feat(zebra-scan): Connect with zebrad (#7989)

* connect zebrad with zebra-scan

* remove unwrap

* use tokio::sleep

* fix the task handler

* Don't panic on an empty state

---------

Co-authored-by: teor <teor@riseup.net>

Cargo.lock

@@ -5806,6 +5806,8 @@ dependencies = [
  "rand 0.8.5",
  "serde",
  "tokio",
+ "tower",
+ "tracing",
  "zcash_client_backend",
  "zcash_note_encryption",
  "zcash_primitives",

zebra-scan/Cargo.toml

@@ -20,9 +20,14 @@ categories = ["cryptography::cryptocurrencies"]
 
 [dependencies]
 zebra-chain = { path = "../zebra-chain", version = "1.0.0-beta.31" }
+zebra-state = { path = "../zebra-state", version = "1.0.0-beta.31" }
 
+color-eyre = "0.6.2"
 indexmap = { version = "2.0.1", features = ["serde"] }
 serde = { version = "1.0.192", features = ["serde_derive"] }
+tokio = { version = "1.34.0", features = ["test-util"] }
+tower = "0.4.13"
+tracing = "0.1.39"
 
 [dev-dependencies]
 
@@ -30,13 +35,10 @@ zcash_client_backend = "0.10.0-rc.1"
 zcash_primitives = "0.13.0-rc.1"
 zcash_note_encryption = "0.4.0"
 
-color-eyre = { version = "0.6.2" }
 rand = "0.8.5"
 bls12_381 = "0.8.0"
 jubjub = "0.10.0"
 ff = "0.13.0"
 group = "0.13.0"
-tokio = { version = "1.34.0", features = ["test-util"] }
 
-zebra-state = { path = "../zebra-state" }
 zebra-test = { path = "../zebra-test" }

zebra-scan/src/lib.rs

@@ -5,7 +5,8 @@
 #![doc(html_root_url = "https://docs.rs/zebra_scan")]
 
 pub mod config;
-mod storage;
+pub mod scan;
+pub mod storage;
 
 #[cfg(test)]
 mod tests;

zebra-scan/src/scan.rs

@@ -0,0 +1,58 @@
+//! The scan task.
+
+use std::time::Duration;
+
+use color_eyre::{eyre::eyre, Report};
+use tower::{buffer::Buffer, util::BoxService, Service, ServiceExt};
+use tracing::info;
+
+use crate::storage::Storage;
+
+type State = Buffer<
+    BoxService<zebra_state::Request, zebra_state::Response, zebra_state::BoxError>,
+    zebra_state::Request,
+>;
+
+/// Wait a few seconds at startup so tip height is always `Some`.
+const INITIAL_WAIT: Duration = Duration::from_secs(10);
+
+/// The amount of time between checking and starting new scans.
+const CHECK_INTERVAL: Duration = Duration::from_secs(10);
+
+/// Start the scan task given state and storage.
+///
+/// - This function is dummy at the moment. It just makes sure we can read the storage and the state.
+/// - Modificatiuons here might have an impact in the `scan_task_starts` test.
+/// - Real scanning code functionality will be added in the future here.
+pub async fn start(mut state: State, storage: Storage) -> Result<(), Report> {
+    // We want to make sure the state has a tip height available before we start scanning.
+    tokio::time::sleep(INITIAL_WAIT).await;
+
+    loop {
+        // Make sure we can query the state
+        let request = state
+            .ready()
+            .await
+            .map_err(|e| eyre!(e))?
+            .call(zebra_state::Request::Tip)
+            .await
+            .map_err(|e| eyre!(e));
+
+        let tip = match request? {
+            zebra_state::Response::Tip(tip) => tip,
+            _ => unreachable!("unmatched response to a state::Tip request"),
+        };
+
+        // Read keys from the storage
+        let available_keys = storage.get_sapling_keys();
+
+        for key in available_keys {
+            info!(
+                "Scanning the blockchain for key {} from block 1 to {:?}",
+                key.0, tip,
+            );
+        }
+
+        tokio::time::sleep(CHECK_INTERVAL).await;
+    }
+}

zebra-scan/src/storage.rs

@@ -52,3 +52,9 @@ impl Storage {
         self.sapling_keys.clone()
     }
 }
+
+impl Default for Storage {
+    fn default() -> Self {
+        Self::new()
+    }
+}

zebrad/src/commands/start.rs

@@ -195,7 +195,7 @@ impl StartCmd {
             block_download_peer_set: peer_set.clone(),
             block_verifier: block_verifier_router.clone(),
             mempool: mempool.clone(),
-            state,
+            state: state.clone(),
             latest_chain_tip: latest_chain_tip.clone(),
         };
         setup_tx
@@ -262,6 +262,7 @@ impl StartCmd {
             .in_current_span(),
         );
 
+        // Spawn never ending end of support task.
         info!("spawning end of support checking task");
         let end_of_support_task_handle = tokio::spawn(
             sync::end_of_support::start(config.network.network, latest_chain_tip).in_current_span(),
@@ -285,6 +286,22 @@ impl StartCmd {
         info!("spawning syncer task");
         let syncer_task_handle = tokio::spawn(syncer.sync().in_current_span());
 
+        #[cfg(feature = "zebra-scan")]
+        // Spawn never ending scan task.
+        let scan_task_handle = {
+            info!("spawning zebra_scanner");
+            let mut storage = zebra_scan::storage::Storage::new();
+            for (key, birthday) in config.shielded_scan.sapling_keys_to_scan.iter() {
+                storage.add_sapling_key(key.clone(), Some(zebra_chain::block::Height(*birthday)));
+            }
+
+            tokio::spawn(zebra_scan::scan::start(state, storage).in_current_span())
+        };
+        #[cfg(not(feature = "zebra-scan"))]
+        // Spawn a dummy scan task which doesn't do anything and never finishes.
+        let scan_task_handle: tokio::task::JoinHandle<Result<(), Report>> =
+            tokio::spawn(std::future::pending().in_current_span());
+
         info!("spawned initial Zebra tasks");
 
         // TODO: put tasks into an ongoing FuturesUnordered and a startup FuturesUnordered?
@@ -299,6 +316,7 @@ impl StartCmd {
         pin!(tx_gossip_task_handle);
         pin!(progress_task_handle);
         pin!(end_of_support_task_handle);
+        pin!(scan_task_handle);
 
         // startup tasks
         let BackgroundTaskHandles {
@@ -385,6 +403,10 @@ impl StartCmd {
                     exit_when_task_finishes = false;
                     Ok(())
                 }
+
+                scan_result = &mut scan_task_handle => scan_result
+                    .expect("unexpected panic in the scan task")
+                    .map(|_| info!("scan task exited")),
             };
 
             // Stop Zebra if a task finished and returned an error,
@@ -410,6 +432,7 @@ impl StartCmd {
         tx_gossip_task_handle.abort();
         progress_task_handle.abort();
         end_of_support_task_handle.abort();
+        scan_task_handle.abort();
 
         // startup tasks
         state_checkpoint_verify_handle.abort();

zebrad/tests/acceptance.rs

@@ -2799,3 +2799,46 @@ async fn fully_synced_rpc_z_getsubtreesbyindex_snapshot_test() -> Result<()> {
 
     Ok(())
 }
+
+#[cfg(feature = "zebra-scan")]
+/// Test that the scanner gets started when the node starts.
+#[tokio::test]
+async fn scan_task_starts() -> Result<()> {
+    use indexmap::IndexMap;
+
+    const ZECPAGES_VIEWING_KEY: &str = "zxviews1q0duytgcqqqqpqre26wkl45gvwwwd706xw608hucmvfalr759ejwf7qshjf5r9aa7323zulvz6plhttp5mltqcgs9t039cx2d09mgq05ts63n8u35hyv6h9nc9ctqqtue2u7cer2mqegunuulq2luhq3ywjcz35yyljewa4mgkgjzyfwh6fr6jd0dzd44ghk0nxdv2hnv4j5nxfwv24rwdmgllhe0p8568sgqt9ckt02v2kxf5ahtql6s0ltjpkckw8gtymxtxuu9gcr0swvz";
+
+    let _init_guard = zebra_test::init();
+
+    let mut config = default_test_config(Mainnet)?;
+    let mut keys = IndexMap::new();
+    keys.insert(ZECPAGES_VIEWING_KEY.to_string(), 1);
+    config.shielded_scan.sapling_keys_to_scan = keys;
+
+    let testdir = testdir()?.with_config(&mut config)?;
+    let testdir = &testdir;
+
+    let mut child = testdir.spawn_child(args!["start"])?;
+
+    // Run the program and kill it after the scanner starts and the first scanning is done.
+    std::thread::sleep(LAUNCH_DELAY * 2);
+    child.kill(false)?;
+
+    // Check that scan task started and the first scanning is done.
+    let output = child.wait_with_output()?;
+
+    output.stdout_line_contains("spawning zebra_scanner")?;
+    output.stdout_line_contains(
+        format!(
+            "Scanning the blockchain for key {} from block 1 to",
+            ZECPAGES_VIEWING_KEY
+        )
+        .as_str(),
+    )?;
+
+    // Make sure the command was killed
+    output.assert_was_killed()?;
+    output.assert_failure()?;
+
+    Ok(())
+}