Chainindex passthrough when behind backing validator #796

AloeareV · 2026-01-15T15:04:14Z

Fixes: #769

This PR adds a validator_finalized_height field to a snapshot. If this height is higher than the snapshot's tip, most APIs will pass requests through to the backing validator.

…aw_transaction passthrough

idky137 · 2026-01-20T15:11:39Z

Hey I've been mulling over the problem with testing this functionality and came up with a possible solution (you may have already fixed this but thought I would add this in case it has not been possible to implement in the "MockChainSource".

I think one way we could implement the test only "Stop finalised state syncing at block X" is to add a "test" feature flagged field ("pause_sync_at_height?) to the "BlockCacheConfig" struct (or we could define a "TestVariables" struct to be added as this new field?):

zaino/zaino-state/src/config.rs

Line 136 in 31d0d85

pub struct BlockCacheConfig {

Then under the same "test" feature flag stop writing to the finalised state at the given block height in "start_sync_loop":

zaino/zaino-state/src/chain_index.rs

Line 520 in 31d0d85

fs.write_block(next_finalized_block.clone())

It may still be cleaner to implement this in the "MockChainSource" if possible but that could be more intrusive than just adding here.

AloeareV · 2026-01-22T18:22:04Z

Hey I've been mulling over the problem with testing this functionality and came up with a possible solution (you may have already fixed this but thought I would add this in case it has not been possible to implement in the "MockChainSource".

I think one way we could implement the test only "Stop finalised state syncing at block X" is to add a "test" feature flagged field ("pause_sync_at_height?) to the "BlockCacheConfig" struct (or we could define a "TestVariables" struct to be added as this new field?):

zaino/zaino-state/src/config.rs

Line 136 in 31d0d85

pub struct BlockCacheConfig {

Then under the same "test" feature flag stop writing to the finalised state at the given block height in "start_sync_loop":

zaino/zaino-state/src/chain_index.rs

Line 520 in 31d0d85

fs.write_block(next_finalized_block.clone())

It may still be cleaner to implement this in the "MockChainSource" if possible but that could be more intrusive than just adding here.

I just thought of something, which I'm gonna try out...if we add a customizable delay to MockchainSource methods, we could do some experimentation with simulated network latency...and if we make the delay long enough, it could slow sync down to a crawl, and still allow passthroughs to go through (as a passthrough requires one or maybe two calls to the source, a one-second delay would mean that the passthrough takes a couple seconds, and syncing a block would also take seconds, so if we make the chain a few hundred blocks we won't catch up to the finalized boundary before the request comes in.)

AloeareV · 2026-01-29T16:35:09Z

An open question: When a passthrough request is made, and the needed information is in the nonfinalized state, is this:

An Ok(None) return, as if we and the validator were synced to the top of the finalized range
An Error return, indicating that the information requested exists but isn't synced yet
Something else?

If 2, do we just return this error whenever it's convenient (i.e., when we don't need to additional work to distinguish between the requested information being nonfinalized or nonexistent), or do we make the guarantee of correctly identifying this error in all cases?
Also, if 2, if the request covers multiple blocks and some of them are finalized, do we consider this a success case and return everything finalized, or an error case as the request covered information in the nonfinalized state that we can't safely serve until we've caught up to it? Possibly even vary by specific case/method?

AloeareV · 2026-01-29T18:04:22Z

Still to be done:

Make sure passthrough only triggers when the validator's finalized tip is ahead of ChainIndexes best (nonfinalized) tip.
Some error handling
Fix passthrough triggering before local lookup in some RPCs

zaino-state/src/chain_index.rs

fluidvanadium · 2026-01-30T23:56:54Z

zaino-state/src/chain_index.rs

+        }
+
+        // if the tranasction isn't finalized on the best chain
+        // check our indexes


should we check the index first?

zaino-state/src/chain_index.rs

AloeareV · 2026-02-02T20:18:43Z

zaino-state/src/chain_index/non_finalised_state.rs

                SyncError::ReorgFailure(String::from("could not determine best chain"))
            }
+            UpdateError::ValidatorConnectionError => SyncError::ZebradConnectionError(todo!(
+                "don't have a request error. \


To any reviewers: I would appreciate help figuring out what to do with this error case.

I will look into it.

AloeareV · 2026-02-02T20:20:10Z

zaino-state/src/chain_index/non_finalised_state.rs

+            .await
+            .map_err(|e| InitError::InvalidNodeData(Box::new(e)))?
+            .ok_or_else(|| {
+                InitError::InvalidNodeData(todo!("we need something that implements error"))


As well as this error case

Move sapling-crypto dependency to near other zcash dependencies. Add chain_index_passthrough.mmd. Add this diagram to ChainIndex doc comments.

Add flow comments. Remove unwraps.

… for NodeBackedChainIndexSubscriber<Source> for consistency.

…r efficiency.

…gh and find_fork_point.

fluidvanadium · 2026-02-05T01:42:01Z

Why do self.get_fullblock_bytes_from_node and self.blockchain_source.get_block look so different? shouldnt they be sister functions?

zaino-state/src/chain_index/non_finalised_state.rs

nachog00 · 2026-02-05T14:14:46Z

zaino-state/src/chain_index/non_finalised_state.rs

+            .source
+            .get_best_block_height()
+            .await
+            .map_err(|_| UpdateError::ValidatorConnectionError)?


this sort of mapping i think is a bit troublesome, as it essentially hides any trace of the original error. I think the correct way of mapping it would be some way in the higher error can be traced back to the original through .source().

Ah, I think this was meant to be a todo!

Added a source error to the enum variant!

Ciptbz by diagram 3

AloeareV · 2026-02-05T20:48:28Z

Why do self.get_fullblock_bytes_from_node and self.blockchain_source.get_block look so different? shouldnt they be sister functions?

How do you mean 'so different'? They're not sisters, one calls the other. get_fullblock_bytes_from_node calls get_block and then serializes it to a vec.

(Originally, I somehow edited your message with my answer. I've turned it into a reply now)

…alized_state's copy of it

AloeareV added 7 commits January 12, 2026 17:37

add validator_tip to snapshot

4e4cc64

add get_block_height passthrough

2fdaa0c

add passthrough to get_block_range

c2db013

add passthrough to find_fork_point

471f07f

remove unneeded option

92cf246

update/add comments

e77ea70

modify BlockchainSource::get_transaction for use in ChainIndex::get_r…

46c486c

…aw_transaction passthrough

fluidvanadium self-assigned this Jan 19, 2026

AloeareV added 4 commits January 20, 2026 15:40

add passthrough to get_raw_transaction

6027d64

Merge branch 'dev' into chainindex_passthrough_behind_zebra

7735a94

add get_transaction_status passthrough

02a56e2

fix a couple todos

8aa3b4c

AloeareV added 4 commits January 23, 2026 15:00

update comments

00a1107

test boilerplate

92bacdc

test now shows sync sucessfully slowed-down

0a93120

test get_raw_transaction passthrough

62a42d3

AloeareV force-pushed the chainindex_passthrough_behind_zebra branch from ea266dd to 62a42d3 Compare January 27, 2026 16:56

DRY passthrough_test

c10e799

AloeareV added 2 commits January 29, 2026 13:05

add get_block_height passthrough test

9d7cef2

comment

4172e36

add find_fork_point passthrough test

02959d4

AloeareV force-pushed the chainindex_passthrough_behind_zebra branch from 9f49584 to 02959d4 Compare January 29, 2026 18:34

AloeareV added 2 commits January 29, 2026 15:12

add get_transaction_status passthrough

61fa7e1

add get_block_range passthrough test

c5d7653

fluidvanadium reviewed Jan 30, 2026

View reviewed changes

Merge branch 'dev' into chainindex_passthrough_behind_zebra

1698752

AloeareV commented Feb 2, 2026

View reviewed changes

AloeareV and others added 17 commits February 2, 2026 16:27

fix get block range

1b1b958

un-todo error cases

12229ff

Add mermaid dependency to zaino-state.

36d6bc2

Move sapling-crypto dependency to near other zcash dependencies. Add chain_index_passthrough.mmd. Add this diagram to ChainIndex doc comments.

Reweave find_fork_point.

0bee199

Add flow comments. Remove unwraps.

Simplify syntax flow in get_indexed_block_height.

f288916

Simplify get_block_height syntax flow.

1ebaf99

Replace unwrap in get_transaction_status.

de3d207

Change symbol get_snapshot_block_height -> get_indexed_block_height.

dbd2a8f

Change parameter symbols in trait ChainIndex for consistency.

582e787

Change parameter symbols in impl<Source: BlockchainSource> ChainIndex…

8af9ccc

… for NodeBackedChainIndexSubscriber<Source> for consistency.

Replace unwraps in get_block_height_passthrough.

9ecebaa

Rename parameter symbols nonfinalized_snapshot -> snapshot.

2706044

Handle missing coinbase_height as an Error instead of None.

8b5e085

Comment on how get_block_range may eventually need to be rewritten fo…

624ea75

…r efficiency.

Remove stale comment on find_fork_point.

a381c08

Clarified the necessary condition of finality in passthrough diagram.

04883da

Re-activated finality inequality checks in get_block_height_passthrou…

5305531

…gh and find_fork_point.

nachog00 reviewed Feb 5, 2026

View reviewed changes

zaino-state/src/chain_index/non_finalised_state.rs Outdated Show resolved Hide resolved

nachog00 reviewed Feb 5, 2026

View reviewed changes

Merge pull request #814 from zingolabs/ciptbz_by_diagram_3

a4853ff

Ciptbz by diagram 3

AloeareV added 2 commits February 5, 2026 16:49

fix missing OkSome, use blockchain source directly instead of non_fin…

939d6df

…alized_state's copy of it

rename ZebradConnectionError to ValidatorConnectionError and add source

289c11a

AloeareV marked this pull request as ready for review February 5, 2026 20:56

actually fix get_block_range

cd79d43

Chainindex passthrough when behind backing validator #796

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Chainindex passthrough when behind backing validator #796

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AloeareV commented Jan 15, 2026

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