feat: snapshot: remove existing chain

[rjan90]

Related Issues

Closes: #10958

Proposed Changes

Add a flag (remove-existing-chain) to remove the existing chain data on import of a snapshot, reducing manual operation needed when node operators want to prune their current chain.

Additional Info

Some open questions:

• Do we only want the removal of the chain data to be possible when importing a snapshot?
  • Do we want it to default to true when importing a snapshot?
• Do we want to clear the chain data dirs, or delete it?
  • Are there any edge-cases where deleting the chain data dir is bad before importing a snapshot?

Testing:

• Tested on a node without SplitStore
• Tested on a node with SplitStore

Docs (todo):

• Update this section: https://lotus.filecoin.io/lotus/manage/chain-management/#compacting-the-chain-data

Checklist

Before you mark the PR ready for review, please make sure that:

• Commits have a clear commit message.
• PR title is in the form of of <PR type>: <area>: <change being made>
  • example: fix: mempool: Introduce a cache for valid signatures
  • PR type: fix, feat, build, chore, ci, docs, perf, refactor, revert, style, test
  • area, e.g. api, chain, state, market, mempool, multisig, networking, paych, proving, sealing, wallet, deps
• New features have usage guidelines and / or documentation updates in
  • Lotus Documentation
  • Discussion Tutorials
• Tests exist for new functionality or change in behavior
• CI is green

[rjan90]

Do we want it to be the default to true when importing a snapshot?

With regards to this:

• Defaulting it to true would help a lot of new users which may not be familiar with the need to remove the existing chain data before importing a Snapshot. But if we want to go in this direction, I think we need to only make it possible when importing a snapshot.

[ZenGround0]

Overall looks good, has it been tested?

[rjan90]

Overall looks good, has it been tested?

It has been tested on a node running with SplitStore, and on a node running without SplitStore and it removed the chain data successfully on both before starting the import of the snapshot.

Two question I have for you @ZenGround0 is:

• What is the difference between clearSplitstoreDir and deleteSplitstoreKeys functions in the lotus-shed splitstore clear command you created are (I borrowed code from that)? I currently use deleteSplitstoreDir as it seemed most applicable for what we wanted to achieve here, but would like to understand the nuance.
• Are there any edge-cases where deleting the SplitStore dir is wrong vs just its content. Afaik the folder is re-created if its not there, which should be fine during reimporting of snapshots.

[rjan90]

Updated the PR with some changes based on feedback/reviews:

• Removed unused clearSplitStoreDir function ()
• Originally I had this:

  lotus/cmd/lotus/daemon.go

  Lines 313 to 317 in 5201744

  	cfg, err := lockedRepo.Config()
  	if err != nil {
  	lockedRepo.Close()
  	return xerrors.Errorf("error getting config: %w", err)
  	}

  
  But Andy shared that If .Config() panics, close won't happen here. So I extracted the removeExistingChain function, and used defer to ensure that the lockedRepo is closed, even if a panic occurs. (dedfa14)
• Fixed errCheck

[rjan90]

Testing on a SplitStore-node:

[Chainstore]
  # type: bool
  # env var: LOTUS_CHAINSTORE_ENABLESPLITSTORE
  EnableSplitstore = true

See that there is data in the chain-folder:

/mnt/lotuschain/.lotus/datastore/chain$ ls
000000.vlog  000010.vlog  000020.vlog  000030.vlog  000040.vlog  000050.vlog  000060.vlog  000070.vlog  000080.vlog  000090.vlog  000320.sst  000453.sst  000522.sst  000555.sst  000605.sst  000615.sst  000629.sst  000639.sst
-----

See that there is data in the splitstore-folder:

/mnt/lotuschain/.lotus/datastore/splitstore$ ls
hot.badger  markset.badger

Run lotus daemon --import-snapshot /home/3005040_2023_07_04T08_00_00Z.car.zst --remove-existing-chain=true --halt-after-import

....
2023-07-04T15:24:02.887+0200	INFO	main	lotus/daemon.go:774	removing splitstore directory...
2023-07-04T15:24:03.709+0200	INFO	main	lotus/daemon.go:787	removing chain directory:/mnt/lotuschain/.lotus/datastore/chain
2023-07-04T15:24:12.949+0200	INFO	main	lotus/daemon.go:794	chain and splitstore data have been removed
......
2023-07-04T15:24:13.058+0200	INFO	main	lotus/daemon.go:543	importing chain from /home/3005040_2023_07_04T08_00_00Z.car.zst...
 382.48 MiB / 49.02 GiB [=>--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------]   0.76% 21.15 MiB/s 39m10s

Check that existing chain data was removed before the import-snapshot started:

/mnt/lotuschain/.lotus/datastore$ ls
chain  client  metadata  staging

And

/mnt/lotuschain/.lotus/datastore/chain$ ls
000000.vlog  KEYREGISTRY  LOCK  MANIFEST

[ZenGround0]

Thanks for bearing with the late review here

What is the difference between clearSplitstoreDir and deleteSplitstoreKeys

I forget what I was doing, the clear.. function doesn't delete the top level dir, you used the simpler / better one. One thing however: I think we should confirm that if you delete the splitstore data and run the node with splitstore then it correctly recreates the splitstore dir on startup. I think you might have already tested this, just double checking.

Docs (todo):

Since we're not making this the default I think we're good to merge without changing chain management docs.