pruner: use teeWriter and HEAD as prune target, fix genesis root validation

[curryxbo]

Problems

1. Genesis root validation failure during pruning

During prune-state, extractGenesis calls trie.NewSecure with the genesis block's root. On Morph, the genesis root stored in the block header may be a zkTrie root (overridden via GenesisStateRoot for block hash compatibility) rather than the actual MPT disk root, causing trie.NewSecure to fail and aborting the entire pruning process.

2. Block height regression after pruning

The pruner previously targeted HEAD-127 as the prune target, meaning after pruning the node would restart at a state 127 blocks behind the actual chain head. On L2 chains like Morph where reorgs are essentially non-existent, this safety margin is unnecessary and causes undesirable height rollback.

Solution

• Genesis root fix: In extractGenesis, resolve the genesis root via rawdb.ReadDiskStateRoot before opening the trie, so the actual MPT disk root is used even when the header contains a zkTrie root.
• teeWriter: Writes trie nodes to both the real database and the bloom filter during GenerateTrie, ensuring trie data is fully persisted to disk regardless of how the node was previously shut down.
• HEAD as prune target: Use HEAD directly instead of HEAD-127. Combined with teeWriter, this guarantees zero height drop after pruning.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Refactor
  • Ensured trie nodes are reliably persisted to disk during state operations.
  • Simplified and made pruning target selection more consistent and predictable.
  • Adjusted genesis initialization to resolve and prefer on-disk state roots when available, improving startup consistency.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 7df699b7-6c0d-42f0-b5bb-9011e4733fed

📥 Commits

Reviewing files that changed from the base of the PR and between f1d36d4 and 007b8b5.

📒 Files selected for processing (1)

• core/state/pruner/pruner.go

🚧 Files skipped from review as they are similar to previous changes (1)

• core/state/pruner/pruner.go

---

📝 Walkthrough

Walkthrough

Added an unexported teeWriter to duplicate trie-node writes to DB and stateBloom; changed Pruner.Prune to default to p.headHeader.Root when root is zero and removed middleRoots logic; updated trie generation to use the writer; resolved genesis root via rawdb.ReadDiskStateRoot.

Changes

Cohort / File(s)	Summary
Pruner & trie persistence core/state/pruner/pruner.go	Added unexported teeWriter that forwards Put/Delete to the underlying DB and records writes to stateBloom; Pruner.Prune now defaults zero root to p.headHeader.Root and removes snapshot-layer/middleRoots selection; snapshot.GenerateTrie invoked with the writer; extractGenesis resolves genesis root via rawdb.ReadDiskStateRoot before creating the trie.

Sequence Diagram(s)

sequenceDiagram
    participant Pruner
    participant Snapshot as snapshot.GenerateTrie
    participant Tee as teeWriter
    participant DB as KeyValueDB
    participant Bloom as stateBloom

    Pruner->>Snapshot: GenerateTrie(snaptree, root, db, writer)
    Snapshot->>Tee: Put/Delete(node)
    Tee->>DB: Put/Delete(node)
    Tee->>Bloom: Record(node)
    Tee-->>Snapshot: ack
    Snapshot-->>Pruner: trie generation complete

Loading

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~50 minutes

Possibly related PRs

• pruner: fall back to disk snapshot root when journal is missing #300: Modifies Pruner.Prune target-root selection and related pruning fallback logic in the same file.

Suggested labels

bug

Suggested reviewers

• twcctop
• panos-xyz

Poem

🐰 I hop through nodes both quiet and spry,
I write to disk and whisper to the sky.
Two paths for each leaf — persistent and bright,
Prune by HEAD now, trimming through the night. ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately captures the three main changes: introducing teeWriter, changing the prune target to HEAD, and fixing genesis root validation.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch pruner/tee-writer-and-head-target

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 golangci-lint (2.11.4)

Error: can't load config: unsupported version of the configuration: "" See https://golangci-lint.run/docs/product/migration-guide for migration instructions
The command is terminated due to an error: can't load config: unsupported version of the configuration: "" See https://golangci-lint.run/docs/product/migration-guide for migration instructions

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[coderabbitai]

Actionable comments posted: 1

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

core/state/pruner/pruner.go (1)

267-304: ⚠️ Potential issue | 🟠 Major

Preserve middleStateRoots for explicit non-HEAD targets.

This path now always calls prune(..., nil, ...), but prune() only force-deletes intermediate snapshot roots when that map is populated. RecoverPruning still builds middleRoots for the same reason. If a caller prunes to an older user-specified root, the intermediate diff-layer roots can survive bloom false-positives and leave dangling state behind.

Suggested fix

 func (p *Pruner) Prune(root common.Hash) error {
+	var middleRoots map[common.Hash]struct{}
+
 	if root == (common.Hash{}) {
 		// Use HEAD as the pruning target. On L2 chains reorgs are
 		// essentially non-existent, so the HEAD-127 safety margin
@@
 		root = p.headHeader.Root
 		log.Info("Selecting HEAD as the pruning target", "root", root, "height", p.headHeader.Number.Uint64())
 	} else {
 		log.Info("Selecting user-specified state as the pruning target", "root", root)
+
+		found := false
+		layers := p.snaptree.Snapshots(p.headHeader.Root, 128, true)
+		middleRoots = make(map[common.Hash]struct{})
+		for _, layer := range layers {
+			if layer.Root() == root {
+				found = true
+				break
+			}
+			middleRoots[layer.Root()] = struct{}{}
+		}
+		if !found {
+			return errors.New("non-existent target state")
+		}
 	}
@@
-	return prune(p.snaptree, root, p.db, p.stateBloom, filterName, nil, start)
+	return prune(p.snaptree, root, p.db, p.stateBloom, filterName, middleRoots, start)
 }

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@core/state/pruner/pruner.go` around lines 267 - 304, The current path always
calls prune(..., nil, ...) which prevents prune() from force-deleting
intermediate snapshot roots; when pruning to an explicit non-HEAD root you must
preserve and pass the middleStateRoots map so intermediate diff-layer roots are
removed. Modify the code that selects the target root (the branch where root !=
(common.Hash{})) to build or reuse the same middleStateRoots map constructed by
RecoverPruning (or compute it the same way) and pass that map into prune(...)
instead of nil (keep using prune(p.snaptree, root, p.db, p.stateBloom,
filterName, middleStateRoots, start)). Ensure the symbol middleStateRoots is
populated before the call and used in prune so intermediate roots are cleaned
up.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@core/state/pruner/pruner.go`:
- Around line 382-389: The code currently treats any error from
rawdb.ReadDiskStateRoot as “mapping absent” and silently falls back to
genesis.Root(); update the logic around rawdb.ReadDiskStateRoot(genesisRoot) so
only a not-found/missing mapping is ignored—propagate or return any real DB/read
errors instead. Specifically, modify the genesisRoot resolution block that calls
rawdb.ReadDiskStateRoot and assigns genesisRoot (and the subsequent
trie.NewSecure call) to check the error kind (or replace ReadDiskStateRoot with
a helper that returns (mptRoot, ok, err)); if ok==false keep genesisRoot, but if
err!=nil return/log the error up the call stack instead of swallowing it. Ensure
callers of this function handle the returned error appropriately.

---

Outside diff comments:
In `@core/state/pruner/pruner.go`:
- Around line 267-304: The current path always calls prune(..., nil, ...) which
prevents prune() from force-deleting intermediate snapshot roots; when pruning
to an explicit non-HEAD root you must preserve and pass the middleStateRoots map
so intermediate diff-layer roots are removed. Modify the code that selects the
target root (the branch where root != (common.Hash{})) to build or reuse the
same middleStateRoots map constructed by RecoverPruning (or compute it the same
way) and pass that map into prune(...) instead of nil (keep using
prune(p.snaptree, root, p.db, p.stateBloom, filterName, middleStateRoots,
start)). Ensure the symbol middleStateRoots is populated before the call and
used in prune so intermediate roots are cleaned up.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 83e20ed3-68f5-4843-85d0-723903ce8d75

📥 Commits

Reviewing files that changed from the base of the PR and between af017cb and ac47fab.

📒 Files selected for processing (1)

• core/state/pruner/pruner.go