bug: Zebra panics with "Sprout note commitment tree must exist if there is a finalized tip" shortly after launch

[teor2345]

What happened?

I expected to see this happen:

Zebra always launches successfully.

Instead, this happened:

Zebra panics with "Sprout note commitment tree must exist if there is a finalized tip" shortly after launch.

What were you doing when the issue happened?

Testing the subtree code in PR #7566 on my local machine
Testing unrelated code on my local machine
Running unrelated PRs in CI

Zebra logs

Exit Status:
command terminated unsuccessfully by signal 6
Stdout:
Stderr:
The application panicked (crashed).
Message: Sprout note commitment tree must exist if there is a finalized tip
Location: zebra-state/src/service/finalized_state/zebra_db/shielded.rs:97
Metadata:
failures:
config_tests

Zebra Version

zebrad 1.2.0, multiple commits on different PRs

Which operating systems does the issue happen on?

• Linux
• macOS
• Windows
• Other OS

OS details

various machines: CI, local machine

Additional information

The panic is from the expect() in:

zebra/zebra-state/src/service/finalized_state/zebra_db/shielded.rs

Lines 84 to 98 in 4f6d28f

	/// Returns the Sprout note commitment tree of the finalized tip
	/// or the empty tree if the state is empty.
	pub fn sprout_tree(&self) -> Arc<sprout::tree::NoteCommitmentTree> {
	let height = match self.finalized_tip_height() {
	Some(h) => h,
	None => return Default::default(),
	};
	let sprout_nct_handle = self.db.cf_handle("sprout_note_commitment_tree").unwrap();
	self.db
	.zs_get(&sprout_nct_handle, &height)
	.map(Arc::new)
	.expect("Sprout note commitment tree must exist if there is a finalized tip")
	}

This issue should be fixed by PR #7392.

It might be possible for remote nodes to trigger this bug, or make it more likely, because it happens when a block is downloaded during launch. (Or maybe while writing another block.)

[teor2345]

This just happened again on my local machine.

[mpguerra]

@teor2345 can you please add an estimate here?