execmodule: send notifications before DB commit

[mh0lt]

Summary

Move Hook.AfterRun calls to fire before flush+commit in the FCU and ProcessFrozenBlocks paths. Currently notifications are sent after tx.Commit() via a fresh db.View(), adding unnecessary latency and coupling to committed DB state.

Background

The original reason for post-commit notifications (comment in events.go:276): "need send notification after rwtx.Commit (or user will recv notification, but can't request new data by RPC)".

Investigation confirms this concern is no longer valid:

Consumer	Reads DB after notification?
Filters.onNewHeader	No — decodes from RLP payload
RecentReceipts subscribers	No — uses payload proto
Coherent.OnNewBlock	No — updates in-memory btree from payload
EthBackendServer.Subscribe	No — forwards to gRPC stream

All notification consumers use the payload data directly and never read back from the DB.

Change

The pipeline's RwTx/overlay already contains all data that notifications read (headers, stage progress, forkchoice hashes, state version). Pass it directly to AfterRun before flush+commit.

Two sites changed:

• runForkchoiceCommit (forkchoice.go) — AfterRun moved before sd.Flush + tx.Commit
• ProcessFrozenBlocks (stageloop.go) — AfterRun moved before tx.Commit, db.View() removed

Two sites already pre-commit (unchanged):

• stageLoopIteration — already uses the RwTx before commit
• ProcessFrozenBlocks intermediate loop — already uses the RwTx

Relationship to other work

• Rationalize IntraBlockState to a 2-Cache Model #19623 (2-cache IBS rationalization): After Phase 3, SharedDomains becomes the single authoritative inter-block state. This change aligns the notification path with that direction — reads go through the in-memory layer rather than requiring a committed DB tx.
• execution: extract apply loop into event stream with fan-out consumers #19798 (event stream extraction): The Accumulator.SendAndReset() call moved pre-commit will be restructured into a fan-out notifyConsumer.
• Design: TransactionState/BlockState separation, TxTask refactoring, cross-process TX caching #19855 (TransactionState/BlockState separation): Interface changes there will further simplify the notification path.

Also documents the execmodule.Cache shim's role and relationship to these issues.

Branch

feat/pre-commit-notifications — not ready to PR yet, waiting for dependent work.

[VBulikov]

yperbasis added Imp2 as Importance