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.
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.
