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feat: Optimistic Execution #16581

Merged
merged 39 commits into from
Sep 18, 2023
Merged

feat: Optimistic Execution #16581

merged 39 commits into from
Sep 18, 2023

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facundomedica
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@facundomedica facundomedica commented Jun 15, 2023

Description

RFC: #16499
Closes: #XXXX


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baseapp/abci.go Fixed Show fixed Hide fixed
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@facundomedica
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I think we need to be especially careful when OE is aborted, because finalizeBlockState could be left in a bad state.

  1. InitChain happens, finalizeBlockState is not nil
  2. During FinalizeBlock we check if finalizeBlockState == nil, otherwise we re-use it (because we want to be able to access any state written during InitChain)
  3. If we abort, we need to be able to reset to the state that we had right after InitChain.

Maybe to keep it simple we can execute OE only if height > initialHeight. That way we can just clear up the state 100% of the times

baseapp/abci.go Outdated
Comment on lines 492 to 498
// processed the first block, as we want to avoid overwriting the finalizeState
// after state changes during InitChain.
if req.Height > app.initialHeight {
// abort any running OE
if app.oeEnabled && app.oeInfo != nil && app.oeInfo.Running() {
app.oeInfo.Abort()
_, _ = app.oeInfo.WaitResult() // ignore the result
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Change potentially affects state.

Call sequence:

(*github.com/cosmos/cosmos-sdk/baseapp.BaseApp).ProcessProposal (baseapp/abci.go:467)

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baseapp/optimistic_execution.go Fixed Show fixed Hide fixed
baseapp/optimistic_execution.go Fixed Show fixed Hide fixed
baseapp/oe/optimistic_execution.go Fixed Show fixed Hide fixed
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I tried cleaning up the concurrency model with little success, now I'm passing a context to internalFinalizeBlock which makes it unaware of the whole OE thing, it uses this context just to know if it needs to return early.

Using channels is a cleaner way to do this, but the problem is that the function we are passing as our FinalizeBlockFn has access to baseapp and to its properties, so we have partial control over what's going on with the state. This ended up in getting wrong app hashes from time to time.

A great improvement would be to have FinalizeBlock to use only whatever is passed to it and with little to no access to baseapp. This way we could run the entire block completely concurrently by passing only cached copies of the contexts and values; and by the time we abort we just discard all of these.
On the other hand, this could complicated this a bunch given that we'd need to make sure no other process modifies the base contexts and values being passed. Also I don't know if it's possible at all without a major refactor on baseapp

Comment on lines +101 to +110
go func() {
start := time.Now()
resp, err := oe.finalizeBlockFunc(ctx, oe.request)
oe.mtx.Lock()
executionTime := time.Since(start)
oe.logger.Debug("OE finished", "duration", executionTime.String(), "height", req.Height, "hash", hex.EncodeToString(req.Hash))
oe.response, oe.err = resp, err
close(oe.stopCh)
oe.mtx.Unlock()
}()

Check notice

Code scanning / CodeQL

Spawning a Go routine Note

Spawning a Go routine may be a possible source of non-determinism
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facundomedica and others added 2 commits August 29, 2023 12:18
Co-authored-by: Aleksandr Bezobchuk <alexanderbez@users.noreply.github.com>
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I've added a check so we don't start optimistic execution when ProcessProposal returns a "reject"

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@julienrbrt julienrbrt left a comment

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mostly doc nits.

@@ -241,7 +242,7 @@ func NewSimApp(
voteExtHandler := NewVoteExtensionHandler()
voteExtHandler.SetHandlers(bApp)
}
baseAppOptions = append(baseAppOptions, voteExtOp)
baseAppOptions = append(baseAppOptions, voteExtOp, baseapp.SetOptimisticExecution())
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Is it purposely done so that simapp only uses optimistic execution?
Or should we add it here:

baseapp.SetQueryGasLimit(cast.ToUint64(appOpts.Get(FlagQueryGasLimit))),
?

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So I wouldn't like to add a flag for this, because that could give node operators the chance of not running optimistic execution if the developers chose to do so (they can still modify the code but that takes some extra effort).
Could we add a flag on simapp only? wdyt?

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@julienrbrt julienrbrt Sep 18, 2023

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Yeah, a flag wouldn't make sense.
I was taking about adding it in our default baseapp options.
But I think I remember conversation about having it disabled by default first 🤔, so it makes sense to add it only in simapp.

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utACK!

@facundomedica facundomedica added this pull request to the merge queue Sep 18, 2023
Merged via the queue into main with commit 8df065b Sep 18, 2023
47 of 49 checks passed
@facundomedica facundomedica deleted the facu/oe branch September 18, 2023 14:12
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@Mergifyio backport release/v0.50.x

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mergify bot commented Oct 23, 2023

backport release/v0.50.x

✅ Backports have been created

mergify bot pushed a commit that referenced this pull request Oct 23, 2023
Co-authored-by: Aleksandr Bezobchuk <alexanderbez@users.noreply.github.com>
(cherry picked from commit 8df065b)

# Conflicts:
#	CHANGELOG.md
#	baseapp/abci_test.go
CASABECI

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julienrbrt pushed a commit that referenced this pull request Oct 23, 2023
Co-authored-by: Facundo Medica <14063057+facundomedica@users.noreply.github.com>
Co-authored-by: Facundo <facundomedica@gmail.com>
@CASABECI

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CASABECI

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Great work @facundomedica 👏

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6 participants