Patch concurrent update error

fendermint/vm/topdown/src/finality/null.rs

@@ -63,6 +63,17 @@ impl FinalityWithNull {
     /// Clear the cache and set the committed finality to the provided value
     pub fn reset(&self, finality: IPCParentFinality) -> Stm<()> {
         self.cached_data.write(SequentialKeyCache::sequential())?;
+
+        if let Some(p) = self.last_committed_finality.read()?.as_ref() {
+            if p.height > finality.height {
+                tracing::warn!(
+                    last = p.to_string(),
+                    next = finality.to_string(),
+                    "reset to a lower finality"
+                );
+            }
+        }
+
         self.last_committed_finality.write(Some(finality))
     }
 
@@ -71,6 +82,17 @@ impl FinalityWithNull {
         height: BlockHeight,
         maybe_payload: Option<ParentViewPayload>,
     ) -> StmResult<(), Error> {
+        if let Some(p) = self.last_committed_finality.read()?.as_ref() {
+            if p.height > height {
+                tracing::debug!(
+                    height,
+                    last_committed_height = p.height,
+                    "no need update parent view"
+                );
+                return Ok(());
+            }
+        }
+
         if let Some((block_hash, validator_changes, top_down_msgs)) = maybe_payload {
             self.parent_block_filled(height, block_hash, validator_changes, top_down_msgs)
         } else {

fendermint/vm/topdown/src/lib.rs

@@ -8,6 +8,8 @@ pub mod sync;
 
 pub mod convert;
 pub mod proxy;
+#[cfg(test)]
+mod test;
 mod toggle;
 
 use async_stm::Stm;

fendermint/vm/topdown/src/sync/mod.rs

@@ -6,7 +6,7 @@ mod syncer;
 mod tendermint;
 
 use crate::proxy::ParentQueryProxy;
-use crate::sync::syncer::LotusParentSyncer;
+pub(crate) use crate::sync::syncer::LotusParentSyncer;
 use crate::sync::tendermint::TendermintAwareSyncer;
 use crate::{CachedFinalityProvider, Config, IPCParentFinality, ParentFinalityProvider, Toggle};
 use anyhow::anyhow;

fendermint/vm/topdown/src/sync/syncer.rs

@@ -15,7 +15,7 @@ use std::sync::Arc;
 
 /// Parent syncer that constantly poll parent. This struct handles lotus null blocks and deferred
 /// execution. For ETH based parent, it should work out of the box as well.
-pub(crate) struct LotusParentSyncer<T, P> {
+pub struct LotusParentSyncer<T, P> {
     config: Config,
     parent_proxy: Arc<P>,
     provider: Arc<Toggle<CachedFinalityProvider<P>>>,

fendermint/vm/topdown/src/test.rs

@@ -0,0 +1,281 @@
+// Copyright 2022-2023 Protocol Labs
+// SPDX-License-Identifier: Apache-2.0, MIT
+
+use crate::finality::ParentViewPayload;
+use crate::proxy::ParentQueryProxy;
+use crate::sync::{LotusParentSyncer, ParentFinalityStateQuery};
+use crate::{
+    BlockHeight, CachedFinalityProvider, Config, IPCParentFinality, ParentFinalityProvider,
+    ParentViewProvider, SequentialKeyCache, Toggle, NULL_ROUND_ERR_MSG,
+};
+use anyhow::anyhow;
+use async_stm::atomically;
+use async_trait::async_trait;
+use ipc_provider::manager::{GetBlockHashResult, TopDownQueryPayload};
+use ipc_sdk::cross::CrossMsg;
+use ipc_sdk::staking::StakingChangeRequest;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::Arc;
+use std::time::Duration;
+use tokio::sync::Mutex;
+
+struct TestParentFinalityStateQuery {
+    latest_finality: IPCParentFinality,
+}
+
+impl ParentFinalityStateQuery for TestParentFinalityStateQuery {
+    fn get_latest_committed_finality(&self) -> anyhow::Result<Option<IPCParentFinality>> {
+        Ok(Some(self.latest_finality.clone()))
+    }
+}
+
+/// Creates a mock of a new parent blockchain view. The key is the height and the value is the
+/// block hash. If block hash is None, it means the current height is a null block.
+macro_rules! new_parent_blocks {
+        ($($key:expr => $val:expr),* ,) => (
+            hash_map!($($key => $val),*)
+        );
+        ($($key:expr => $val:expr),*) => ({
+            let mut map = SequentialKeyCache::sequential();
+            $( map.append($key, $val).unwrap(); )*
+            map
+        });
+    }
+
+struct TestParentProxy {
+    blocks: SequentialKeyCache<BlockHeight, Option<ParentViewPayload>>,
+    should_wait: Arc<AtomicBool>,
+    tx: tokio::sync::mpsc::Sender<u8>,
+}
+
+#[async_trait]
+impl ParentQueryProxy for TestParentProxy {
+    async fn get_chain_head_height(&self) -> anyhow::Result<BlockHeight> {
+        Ok(self.blocks.upper_bound().unwrap())
+    }
+
+    async fn get_genesis_epoch(&self) -> anyhow::Result<BlockHeight> {
+        Ok(self.blocks.lower_bound().unwrap() - 1)
+    }
+
+    async fn get_block_hash(&self, height: BlockHeight) -> anyhow::Result<GetBlockHashResult> {
+        let r = self.blocks.get_value(height).unwrap();
+        if r.is_none() {
+            return Err(anyhow!(NULL_ROUND_ERR_MSG));
+        }
+
+        for h in (self.blocks.lower_bound().unwrap()..height).rev() {
+            let v = self.blocks.get_value(h).unwrap();
+            if v.is_none() {
+                continue;
+            }
+            return Ok(GetBlockHashResult {
+                parent_block_hash: v.clone().unwrap().0,
+                block_hash: r.clone().unwrap().0,
+            });
+        }
+        panic!("invalid testing data")
+    }
+
+    async fn get_top_down_msgs(
+        &self,
+        height: BlockHeight,
+    ) -> anyhow::Result<TopDownQueryPayload<Vec<CrossMsg>>> {
+        while self.should_wait.load(Ordering::SeqCst) {
+            self.tx.send(0).await?;
+            tokio::time::sleep(Duration::from_millis(10)).await;
+        }
+
+        let r = self.blocks.get_value(height).cloned().unwrap();
+        if r.is_none() {
+            return Err(anyhow!(NULL_ROUND_ERR_MSG));
+        }
+        let r = r.unwrap();
+        Ok(TopDownQueryPayload {
+            value: r.2,
+            block_hash: r.0,
+        })
+    }
+
+    async fn get_validator_changes(
+        &self,
+        height: BlockHeight,
+    ) -> anyhow::Result<TopDownQueryPayload<Vec<StakingChangeRequest>>> {
+        let r = self.blocks.get_value(height).cloned().unwrap();
+        if r.is_none() {
+            return Err(anyhow!(NULL_ROUND_ERR_MSG));
+        }
+        let r = r.unwrap();
+        Ok(TopDownQueryPayload {
+            value: r.1,
+            block_hash: r.0,
+        })
+    }
+}
+
+async fn new_setup(
+    blocks: SequentialKeyCache<BlockHeight, Option<ParentViewPayload>>,
+    should_wait: Arc<AtomicBool>,
+    tx: tokio::sync::mpsc::Sender<u8>,
+) -> (
+    Arc<Toggle<CachedFinalityProvider<TestParentProxy>>>,
+    LotusParentSyncer<TestParentFinalityStateQuery, TestParentProxy>,
+) {
+    let config = Config {
+        chain_head_delay: 2,
+        polling_interval: Default::default(),
+        exponential_back_off: Default::default(),
+        exponential_retry_limit: 0,
+        max_proposal_range: Some(10),
+        max_cache_blocks: None,
+        proposal_delay: None,
+    };
+    let genesis_epoch = blocks.lower_bound().unwrap();
+    let proxy = Arc::new(TestParentProxy {
+        blocks,
+        should_wait,
+        tx,
+    });
+    let committed_finality = IPCParentFinality {
+        height: genesis_epoch,
+        block_hash: vec![0; 32],
+    };
+
+    let provider = CachedFinalityProvider::new(
+        config.clone(),
+        genesis_epoch,
+        Some(committed_finality.clone()),
+        proxy.clone(),
+    );
+    let provider = Arc::new(Toggle::enabled(provider));
+
+    let syncer = LotusParentSyncer::new(
+        config,
+        proxy,
+        provider.clone(),
+        Arc::new(TestParentFinalityStateQuery {
+            latest_finality: committed_finality,
+        }),
+    );
+
+    (provider, syncer)
+}
+
+/// This test case is for when pulling the next block, there is a new commit finality request
+/// and all cache is purged.
+#[tokio::test]
+async fn while_syncing_cache_purged() {
+    let parent_blocks = new_parent_blocks!(
+        100 => Some((vec![0; 32], vec![], vec![])),   // genesis block
+        101 => Some((vec![1; 32], vec![], vec![])),
+        102 => Some((vec![2; 32], vec![], vec![])),
+        103 => Some((vec![3; 32], vec![], vec![])),
+        104 => Some((vec![4; 32], vec![], vec![])),
+        105 => Some((vec![5; 32], vec![], vec![])),
+        106 => Some((vec![6; 32], vec![], vec![])),
+        107 => Some((vec![6; 32], vec![], vec![])),
+        108 => Some((vec![6; 32], vec![], vec![])),
+        109 => Some((vec![6; 32], vec![], vec![])),
+        110 => Some((vec![6; 32], vec![], vec![]))
+    );
+    let should_wait = Arc::new(AtomicBool::new(false));
+    let (tx, mut rx) = tokio::sync::mpsc::channel(10);
+
+    let (provider, mut syncer) = new_setup(parent_blocks, should_wait.clone(), tx).await;
+    syncer.sync().await.unwrap();
+    syncer.sync().await.unwrap();
+    syncer.sync().await.unwrap();
+    assert_eq!(
+        atomically(|| provider.next_proposal()).await,
+        Some(IPCParentFinality {
+            height: 101,
+            block_hash: vec![1; 32]
+        }),
+        "sanity check, make sure there is data in cache"
+    );
+
+    let syncer = Arc::new(Mutex::new(syncer));
+    // now make sure we are "waiting" for polling top down messages, like in real io
+    should_wait.store(true, Ordering::SeqCst);
+    let cloned_syncer = syncer.clone();
+    let handle = tokio::spawn(async move {
+        let mut syncer = cloned_syncer.lock().await;
+        syncer.sync().await.unwrap();
+    });
+
+    loop {
+        if (rx.recv().await).is_some() {
+            // syncer.sync is waiting, we mock a new proposal from peer
+            atomically(|| {
+                provider.set_new_finality(
+                    IPCParentFinality {
+                        height: 105,
+                        block_hash: vec![5; 32],
+                    },
+                    Some(IPCParentFinality {
+                        height: 100,
+                        block_hash: vec![0; 32],
+                    }),
+                )
+            })
+            .await;
+            should_wait.store(false, Ordering::SeqCst);
+            break;
+        }
+    }
+    handle.await.unwrap();
+    assert_eq!(
+        atomically(|| provider.next_proposal()).await,
+        None,
+        "cache should be evicted, so proposal should be made"
+    );
+
+    atomically(|| {
+        assert_eq!(Some(105), provider.latest_height()?);
+        assert_eq!(
+            Some(IPCParentFinality {
+                height: 105,
+                block_hash: vec![5; 32]
+            }),
+            provider.last_committed_finality()?
+        );
+        Ok(())
+    })
+    .await;
+
+    assert_eq!(
+        provider
+            .validator_changes_from(105, 105)
+            .await
+            .unwrap()
+            .len(),
+        0
+    );
+
+    // make sure syncer still works
+    let mut syncer = syncer.lock().await;
+    syncer.sync().await.unwrap();
+
+    atomically(|| {
+        assert_eq!(Some(106), provider.latest_height()?);
+        assert_eq!(
+            Some(IPCParentFinality {
+                height: 105,
+                block_hash: vec![5; 32]
+            }),
+            provider.last_committed_finality()?
+        );
+        Ok(())
+    })
+    .await;
+
+    syncer.sync().await.unwrap();
+    syncer.sync().await.unwrap();
+    assert_eq!(
+        atomically(|| provider.next_proposal()).await,
+        Some(IPCParentFinality {
+            height: 106,
+            block_hash: vec![6; 32]
+        }),
+    );
+}