be4e261e74
## Overview This rather extensive PR achieves two primary goals: 1. Uses the finalized/justified checkpoints of fork choice (FC), rather than that of the head state. 2. Refactors fork choice, block production and block processing to `async` functions. Additionally, it achieves: - Concurrent forkchoice updates to the EL and cache pruning after a new head is selected. - Concurrent "block packing" (attestations, etc) and execution payload retrieval during block production. - Concurrent per-block-processing and execution payload verification during block processing. - The `Arc`-ification of `SignedBeaconBlock` during block processing (it's never mutated, so why not?): - I had to do this to deal with sending blocks into spawned tasks. - Previously we were cloning the beacon block at least 2 times during each block processing, these clones are either removed or turned into cheaper `Arc` clones. - We were also `Box`-ing and un-`Box`-ing beacon blocks as they moved throughout the networking crate. This is not a big deal, but it's nice to avoid shifting things between the stack and heap. - Avoids cloning *all the blocks* in *every chain segment* during sync. - It also has the potential to clean up our code where we need to pass an *owned* block around so we can send it back in the case of an error (I didn't do much of this, my PR is already big enough 😅) - The `BeaconChain::HeadSafetyStatus` struct was removed. It was an old relic from prior merge specs. For motivation for this change, see https://github.com/sigp/lighthouse/pull/3244#issuecomment-1160963273 ## Changes to `canonical_head` and `fork_choice` Previously, the `BeaconChain` had two separate fields: ``` canonical_head: RwLock<Snapshot>, fork_choice: RwLock<BeaconForkChoice> ``` Now, we have grouped these values under a single struct: ``` canonical_head: CanonicalHead { cached_head: RwLock<Arc<Snapshot>>, fork_choice: RwLock<BeaconForkChoice> } ``` Apart from ergonomics, the only *actual* change here is wrapping the canonical head snapshot in an `Arc`. This means that we no longer need to hold the `cached_head` (`canonical_head`, in old terms) lock when we want to pull some values from it. This was done to avoid deadlock risks by preventing functions from acquiring (and holding) the `cached_head` and `fork_choice` locks simultaneously. ## Breaking Changes ### The `state` (root) field in the `finalized_checkpoint` SSE event Consider the scenario where epoch `n` is just finalized, but `start_slot(n)` is skipped. There are two state roots we might in the `finalized_checkpoint` SSE event: 1. The state root of the finalized block, which is `get_block(finalized_checkpoint.root).state_root`. 4. The state root at slot of `start_slot(n)`, which would be the state from (1), but "skipped forward" through any skip slots. Previously, Lighthouse would choose (2). However, we can see that when [Teku generates that event](de2b2801c8/data/beaconrestapi/src/main/java/tech/pegasys/teku/beaconrestapi/handlers/v1/events/EventSubscriptionManager.java (L171-L182)
) it uses [`getStateRootFromBlockRoot`](de2b2801c8/data/provider/src/main/java/tech/pegasys/teku/api/ChainDataProvider.java (L336-L341)
) which uses (1). I have switched Lighthouse from (2) to (1). I think it's a somewhat arbitrary choice between the two, where (1) is easier to compute and is consistent with Teku. ## Notes for Reviewers I've renamed `BeaconChain::fork_choice` to `BeaconChain::recompute_head`. Doing this helped ensure I broke all previous uses of fork choice and I also find it more descriptive. It describes an action and can't be confused with trying to get a reference to the `ForkChoice` struct. I've changed the ordering of SSE events when a block is received. It used to be `[block, finalized, head]` and now it's `[block, head, finalized]`. It was easier this way and I don't think we were making any promises about SSE event ordering so it's not "breaking". I've made it so fork choice will run when it's first constructed. I did this because I wanted to have a cached version of the last call to `get_head`. Ensuring `get_head` has been run *at least once* means that the cached values doesn't need to wrapped in an `Option`. This was fairly simple, it just involved passing a `slot` to the constructor so it knows *when* it's being run. When loading a fork choice from the store and a slot clock isn't handy I've just used the `slot` that was saved in the `fork_choice_store`. That seems like it would be a faithful representation of the slot when we saved it. I added the `genesis_time: u64` to the `BeaconChain`. It's small, constant and nice to have around. Since we're using FC for the fin/just checkpoints, we no longer get the `0x00..00` roots at genesis. You can see I had to remove a work-around in `ef-tests` here: b56be3bc2. I can't find any reason why this would be an issue, if anything I think it'll be better since the genesis-alias has caught us out a few times (0x00..00 isn't actually a real root). Edit: I did find a case where the `network` expected the 0x00..00 alias and patched it here: 3f26ac3e2. You'll notice a lot of changes in tests. Generally, tests should be functionally equivalent. Here are the things creating the most diff-noise in tests: - Changing tests to be `tokio::async` tests. - Adding `.await` to fork choice, block processing and block production functions. - Refactor of the `canonical_head` "API" provided by the `BeaconChain`. E.g., `chain.canonical_head.cached_head()` instead of `chain.canonical_head.read()`. - Wrapping `SignedBeaconBlock` in an `Arc`. - In the `beacon_chain/tests/block_verification`, we can't use the `lazy_static` `CHAIN_SEGMENT` variable anymore since it's generated with an async function. We just generate it in each test, not so efficient but hopefully insignificant. I had to disable `rayon` concurrent tests in the `fork_choice` tests. This is because the use of `rayon` and `block_on` was causing a panic. Co-authored-by: Mac L <mjladson@pm.me>
185 lines
5.2 KiB
Rust
185 lines
5.2 KiB
Rust
#![cfg(not(debug_assertions))] // Tests run too slow in debug.
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use beacon_chain::test_utils::BeaconChainHarness;
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use execution_layer::test_utils::{generate_pow_block, DEFAULT_TERMINAL_BLOCK};
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use types::*;
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const VALIDATOR_COUNT: usize = 32;
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type E = MainnetEthSpec;
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fn verify_execution_payload_chain<T: EthSpec>(chain: &[FullPayload<T>]) {
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let mut prev_ep: Option<FullPayload<T>> = None;
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for ep in chain {
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assert!(*ep != FullPayload::default());
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assert!(ep.block_hash() != ExecutionBlockHash::zero());
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// Check against previous `ExecutionPayload`.
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if let Some(prev_ep) = prev_ep {
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assert_eq!(prev_ep.block_hash(), ep.execution_payload.parent_hash);
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assert_eq!(
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prev_ep.execution_payload.block_number + 1,
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ep.execution_payload.block_number
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);
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}
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prev_ep = Some(ep.clone());
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}
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}
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#[tokio::test]
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// TODO(merge): This isn't working cause the non-zero values in `initialize_beacon_state_from_eth1`
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// are causing failed lookups to the execution node. I need to come back to this.
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#[should_panic]
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async fn merge_with_terminal_block_hash_override() {
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let altair_fork_epoch = Epoch::new(0);
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let bellatrix_fork_epoch = Epoch::new(0);
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let mut spec = E::default_spec();
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spec.altair_fork_epoch = Some(altair_fork_epoch);
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spec.bellatrix_fork_epoch = Some(bellatrix_fork_epoch);
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let genesis_pow_block_hash = generate_pow_block(
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spec.terminal_total_difficulty,
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DEFAULT_TERMINAL_BLOCK,
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0,
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ExecutionBlockHash::zero(),
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)
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.unwrap()
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.block_hash;
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spec.terminal_block_hash = genesis_pow_block_hash;
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let harness = BeaconChainHarness::builder(E::default())
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.spec(spec)
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.deterministic_keypairs(VALIDATOR_COUNT)
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.fresh_ephemeral_store()
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.mock_execution_layer()
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.build();
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assert_eq!(
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harness
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.execution_block_generator()
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.latest_block()
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.unwrap()
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.block_hash(),
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genesis_pow_block_hash,
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"pre-condition"
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);
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assert!(
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harness
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.chain
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.head_snapshot()
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.beacon_block
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.as_merge()
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.is_ok(),
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"genesis block should be a merge block"
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);
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let mut execution_payloads = vec![];
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for i in 0..E::slots_per_epoch() * 3 {
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harness.extend_slots(1).await;
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let block = &harness.chain.head_snapshot().beacon_block;
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let execution_payload = block.message().body().execution_payload().unwrap().clone();
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if i == 0 {
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assert_eq!(execution_payload.block_hash(), genesis_pow_block_hash);
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}
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execution_payloads.push(execution_payload);
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}
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verify_execution_payload_chain(execution_payloads.as_slice());
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}
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#[tokio::test]
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async fn base_altair_merge_with_terminal_block_after_fork() {
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let altair_fork_epoch = Epoch::new(4);
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let altair_fork_slot = altair_fork_epoch.start_slot(E::slots_per_epoch());
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let bellatrix_fork_epoch = Epoch::new(8);
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let merge_fork_slot = bellatrix_fork_epoch.start_slot(E::slots_per_epoch());
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let mut spec = E::default_spec();
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spec.altair_fork_epoch = Some(altair_fork_epoch);
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spec.bellatrix_fork_epoch = Some(bellatrix_fork_epoch);
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let mut execution_payloads = vec![];
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let harness = BeaconChainHarness::builder(E::default())
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.spec(spec)
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.deterministic_keypairs(VALIDATOR_COUNT)
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.fresh_ephemeral_store()
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.mock_execution_layer()
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.build();
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/*
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* Start with the base fork.
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*/
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assert!(harness.chain.head_snapshot().beacon_block.as_base().is_ok());
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/*
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* Do the Altair fork.
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*/
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harness.extend_to_slot(altair_fork_slot).await;
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let altair_head = &harness.chain.head_snapshot().beacon_block;
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assert!(altair_head.as_altair().is_ok());
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assert_eq!(altair_head.slot(), altair_fork_slot);
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/*
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* Do the merge fork, without a terminal PoW block.
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*/
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harness.extend_to_slot(merge_fork_slot).await;
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let merge_head = &harness.chain.head_snapshot().beacon_block;
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assert!(merge_head.as_merge().is_ok());
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assert_eq!(merge_head.slot(), merge_fork_slot);
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assert_eq!(
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*merge_head.message().body().execution_payload().unwrap(),
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FullPayload::default()
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);
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/*
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* Next merge block shouldn't include an exec payload.
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*/
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harness.extend_slots(1).await;
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let one_after_merge_head = &harness.chain.head_snapshot().beacon_block;
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assert_eq!(
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*one_after_merge_head
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.message()
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.body()
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.execution_payload()
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.unwrap(),
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FullPayload::default()
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);
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assert_eq!(one_after_merge_head.slot(), merge_fork_slot + 1);
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/*
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* Trigger the terminal PoW block.
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*/
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harness
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.execution_block_generator()
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.move_to_terminal_block()
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.unwrap();
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/*
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* Next merge block should include an exec payload.
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*/
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for _ in 0..4 {
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harness.extend_slots(1).await;
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let block = &harness.chain.head_snapshot().beacon_block;
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execution_payloads.push(block.message().body().execution_payload().unwrap().clone());
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}
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verify_execution_payload_chain(execution_payloads.as_slice());
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}
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