fix(gatsby): use lmdb.removeSync so getNode can't return deleted nodes

[KyleAMathews]

lmdb.remove() is asynchronous so getNode can still return deleted nodes for a time until the delete operation completes.

Switching to removeSync fixes this (at the cost of some amount of perf penalty).

[vladar]

Hmm, something is not right with this PR - it includes commits that were already merged to master?

[wardpeet]

@vladar fixed :)

[vladar]

This seems redundant as getNode has the same check now.

Suggested change

	.map(nodeId => {
	if (preSyncDeletedNodeIdsCache.has(nodeId)) {
	return undefined
	}
	return getNode(nodeId)
	})
	.map(nodeId =>getNode(nodeId)!)

[vladar]

👍

[vladar]

I think this can lead to a race condition when some DELETE_NODE is called while the transaction is being submitted by lmdb in another thread. Ideally, if clear is pending and DELETE_NODE happens we should cancel the previous clear attempt.

Pretty edge case, but it will be very hard to debug if we actually hit it.

[vladar]

🚢

[pieh]

https://app.circleci.com/pipelines/github/gatsbyjs/gatsby/76288/workflows/e843318b-e1c5-4cdf-b155-b82bf562e44e/jobs/898140 shows cases where DELETE_NODE payload might be falsy:

error Cannot read property 'id' of undefined


  TypeError: Cannot read property 'id' of undefined
  
  - lmdb-datastore.ts:218 updateDataStore
    [artifacts]/[gatsby]/src/datastore/lmdb/lmdb-datastore.ts:218:66
  
  - lmdb-datastore.ts:259 callback
    [artifacts]/[gatsby]/src/datastore/lmdb/lmdb-datastore.ts:259:7
  
  - mett.ts:50 forEach
    [artifacts]/[gatsby]/src/utils/mett.ts:50:11
  
  - Set.forEach
  
  - mett.ts:49 Object.emit
    [artifacts]/[gatsby]/src/utils/mett.ts:49:17
  
  - index.ts:153 
    [artifacts]/[gatsby]/src/redux/index.ts:153:11

so we should check if payload is truthy before reaching to id. We do checks like that in other places handling DELETE_NODE action - for example in

gatsby/packages/gatsby/src/datastore/lmdb/updates/nodes.ts

Lines 16 to 21 in 0f421db

	case `DELETE_NODE`: {
	if (action.payload) {
	return nodesDb.remove(action.payload.id)
	}
	return false
	}

[pieh]

also casting payload as IGatsbyNode pretty much removes information that this might be falsy as our action type does mention it:

gatsby/packages/gatsby/src/redux/types.ts

Lines 836 to 840 in 0f421db

	export interface IDeleteNodeAction {
	type: `DELETE_NODE`
	// FIXME: figure out why payload can be undefined here
	payload: IGatsbyNode | void
	}

I really think we should avoid casts like this. In fact none of casts in this line are needed because after checking for type action already become that specific type in closure below