[Feature] Copy a subgraph at specific block height

[madumas]

Description

Copying a subgraph at a specific block height would allow for an elegant alternative to rewinds when a divergence is identified in a subgraph.

Proposed workflow
1 - Identify divergence point N
2 - copy subgraph at block height N
3 - Allow graph-node to fully sync the copy
4 - Verify that the divervence is resolved
5 - use graphman copy activate to gracefully direct traffic to the corrected subgraph

Are you aware of any blockers that must be resolved before implementing this feature? If so, which? Link to any relevant GitHub issues.

No response

Some information to help us out

• Tick this box if you plan on implementing this feature yourself.
• I have searched the issue tracker to make sure this issue is not a duplicate.

[github-actions]

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[lutter]

That's already possible with graphman copy create --offset. It's a little wonky since it takes an offset from the current subgraph head rather than an absolute block number, but I hope that works well enough for your use case. LMK if we should make changes.

[madumas]

We use graphman copy create --offset exactly as described here, as a "parallel rewind", and it works well, aside from having to compute the offset against a head that keeps moving.

There's one case the same workflow can't cover today: pruned subgraphs. --offset requires the base block to be at or after the source's earliest_block_number (see #6607 / #6610), and for a pruned deployment the divergence point is very often below that. So the parallel rewind isn't available at all, and re-indexing from scratch is the only way out.

What we'd want is the same workflow, but with the new deployment syncing from its start block instead of grafting from the source: it indexes in parallel while the current one keeps serving queries, then graphman copy activate switches traffic over with no downtime.