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Is it possible to recover a parachain from a backup that is around ~500 blocks behind the head block known by the relay chain?

In single-chains, this is usually not difficult when you control all the validators(collators), but in a multi-chain system, I suspect that it becomes a lot more complex.

If this is possible, I would like to know how complex would it be. And if possible, the recovery steps.

More information:

The relay chain is running BABE and the parachain has a single collator.

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  • Did you implement BABE support on your own for parachains? Otherwise it is not supported. To your question, can you not just take a db backup?
    – bkchr ♦
    Commented Nov 3, 2022 at 23:09
  • The relay chain is the one using BABE, updated the question. I have an old backup of the database, lets say that the database is on block 500 and the relay chain already processed 1000 blocks from that parachain.
    – Rodrigo Quelhas
    Commented Nov 4, 2022 at 7:25
  • I've already re-deployed the parachain, but I would like to know how I could recover from that, if it is even possible.
    – Rodrigo Quelhas
    Commented Nov 4, 2022 at 7:26
  • All the stuff you are saying is very unspecific. You should add more details on what is your actual problem.
    – bkchr ♦
    Commented Nov 4, 2022 at 21:55

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From what I understand you have a stalled parachain, maybe not event running ? From which you kept a db backup.

If that is the scenario you should be able to launch your para with that backup. Assuming the validation function of your parachain is still the same that the one you used to register it on the relay, then you would only need to update the head information on the relaychain for your para.

This can be done via force_set_current_head or set_current_head. Using as new head the state from the last block of your backup.

I would recommend using set_current_head, but both will result in the same.

Though, understand that having to set a new head for your para on the relaychain "manually" is something done in very counted occasions.

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  • Thanks. I will give this a try if it happens again.
    – Rodrigo Quelhas
    Commented Nov 8, 2022 at 19:05

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