Return a transaction verifier from `zebra_consensus::init` (#2665)

* Return a transaction verifier from `zebra_consensus::init`

This verifier is temporarily created separately from the block verifier's
transaction verifier.

* Return the same transaction verifier used by the block verifier

* Clarify that the mempool verifier is the transaction verifier

Co-authored-by: Deirdre Connolly <deirdre@zfnd.org>

Co-authored-by: Deirdre Connolly <deirdre@zfnd.org>
Co-authored-by: Conrado Gouvea <conrado@zfnd.org>

zebra-consensus/src/block.rs

@@ -29,21 +29,21 @@ use zebra_chain::{
 };
 use zebra_state as zs;
 
-use crate::{error::*, transaction as tx};
-use crate::{script, BoxError};
+use crate::{error::*, transaction as tx, BoxError};
 
 pub mod check;
 mod subsidy;
+
 #[cfg(test)]
 mod tests;
 
 /// Asynchronous block verification.
 #[derive(Debug)]
-pub struct BlockVerifier<S> {
+pub struct BlockVerifier<S, V> {
     /// The network to be verified.
     network: Network,
     state_service: S,
-    transaction_verifier: tx::Verifier<S>,
+    transaction_verifier: V,
 }
 
 // TODO: dedupe with crate::error::BlockError
@@ -72,18 +72,17 @@ pub enum VerifyBlockError {
     Commit(#[source] BoxError),
 
     #[error("invalid transaction")]
-    Transaction(#[source] TransactionError),
+    Transaction(#[from] TransactionError),
 }
 
-impl<S> BlockVerifier<S>
+impl<S, V> BlockVerifier<S, V>
 where
     S: Service<zs::Request, Response = zs::Response, Error = BoxError> + Send + Clone + 'static,
     S::Future: Send + 'static,
+    V: Service<tx::Request, Response = tx::Response, Error = BoxError> + Send + Clone + 'static,
+    V::Future: Send + 'static,
 {
-    pub fn new(network: Network, state_service: S) -> Self {
-        let transaction_verifier =
-            tx::Verifier::new(network, script::Verifier::new(state_service.clone()));
-
+    pub fn new(network: Network, state_service: S, transaction_verifier: V) -> Self {
         Self {
             network,
             state_service,
@@ -92,10 +91,12 @@ where
     }
 }
 
-impl<S> Service<Arc<Block>> for BlockVerifier<S>
+impl<S, V> Service<Arc<Block>> for BlockVerifier<S, V>
 where
     S: Service<zs::Request, Response = zs::Response, Error = BoxError> + Send + Clone + 'static,
     S::Future: Send + 'static,
+    V: Service<tx::Request, Response = tx::Response, Error = BoxError> + Send + Clone + 'static,
+    V::Future: Send + 'static,
 {
     type Response = block::Hash;
     type Error = VerifyBlockError;
@@ -195,7 +196,9 @@ where
             use futures::StreamExt;
             while let Some(result) = async_checks.next().await {
                 tracing::trace!(?result, remaining = async_checks.len());
-                result.map_err(VerifyBlockError::Transaction)?;
+                result
+                    .map_err(Into::into)
+                    .map_err(VerifyBlockError::Transaction)?;
             }
 
             // Update the metrics after all the validation is finished

zebra-consensus/src/block/tests.rs

@@ -1,6 +1,6 @@
 //! Tests for block verification
 
-use crate::parameters::SLOW_START_INTERVAL;
+use crate::{parameters::SLOW_START_INTERVAL, script};
 
 use super::*;
 
@@ -9,7 +9,7 @@ use std::sync::Arc;
 use chrono::Utc;
 use color_eyre::eyre::{eyre, Report};
 use once_cell::sync::Lazy;
-use tower::buffer::Buffer;
+use tower::{buffer::Buffer, util::BoxService};
 
 use zebra_chain::{
     block::{self, Block, Height},
@@ -20,6 +20,8 @@ use zebra_chain::{
 };
 use zebra_test::transcript::{ExpectedTranscriptError, Transcript};
 
+use crate::transaction;
+
 static VALID_BLOCK_TRANSCRIPT: Lazy<
     Vec<(Arc<Block>, Result<block::Hash, ExpectedTranscriptError>)>,
 > = Lazy::new(|| {
@@ -119,7 +121,13 @@ async fn check_transcripts() -> Result<(), Report> {
     let network = Network::Mainnet;
     let state_service = zebra_state::init_test(network);
 
-    let block_verifier = Buffer::new(BlockVerifier::new(network, state_service.clone()), 1);
+    let script = script::Verifier::new(state_service.clone());
+    let transaction = transaction::Verifier::new(network, script);
+    let transaction = Buffer::new(BoxService::new(transaction), 1);
+    let block_verifier = Buffer::new(
+        BlockVerifier::new(network, state_service.clone(), transaction),
+        1,
+    );
 
     for transcript_data in &[
         &VALID_BLOCK_TRANSCRIPT,

zebra-consensus/src/chain.rs

@@ -12,17 +12,15 @@
 //! Otherwise, verification of out-of-order and invalid blocks and transactions can hang
 //! indefinitely.
 
-#[cfg(test)]
-mod tests;
-
-use displaydoc::Display;
-use futures::{FutureExt, TryFutureExt};
 use std::{
     future::Future,
     pin::Pin,
     sync::Arc,
     task::{Context, Poll},
 };
+
+use displaydoc::Display;
+use futures::{FutureExt, TryFutureExt};
 use thiserror::Error;
 use tower::{buffer::Buffer, util::BoxService, Service, ServiceExt};
 use tracing::instrument;
@@ -38,21 +36,26 @@ use crate::{
     block::BlockVerifier,
     block::VerifyBlockError,
     checkpoint::{CheckpointList, CheckpointVerifier, VerifyCheckpointError},
-    BoxError, Config,
+    error::TransactionError,
+    script, transaction, BoxError, Config,
 };
 
-/// The bound for the chain verifier's buffer.
+#[cfg(test)]
+mod tests;
+
+/// The bound for the chain verifier and transaction verifier buffers.
 ///
 /// We choose the verifier buffer bound based on the maximum number of
 /// concurrent verifier users, to avoid contention:
-///   - the `ChainSync` component
-///   - the `Inbound` service
-///   - a miner component, which we might add in future, and
+///   - the `ChainSync` block download and verify stream
+///   - the `Inbound` block download and verify stream
+///   - the `Mempool` transaction download and verify stream
+///   - a block miner component, which we might add in future, and
 ///   - 1 extra slot to avoid contention.
 ///
 /// We deliberately add extra slots, because they only cost a small amount of
 /// memory, but missing slots can significantly slow down Zebra.
-const VERIFIER_BUFFER_BOUND: usize = 4;
+const VERIFIER_BUFFER_BOUND: usize = 5;
 
 /// The chain verifier routes requests to either the checkpoint verifier or the
 /// block verifier, depending on the maximum checkpoint height.
@@ -62,12 +65,17 @@ const VERIFIER_BUFFER_BOUND: usize = 4;
 /// Block verification requests should be wrapped in a timeout, so that
 /// out-of-order and invalid requests do not hang indefinitely. See the [`chain`](`crate::chain`)
 /// module documentation for details.
-struct ChainVerifier<S>
+struct ChainVerifier<S, V>
 where
     S: Service<zs::Request, Response = zs::Response, Error = BoxError> + Send + Clone + 'static,
     S::Future: Send + 'static,
+    V: Service<transaction::Request, Response = transaction::Response, Error = BoxError>
+        + Send
+        + Clone
+        + 'static,
+    V::Future: Send + 'static,
 {
-    block: BlockVerifier<S>,
+    block: BlockVerifier<S, V>,
     checkpoint: CheckpointVerifier<S>,
     max_checkpoint_height: block::Height,
 }
@@ -81,10 +89,15 @@ pub enum VerifyChainError {
     Block(#[source] VerifyBlockError),
 }
 
-impl<S> Service<Arc<Block>> for ChainVerifier<S>
+impl<S, V> Service<Arc<Block>> for ChainVerifier<S, V>
 where
     S: Service<zs::Request, Response = zs::Response, Error = BoxError> + Send + Clone + 'static,
     S::Future: Send + 'static,
+    V: Service<transaction::Request, Response = transaction::Response, Error = BoxError>
+        + Send
+        + Clone
+        + 'static,
+    V::Future: Send + 'static,
 {
     type Response = block::Hash;
     type Error = VerifyChainError;
@@ -135,7 +148,7 @@ where
     }
 }
 
-/// Initialize a block verification service.
+/// Initialize block and transaction verification services.
 ///
 /// The consensus configuration is specified by `config`, and the Zcash network
 /// to verify blocks for is specified by `network`.
@@ -144,25 +157,42 @@ where
 /// checks. Blocks that pass semantic verification are submitted to the supplied
 /// `state_service` for contextual verification before being committed to the chain.
 ///
+/// The transaction verification service asynchronously performs semantic verification
+/// checks. Transactions that pass semantic verification return an `Ok` result to the caller.
+///
 /// This function should only be called once for a particular state service.
 ///
 /// Dropped requests are cancelled on a best-effort basis, but may continue to be processed.
 ///
 /// # Correctness
 ///
-/// Block verification requests should be wrapped in a timeout, so that
-/// out-of-order and invalid requests do not hang indefinitely. See the [`chain`](`crate::chain`)
-/// module documentation for details.
+/// Block and transaction verification requests should be wrapped in a timeout,
+/// so that out-of-order and invalid requests do not hang indefinitely.
+/// See the [`chain`](`crate::chain`) module documentation for details.
 #[instrument(skip(state_service))]
 pub async fn init<S>(
     config: Config,
     network: Network,
     mut state_service: S,
-) -> Buffer<BoxService<Arc<Block>, block::Hash, VerifyChainError>, Arc<Block>>
+) -> (
+    Buffer<BoxService<Arc<Block>, block::Hash, VerifyChainError>, Arc<Block>>,
+    Buffer<
+        BoxService<transaction::Request, transaction::Response, TransactionError>,
+        transaction::Request,
+    >,
+)
 where
     S: Service<zs::Request, Response = zs::Response, Error = BoxError> + Send + Clone + 'static,
     S::Future: Send + 'static,
 {
+    // transaction verification
+
+    let script = script::Verifier::new(state_service.clone());
+    let transaction = transaction::Verifier::new(network, script);
+    let transaction = Buffer::new(BoxService::new(transaction), VERIFIER_BUFFER_BOUND);
+
+    // block verification
+
     let list = CheckpointList::new(network);
 
     let max_checkpoint_height = if config.checkpoint_sync {
@@ -185,15 +215,15 @@ where
     };
     tracing::info!(?tip, ?max_checkpoint_height, "initializing chain verifier");
 
-    let block = BlockVerifier::new(network, state_service.clone());
+    let block = BlockVerifier::new(network, state_service.clone(), transaction.clone());
     let checkpoint = CheckpointVerifier::from_checkpoint_list(list, network, tip, state_service);
+    let chain = ChainVerifier {
+        block,
+        checkpoint,
+        max_checkpoint_height,
+    };
 
-    Buffer::new(
-        BoxService::new(ChainVerifier {
-            block,
-            checkpoint,
-            max_checkpoint_height,
-        }),
-        VERIFIER_BUFFER_BOUND,
-    )
+    let chain = Buffer::new(BoxService::new(chain), VERIFIER_BUFFER_BOUND);
+
+    (chain, transaction)
 }

zebra-consensus/src/chain/tests.rs

@@ -64,7 +64,7 @@ async fn verifiers_from_network(
         + 'static,
 ) {
     let state_service = zs::init_test(network);
-    let chain_verifier =
+    let (chain_verifier, _transaction_verifier) =
         crate::chain::init(Config::default(), network, state_service.clone()).await;
 
     (chain_verifier, state_service)
@@ -153,7 +153,8 @@ async fn verify_checkpoint(config: Config) -> Result<(), Report> {
 
     // Test that the chain::init function works. Most of the other tests use
     // init_from_verifiers.
-    let chain_verifier = super::init(config.clone(), network, zs::init_test(network)).await;
+    let (chain_verifier, _transaction_verifier) =
+        super::init(config.clone(), network, zs::init_test(network)).await;
 
     // Add a timeout layer
     let chain_verifier =

zebra-consensus/src/error.rs

@@ -90,15 +90,23 @@ pub enum TransactionError {
 }
 
 impl From<BoxError> for TransactionError {
-    fn from(err: BoxError) -> Self {
-        // TODO: handle redpallas Error?
+    fn from(mut err: BoxError) -> Self {
+        // TODO: handle redpallas::Error, ScriptInvalid, InvalidSignature
         match err.downcast::<zebra_chain::primitives::redjubjub::Error>() {
-            Ok(e) => TransactionError::RedJubjub(*e),
-            Err(e) => TransactionError::InternalDowncastError(format!(
-                "downcast to redjubjub::Error failed, original error: {:?}",
-                e
-            )),
+            Ok(e) => return TransactionError::RedJubjub(*e),
+            Err(e) => err = e,
         }
+
+        // buffered transaction verifier service error
+        match err.downcast::<TransactionError>() {
+            Ok(e) => return *e,
+            Err(e) => err = e,
+        }
+
+        TransactionError::InternalDowncastError(format!(
+            "downcast to known transaction error type failed, original error: {:?}",
+            err,
+        ))
     }
 }
 

zebra-consensus/src/transaction.rs

@@ -90,6 +90,10 @@ pub enum Request {
     },
 }
 
+/// The response type for the transaction verifier service.
+/// Responses identify the transaction that was verified.
+pub type Response = zebra_chain::transaction::Hash;
+
 impl Request {
     /// The transaction to verify that's in this request.
     pub fn transaction(&self) -> Arc<Transaction> {
@@ -127,7 +131,7 @@ where
     ZS: Service<zs::Request, Response = zs::Response, Error = BoxError> + Send + Clone + 'static,
     ZS::Future: Send + 'static,
 {
-    type Response = transaction::Hash;
+    type Response = Response;
     type Error = TransactionError;
     type Future =
         Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>> + Send + 'static>>;

zebra-consensus/src/transaction/tests.rs

@@ -406,7 +406,8 @@ async fn v4_transaction_with_transparent_transfer_is_rejected_by_the_script() {
     assert_eq!(
         result,
         Err(TransactionError::InternalDowncastError(
-            "downcast to redjubjub::Error failed, original error: ScriptInvalid".to_string()
+            "downcast to known transaction error type failed, original error: ScriptInvalid"
+                .to_string()
         ))
     );
 }
@@ -683,7 +684,7 @@ fn v4_with_unsigned_sprout_transfer_is_rejected() {
                 // TODO: Fix error downcast
                 // Err(TransactionError::Ed25519(ed25519::Error::InvalidSignature))
                 TransactionError::InternalDowncastError(
-                    "downcast to redjubjub::Error failed, original error: InvalidSignature"
+                    "downcast to known transaction error type failed, original error: InvalidSignature"
                         .to_string(),
                 )
             )

zebrad/src/commands/start.rs

@@ -55,7 +55,8 @@ impl StartCmd {
         let state = ServiceBuilder::new().buffer(20).service(state_service);
 
         info!("initializing verifiers");
-        let verifier = zebra_consensus::chain::init(
+        // TODO: use the transaction verifier to verify mempool transactions (#2637, #2606)
+        let (chain_verifier, _tx_verifier) = zebra_consensus::chain::init(
             config.consensus.clone(),
             config.network.network,
             state.clone(),
@@ -70,7 +71,11 @@ impl StartCmd {
         let inbound = ServiceBuilder::new()
             .load_shed()
             .buffer(20)
-            .service(Inbound::new(setup_rx, state.clone(), verifier.clone()));
+            .service(Inbound::new(
+                setup_rx,
+                state.clone(),
+                chain_verifier.clone(),
+            ));
 
         let (peer_set, address_book) =
             zebra_network::init(config.network.clone(), inbound, Some(best_tip_height)).await;
@@ -81,7 +86,7 @@ impl StartCmd {
         info!("initializing syncer");
         // TODO: use sync_length_receiver to activate the mempool (#2592)
         let (syncer, _sync_length_receiver) =
-            ChainSync::new(&config, peer_set.clone(), state, verifier);
+            ChainSync::new(&config, peer_set.clone(), state, chain_verifier);
 
         select! {
             result = syncer.sync().fuse() => result,