keep track of blockchain context validity internally.

consensus/Cargo.toml

@@ -45,6 +45,7 @@ cryptonight-cuprate = {path = "../cryptonight"}
 
 rayon = "1"
 tokio = "1"
+tokio-util = "0.7"
 
 # used in binaries
 monero-wire = {path="../net/monero-wire", optional = true}

consensus/src/block.rs

@@ -122,11 +122,14 @@ where
     Tx: Service<VerifyTxRequest, Response = VerifyTxResponse, Error = ConsensusError>,
 {
     tracing::debug!("getting blockchain context");
-    let context = context_svc
+    let checked_context = context_svc
         .oneshot(BlockChainContextRequest)
         .await
         .map_err(Into::<ConsensusError>::into)?;
 
+    // TODO: should we unwrap here, we did just get the data so it should be ok.
+    let context = checked_context.blockchain_context().unwrap();
+
     tracing::debug!("got blockchain context: {:?}", context);
 
     let block_weight = block.miner_tx.weight() + txs.iter().map(|tx| tx.tx_weight).sum::<usize>();
@@ -208,11 +211,14 @@ where
     Tx: Service<VerifyTxRequest, Response = VerifyTxResponse, Error = ConsensusError>,
 {
     tracing::debug!("getting blockchain context");
-    let context = context_svc
+    let checked_context = context_svc
         .oneshot(BlockChainContextRequest)
         .await
         .map_err(Into::<ConsensusError>::into)?;
 
+    // TODO: should we unwrap here, we did just get the data so it should be ok.
+    let context = checked_context.blockchain_context().unwrap();
+
     tracing::debug!("got blockchain context: {:?}", context);
 
     // TODO: reorder these tests so we do the cheap tests first.

consensus/src/context.rs

@@ -16,13 +16,17 @@ use std::{
 
 use futures::FutureExt;
 use tokio::sync::RwLock;
+use tokio_util::sync::CancellationToken;
 use tower::{Service, ServiceExt};
 
 use crate::{helper::current_time, ConsensusError, Database, DatabaseRequest, DatabaseResponse};
 
-pub mod difficulty;
-pub mod hardforks;
-pub mod weight;
+mod difficulty;
+mod hardforks;
+mod weight;
+
+#[cfg(test)]
+mod tests;
 
 pub use difficulty::DifficultyCacheConfig;
 pub use hardforks::{HardFork, HardForkConfig};
@@ -31,9 +35,9 @@ pub use weight::BlockWeightsCacheConfig;
 const BLOCKCHAIN_TIMESTAMP_CHECK_WINDOW: u64 = 60;
 
 pub struct ContextConfig {
-    hard_fork_cfg: HardForkConfig,
-    difficulty_cfg: DifficultyCacheConfig,
-    weights_config: BlockWeightsCacheConfig,
+    pub hard_fork_cfg: HardForkConfig,
+    pub difficulty_cfg: DifficultyCacheConfig,
+    pub weights_config: BlockWeightsCacheConfig,
 }
 
 impl ContextConfig {
@@ -114,6 +118,7 @@ where
     let context_svc = BlockChainContextService {
         internal_blockchain_context: Arc::new(
             InternalBlockChainContext {
+                current_validity_token: CancellationToken::new(),
                 difficulty_cache: difficulty_cache_handle.await.unwrap()?,
                 weight_cache: weight_cache_handle.await.unwrap()?,
                 hardfork_state: hardfork_state_handle.await.unwrap()?,
@@ -130,8 +135,10 @@ where
     Ok((context_svc_update.clone(), context_svc_update))
 }
 
+/// Raw blockchain context, gotten from [`BlockChainContext`]. This data may turn invalid so is not ok to keep
+/// around. You should keep around [`BlockChainContext`] instead.
 #[derive(Debug, Clone, Copy)]
-pub struct BlockChainContext {
+pub struct RawBlockChainContext {
     /// The next blocks difficulty.
     pub next_difficulty: u128,
     /// The current cumulative difficulty.
@@ -156,7 +163,7 @@ pub struct BlockChainContext {
     pub current_hard_fork: HardFork,
 }
 
-impl BlockChainContext {
+impl RawBlockChainContext {
     /// Returns the timestamp the should be used when checking locked outputs.
     ///
     /// https://cuprate.github.io/monero-book/consensus_rules/transactions/unlock_time.html#getting-the-current-time
@@ -197,11 +204,44 @@ impl BlockChainContext {
     }
 }
 
+/// Blockchain context which keeps a token of validity so users will know when the data is no longer valid.
+#[derive(Debug, Clone)]
+pub struct BlockChainContext {
+    /// A token representing this data's validity.
+    validity_token: CancellationToken,
+    /// The actual block chain context.
+    raw: RawBlockChainContext,
+}
+
+#[derive(Debug, Clone, Copy, thiserror::Error)]
+#[error("data is no longer valid")]
+pub struct DataNoLongerValid;
+
+impl BlockChainContext {
+    /// Checks if the data is still valid.
+    pub fn is_still_valid(&self) -> bool {
+        !self.validity_token.is_cancelled()
+    }
+
+    /// Checks if the data is valid returning an Err if not and a reference to the blockchain context if
+    /// it is.
+    pub fn blockchain_context(&self) -> Result<RawBlockChainContext, DataNoLongerValid> {
+        if !self.is_still_valid() {
+            return Err(DataNoLongerValid);
+        }
+        Ok(self.raw)
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct BlockChainContextRequest;
 
 #[derive(Clone)]
 struct InternalBlockChainContext {
+    /// A token used to invalidate previous contexts when a new
+    /// block is added to the chain.
+    current_validity_token: CancellationToken,
+
     difficulty_cache: difficulty::DifficultyCache,
     weight_cache: weight::BlockWeightsCache,
     hardfork_state: hardforks::HardForkState,
@@ -233,6 +273,7 @@ impl Service<BlockChainContextRequest> for BlockChainContextService {
             let internal_blockchain_context_lock = internal_blockchain_context.read().await;
 
             let InternalBlockChainContext {
+                current_validity_token,
                 difficulty_cache,
                 weight_cache,
                 hardfork_state,
@@ -244,18 +285,24 @@ impl Service<BlockChainContextRequest> for BlockChainContextService {
             let current_hf = hardfork_state.current_hardfork();
 
             Ok(BlockChainContext {
+                validity_token: current_validity_token.child_token(),
+                raw: RawBlockChainContext {
                     next_difficulty: difficulty_cache.next_difficulty(&current_hf),
                     cumulative_difficulty: difficulty_cache.cumulative_difficulty(),
-                effective_median_weight: weight_cache.effective_median_block_weight(&current_hf),
+                    effective_median_weight: weight_cache
+                        .effective_median_block_weight(&current_hf),
                     median_long_term_weight: weight_cache.median_long_term_weight(),
-                median_weight_for_block_reward: weight_cache.median_for_block_reward(&current_hf),
+                    median_weight_for_block_reward: weight_cache
+                        .median_for_block_reward(&current_hf),
                     already_generated_coins: *already_generated_coins,
                     top_block_timestamp: difficulty_cache.top_block_timestamp(),
-                median_block_timestamp: difficulty_cache
-                    .median_timestamp(usize::try_from(BLOCKCHAIN_TIMESTAMP_CHECK_WINDOW).unwrap()),
+                    median_block_timestamp: difficulty_cache.median_timestamp(
+                        usize::try_from(BLOCKCHAIN_TIMESTAMP_CHECK_WINDOW).unwrap(),
+                    ),
                     chain_height: *chain_height,
                     top_hash: *top_block_hash,
                     current_hard_fork: current_hf,
+                },
             })
         }
         .boxed()
@@ -291,6 +338,7 @@ impl tower::Service<UpdateBlockchainCacheRequest> for BlockChainContextService {
             let mut internal_blockchain_context_lock = internal_blockchain_context.write().await;
 
             let InternalBlockChainContext {
+                current_validity_token,
                 difficulty_cache,
                 weight_cache,
                 hardfork_state,
@@ -299,11 +347,14 @@ impl tower::Service<UpdateBlockchainCacheRequest> for BlockChainContextService {
                 already_generated_coins,
             } = internal_blockchain_context_lock.deref_mut();
 
+            // Cancel the validity token and replace it with a new one.
+            std::mem::replace(current_validity_token, CancellationToken::new()).cancel();
+
             difficulty_cache.new_block(new.height, new.timestamp, new.cumulative_difficulty);
 
             weight_cache.new_block(new.height, new.weight, new.long_term_weight);
 
-            hardfork_state.new_block(new.vote, new.height).await?;
+            hardfork_state.new_block(new.vote, new.height);
 
             *chain_height = new.height + 1;
             *top_block_hash = new.new_top_hash;

consensus/src/context/difficulty.rs

@@ -8,7 +8,7 @@ use crate::{
 };
 
 #[cfg(test)]
-mod tests;
+pub(super) mod tests;
 
 /// The amount of blocks we account for to calculate difficulty
 const DIFFICULTY_WINDOW: usize = 720;
@@ -69,22 +69,6 @@ pub struct DifficultyCache {
 }
 
 impl DifficultyCache {
-    pub async fn init<D: Database + Clone>(
-        config: DifficultyCacheConfig,
-        mut database: D,
-    ) -> Result<Self, ConsensusError> {
-        let DatabaseResponse::ChainHeight(chain_height, _) = database
-            .ready()
-            .await?
-            .call(DatabaseRequest::ChainHeight)
-            .await?
-        else {
-            panic!("Database sent incorrect response")
-        };
-
-        DifficultyCache::init_from_chain_height(chain_height, config, database).await
-    }
-
     #[instrument(name = "init_difficulty_cache", level = "info", skip(database, config))]
     pub async fn init_from_chain_height<D: Database + Clone>(
         chain_height: u64,

consensus/src/context/difficulty/tests.rs

@@ -11,7 +11,7 @@ const TEST_LAG: usize = 2;
 
 const TEST_TOTAL_ACCOUNTED_BLOCKS: usize = TEST_WINDOW + TEST_LAG;
 
-const TEST_DIFFICULTY_CONFIG: DifficultyCacheConfig =
+pub const TEST_DIFFICULTY_CONFIG: DifficultyCacheConfig =
     DifficultyCacheConfig::new(TEST_WINDOW, TEST_CUT, TEST_LAG);
 
 #[tokio::test]
@@ -21,7 +21,8 @@ async fn first_3_blocks_fixed_difficulty() -> Result<(), tower::BoxError> {
     db_builder.add_block(genesis);
 
     let mut difficulty_cache =
-        DifficultyCache::init(TEST_DIFFICULTY_CONFIG, db_builder.finish()).await?;
+        DifficultyCache::init_from_chain_height(1, TEST_DIFFICULTY_CONFIG, db_builder.finish())
+            .await?;
 
     for height in 1..3 {
         assert_eq!(difficulty_cache.next_difficulty(&HardFork::V1), 1);
@@ -35,7 +36,9 @@ async fn genesis_block_skipped() -> Result<(), tower::BoxError> {
     let mut db_builder = DummyDatabaseBuilder::default();
     let genesis = DummyBlockExtendedHeader::default().with_difficulty_info(0, 1);
     db_builder.add_block(genesis);
-    let diff_cache = DifficultyCache::init(TEST_DIFFICULTY_CONFIG, db_builder.finish()).await?;
+    let diff_cache =
+        DifficultyCache::init_from_chain_height(1, TEST_DIFFICULTY_CONFIG, db_builder.finish())
+            .await?;
     assert!(diff_cache.cumulative_difficulties.is_empty());
     assert!(diff_cache.timestamps.is_empty());
     Ok(())

consensus/src/context/hardforks.rs

@@ -12,7 +12,7 @@ use tracing::instrument;
 use crate::{ConsensusError, Database, DatabaseRequest, DatabaseResponse};
 
 #[cfg(test)]
-mod tests;
+pub(super) mod tests;
 
 // https://cuprate.github.io/monero-docs/consensus_rules/hardforks.html#accepting-a-fork
 const DEFAULT_WINDOW_SIZE: u64 = 10080; // supermajority window check length - a week
@@ -263,24 +263,6 @@ pub struct HardForkState {
 }
 
 impl HardForkState {
-    pub async fn init<D: Database + Clone>(
-        config: HardForkConfig,
-        mut database: D,
-    ) -> Result<Self, ConsensusError> {
-        let DatabaseResponse::ChainHeight(chain_height, _) = database
-            .ready()
-            .await?
-            .call(DatabaseRequest::ChainHeight)
-            .await?
-        else {
-            panic!("Database sent incorrect response")
-        };
-
-        let hfs = HardForkState::init_from_chain_height(chain_height, config, database).await?;
-
-        Ok(hfs)
-    }
-
     #[instrument(name = "init_hardfork_state", skip(config, database), level = "info")]
     pub async fn init_from_chain_height<D: Database + Clone>(
         chain_height: u64,
@@ -336,7 +318,7 @@ impl HardForkState {
         Ok(hfs)
     }
 
-    pub async fn new_block(&mut self, vote: HardFork, height: u64) -> Result<(), ConsensusError> {
+    pub fn new_block(&mut self, vote: HardFork, height: u64) {
         assert_eq!(self.last_height + 1, height);
         self.last_height += 1;
 
@@ -353,7 +335,6 @@ impl HardForkState {
         }
 
         self.check_set_new_hf();
-        Ok(())
     }
 
     /// Checks if the next hard-fork should be activated and activates it if it should.

consensus/src/context/hardforks/tests.rs

@@ -26,7 +26,7 @@ const TEST_HFS: [HFInfo; NUMB_OF_HARD_FORKS] = [
     HFInfo::new(150, 0),
 ];
 
-const TEST_HARD_FORK_CONFIG: HardForkConfig = HardForkConfig {
+pub const TEST_HARD_FORK_CONFIG: HardForkConfig = HardForkConfig {
     window: TEST_WINDOW_SIZE,
     forks: TEST_HFS,
 };
@@ -62,7 +62,11 @@ async fn hard_fork_set_depends_on_top_block() {
         DummyBlockExtendedHeader::default().with_hard_fork_info(HardFork::V14, HardFork::V16),
     );
 
-    let state = HardForkState::init(TEST_HARD_FORK_CONFIG, db_builder.finish())
+    let state = HardForkState::init_from_chain_height(
+        TEST_WINDOW_SIZE + 1,
+        TEST_HARD_FORK_CONFIG,
+        db_builder.finish(),
+    )
     .await
     .unwrap();
 

consensus/src/context/tests.rs

@@ -0,0 +1,74 @@
+use proptest::strategy::ValueTree;
+use proptest::{strategy::Strategy, test_runner::TestRunner};
+use tower::ServiceExt;
+
+use super::{
+    difficulty::tests::TEST_DIFFICULTY_CONFIG, hardforks::tests::TEST_HARD_FORK_CONFIG,
+    initialize_blockchain_context, weight::tests::TEST_WEIGHT_CONFIG, BlockChainContextRequest,
+    ContextConfig, UpdateBlockchainCacheRequest,
+};
+use crate::{test_utils::mock_db::*, HardFork};
+
+const TEST_CONTEXT_CONFIG: ContextConfig = ContextConfig {
+    hard_fork_cfg: TEST_HARD_FORK_CONFIG,
+    difficulty_cfg: TEST_DIFFICULTY_CONFIG,
+    weights_config: TEST_WEIGHT_CONFIG,
+};
+
+#[tokio::test]
+async fn context_invalidated_on_new_block() -> Result<(), tower::BoxError> {
+    const BLOCKCHAIN_HEIGHT: u64 = 6000;
+
+    let mut runner = TestRunner::default();
+    let db = arb_dummy_database(BLOCKCHAIN_HEIGHT.try_into().unwrap())
+        .new_tree(&mut runner)
+        .unwrap()
+        .current();
+
+    let (ctx_svc, updater) = initialize_blockchain_context(TEST_CONTEXT_CONFIG, db).await?;
+
+    let context = ctx_svc.oneshot(BlockChainContextRequest).await?;
+
+    assert!(context.is_still_valid());
+    assert!(context.is_still_valid());
+    assert!(context.is_still_valid());
+
+    updater
+        .oneshot(UpdateBlockchainCacheRequest {
+            new_top_hash: [0; 32],
+            height: BLOCKCHAIN_HEIGHT,
+            timestamp: 0,
+            weight: 0,
+            long_term_weight: 0,
+            generated_coins: 0,
+            vote: HardFork::V1,
+            cumulative_difficulty: 0,
+        })
+        .await?;
+
+    assert!(!context.is_still_valid());
+
+    Ok(())
+}
+
+#[tokio::test]
+async fn context_height_correct() -> Result<(), tower::BoxError> {
+    const BLOCKCHAIN_HEIGHT: u64 = 6000;
+
+    let mut runner = TestRunner::default();
+    let db = arb_dummy_database(BLOCKCHAIN_HEIGHT.try_into().unwrap())
+        .new_tree(&mut runner)
+        .unwrap()
+        .current();
+
+    let (ctx_svc, _) = initialize_blockchain_context(TEST_CONTEXT_CONFIG, db).await?;
+
+    let context = ctx_svc.oneshot(BlockChainContextRequest).await?;
+
+    assert_eq!(
+        context.blockchain_context().unwrap().chain_height,
+        BLOCKCHAIN_HEIGHT
+    );
+
+    Ok(())
+}

consensus/src/context/weight.rs

@@ -12,7 +12,6 @@ use std::{
     ops::Range,
 };
 
-use monero_serai::{block::Block, transaction::Transaction};
 use rayon::prelude::*;
 use tower::ServiceExt;
 use tracing::instrument;
@@ -22,7 +21,7 @@ use crate::{
 };
 
 #[cfg(test)]
-mod tests;
+pub(super) mod tests;
 
 const PENALTY_FREE_ZONE_1: usize = 20000;
 const PENALTY_FREE_ZONE_2: usize = 60000;
@@ -31,16 +30,6 @@ const PENALTY_FREE_ZONE_5: usize = 300000;
 const SHORT_TERM_WINDOW: u64 = 100;
 const LONG_TERM_WINDOW: u64 = 100000;
 
-/// Calculates the blocks weight.
-///
-/// https://cuprate.github.io/monero-book/consensus_rules/blocks/weight_limit.html#blocks-weight
-pub fn block_weight(block: &Block, txs: &[Transaction]) -> usize {
-    txs.iter()
-        .chain([&block.miner_tx])
-        .map(|tx| tx.weight())
-        .sum()
-}
-
 /// Returns the penalty free zone
 ///
 /// https://cuprate.github.io/monero-book/consensus_rules/blocks/weight_limit.html#penalty-free-zone
@@ -94,23 +83,6 @@ pub struct BlockWeightsCache {
 }
 
 impl BlockWeightsCache {
-    /// Initialize the [`BlockWeightsCache`] at the the height of the database.
-    pub async fn init<D: Database + Clone>(
-        config: BlockWeightsCacheConfig,
-        mut database: D,
-    ) -> Result<Self, ConsensusError> {
-        let DatabaseResponse::ChainHeight(chain_height, _) = database
-            .ready()
-            .await?
-            .call(DatabaseRequest::ChainHeight)
-            .await?
-        else {
-            panic!("Database sent incorrect response!");
-        };
-
-        Self::init_from_chain_height(chain_height, config, database).await
-    }
-
     /// Initialize the [`BlockWeightsCache`] at the the given chain height.
     #[instrument(name = "init_weight_cache", level = "info", skip(database, config))]
     pub async fn init_from_chain_height<D: Database + Clone>(

consensus/src/context/weight/tests.rs

@@ -1,7 +1,7 @@
 use super::{BlockWeightsCache, BlockWeightsCacheConfig};
 use crate::test_utils::mock_db::*;
 
-const TEST_WEIGHT_CONFIG: BlockWeightsCacheConfig = BlockWeightsCacheConfig::new(100, 5000);
+pub const TEST_WEIGHT_CONFIG: BlockWeightsCacheConfig = BlockWeightsCacheConfig::new(100, 5000);
 
 #[tokio::test]
 async fn blocks_out_of_window_not_counted() -> Result<(), tower::BoxError> {
@@ -11,7 +11,9 @@ async fn blocks_out_of_window_not_counted() -> Result<(), tower::BoxError> {
         db_builder.add_block(block);
     }
 
-    let mut weight_cache = BlockWeightsCache::init(TEST_WEIGHT_CONFIG, db_builder.finish()).await?;
+    let mut weight_cache =
+        BlockWeightsCache::init_from_chain_height(5000, TEST_WEIGHT_CONFIG, db_builder.finish())
+            .await?;
     assert_eq!(weight_cache.median_long_term_weight(), 2500);
     assert_eq!(weight_cache.median_short_term_weight(), 4950);
 
@@ -33,7 +35,9 @@ async fn weight_cache_calculates_correct_median() -> Result<(), tower::BoxError>
     let block = DummyBlockExtendedHeader::default().with_weight_into(0, 0);
     db_builder.add_block(block);
 
-    let mut weight_cache = BlockWeightsCache::init(TEST_WEIGHT_CONFIG, db_builder.finish()).await?;
+    let mut weight_cache =
+        BlockWeightsCache::init_from_chain_height(1, TEST_WEIGHT_CONFIG, db_builder.finish())
+            .await?;
 
     for height in 1..=100 {
         weight_cache.new_block(height as u64, height, height);

consensus/src/test_utils/mock_db.rs

@@ -1,4 +1,3 @@
-use futures::FutureExt;
 use std::{
     future::Future,
     pin::Pin,
@@ -6,20 +5,53 @@ use std::{
     task::{Context, Poll},
 };
 
-use cuprate_common::BlockID;
+use futures::FutureExt;
+use proptest::{
+    arbitrary::{any, any_with},
+    prop_compose,
+    sample::size_range,
+    strategy::Strategy,
+};
+use proptest_derive::Arbitrary;
 use tower::{BoxError, Service};
 
+use cuprate_common::BlockID;
+
 use crate::{DatabaseRequest, DatabaseResponse, ExtendedBlockHeader, HardFork};
 
-#[derive(Default, Debug, Clone, Copy)]
+prop_compose! {
+    /// Generates an arbitrary full [`DummyDatabase`], it is not safe to do consensus checks on the returned database
+    /// but is ok for testing certain parts of the code with.
+    pub fn arb_dummy_database(height: usize)
+                   (
+                       mut blocks in any_with::<Vec<DummyBlockExtendedHeader>>(size_range(height).lift())
+                   ) -> DummyDatabase {
+        let mut builder = DummyDatabaseBuilder::default();
+
+        blocks.sort_by(|a, b| a.cumulative_difficulty.cmp(&b.cumulative_difficulty));
+
+        for block in blocks {
+            builder.add_block(block);
+        }
+        builder.finish()
+    }
+}
+
+#[derive(Default, Debug, Clone, Copy, Arbitrary)]
 pub struct DummyBlockExtendedHeader {
+    #[proptest(strategy = "any::<HardFork>().prop_map(Some)")]
     pub version: Option<HardFork>,
+    #[proptest(strategy = "any::<HardFork>().prop_map(Some)")]
     pub vote: Option<HardFork>,
 
+    #[proptest(strategy = "any::<u64>().prop_map(Some)")]
     pub timestamp: Option<u64>,
+    #[proptest(strategy = "any::<u128>().prop_map(|x| Some(x % u128::from(u64::MAX)))")]
     pub cumulative_difficulty: Option<u128>,
 
+    #[proptest(strategy = "any::<usize>().prop_map(|x| Some(x % 100_000_000))")]
     pub block_weight: Option<usize>,
+    #[proptest(strategy = "any::<usize>().prop_map(|x| Some(x % 100_000_000))")]
     pub long_term_weight: Option<usize>,
 }
 
@@ -85,7 +117,7 @@ impl DummyDatabaseBuilder {
     }
 }
 
-#[derive(Clone)]
+#[derive(Clone, Debug)]
 pub struct DummyDatabase {
     blocks: Arc<RwLock<Vec<DummyBlockExtendedHeader>>>,
 }