Tried to run the existing chain with new chain spec with bad blocks and new binary with all validators then it started producing block also doing the block finalization.

We basically started with 2 validators then chain started producing blocks then we added all validators then it started finalizing blocks also. After that chain produced about 130 blocks and finalizing also. Then with old chainspec and binary we started achieve node then chain finality stopped with below error in log.

Sep 23 12:33:51 node[3498514]: 2023-09-23 12:33:51 Detected prevote equivocation in the finality worker: Equivocation { round_number: 6425345, identity: Public(f87122bdc0f31343bba1c1b8f11e1584e5ed42234ce479df89608aecde43260d (5HgTLj1r...)), first: (Prevote { target_hash: 0x842a42a7556d5f338411f1dafc08a87daf855a7f4284a8ea3032fd5d1c6e0a43, target_number: 1440577 }, Signature(55b96a8677651787154021323d3853cccdb1ee98b33dda98afaaf75e0bd9f61a22d0af8567561898e2b5dd4519325b220ee55cc908d007b9032a06d3188c5706)), second: (Prevote { target_hash: 0xac2fbb087b3b2f89ce6e4e23f4587ce9038c26ef7f673750ef60496f6346f7da, target_number: 1440676 }, Signature(f75ca444dfab57bc72f340413c813941daf5b0e5c7e129e29b0ff6f9a9e943e102f94b97d115d0e95ade1436ebea7568a15ced586c660d6b7615cdb57dc0d50e)) }

Answer 1

There aren't enough details in this question to be able to solve your problem. If when you started the archive node you stated seeing GRANDPA equivocations it means that this node is actually voting. Regardless, if finality is not progressing it also means that not enough validators are voting (you need >2/3 of the validators online to be able to finalize). It's also possible that some validators are voting on blocks that the others can't import, I am not sure if you added badBlocks to the chain spec, but if you did, you need to do this for all validators and not just a few. Have a look at these questions which can help you debug your issue:

• https://substrate.stackexchange.com/a/380/452
• https://substrate.stackexchange.com/a/668/452

Edit: is the archive node running as a validator? Also please check the answers above, in particular the usage of the grandpa_roundState RPC endpoint to figure out what is the current state of the round (i.e. who is not voting). You can also run your nodes with -lgrandpa=debug and check for a log message like Waiting to import block {hash} before {N} round messages can be imported. This should indicate that someone is voting on a chain that descends from badBlocks, probably because you didn't update all the validators to the new chainspec at once. Since the nodes with the new chainspec will refuse to import those blocks, this means that the round doesn't make progress (since they can't process those votes).