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https://github.com/sigp/lighthouse.git
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Use async code when interacting with EL (#3244)
## 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>
This commit is contained in:
Paul Hauner
@@ -56,7 +56,7 @@ fn get_harness(validator_count: usize) -> BeaconChainHarness<EphemeralHarnessTyp
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fn get_valid_unaggregated_attestation<T: BeaconChainTypes>(
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chain: &BeaconChain<T>,
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) -> (Attestation<T::EthSpec>, usize, usize, SecretKey, SubnetId) {
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let head = chain.head().expect("should get head");
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let head = chain.head_snapshot();
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let current_slot = chain.slot().expect("should get slot");
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let mut valid_attestation = chain
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@@ -106,7 +106,8 @@ fn get_valid_aggregated_attestation<T: BeaconChainTypes>(
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chain: &BeaconChain<T>,
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aggregate: Attestation<T::EthSpec>,
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) -> (SignedAggregateAndProof<T::EthSpec>, usize, SecretKey) {
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let state = &chain.head().expect("should get head").beacon_state;
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let head = chain.head_snapshot();
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let state = &head.beacon_state;
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let current_slot = chain.slot().expect("should get slot");
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let committee = state
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@@ -155,7 +156,8 @@ fn get_non_aggregator<T: BeaconChainTypes>(
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chain: &BeaconChain<T>,
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aggregate: &Attestation<T::EthSpec>,
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) -> (usize, SecretKey) {
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let state = &chain.head().expect("should get head").beacon_state;
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let head = chain.head_snapshot();
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let state = &head.beacon_state;
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let current_slot = chain.slot().expect("should get slot");
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let committee = state
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@@ -213,15 +215,17 @@ struct GossipTester {
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}
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impl GossipTester {
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pub fn new() -> Self {
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pub async fn new() -> Self {
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let harness = get_harness(VALIDATOR_COUNT);
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// Extend the chain out a few epochs so we have some chain depth to play with.
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harness.extend_chain(
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MainnetEthSpec::slots_per_epoch() as usize * 3 - 1,
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BlockStrategy::OnCanonicalHead,
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AttestationStrategy::AllValidators,
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);
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harness
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.extend_chain(
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MainnetEthSpec::slots_per_epoch() as usize * 3 - 1,
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BlockStrategy::OnCanonicalHead,
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AttestationStrategy::AllValidators,
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)
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.await;
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// Advance into a slot where there have not been blocks or attestations produced.
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harness.advance_slot();
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@@ -395,9 +399,10 @@ impl GossipTester {
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}
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}
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/// Tests verification of `SignedAggregateAndProof` from the gossip network.
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#[test]
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fn aggregated_gossip_verification() {
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#[tokio::test]
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async fn aggregated_gossip_verification() {
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GossipTester::new()
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.await
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/*
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* The following two tests ensure:
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*
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@@ -511,8 +516,7 @@ fn aggregated_gossip_verification() {
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let committee_len = tester
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.harness
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.chain
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.head()
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.unwrap()
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.head_snapshot()
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.beacon_state
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.get_beacon_committee(tester.slot(), a.message.aggregate.data.index)
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.expect("should get committees")
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@@ -612,7 +616,7 @@ fn aggregated_gossip_verification() {
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tester.valid_aggregate.message.aggregate.clone(),
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None,
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&sk,
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&chain.head_info().unwrap().fork,
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&chain.canonical_head.cached_head().head_fork(),
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chain.genesis_validators_root,
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&chain.spec,
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)
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@@ -669,9 +673,10 @@ fn aggregated_gossip_verification() {
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}
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/// Tests the verification conditions for an unaggregated attestation on the gossip network.
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#[test]
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fn unaggregated_gossip_verification() {
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#[tokio::test]
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async fn unaggregated_gossip_verification() {
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GossipTester::new()
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.await
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/*
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* The following test ensures:
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*
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@@ -684,8 +689,7 @@ fn unaggregated_gossip_verification() {
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a.data.index = tester
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.harness
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.chain
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.head()
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.unwrap()
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.head_snapshot()
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.beacon_state
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.get_committee_count_at_slot(a.data.slot)
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.unwrap()
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@@ -924,16 +928,18 @@ fn unaggregated_gossip_verification() {
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/// Ensures that an attestation that skips epochs can still be processed.
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///
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/// This also checks that we can do a state lookup if we don't get a hit from the shuffling cache.
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#[test]
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fn attestation_that_skips_epochs() {
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#[tokio::test]
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async fn attestation_that_skips_epochs() {
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let harness = get_harness(VALIDATOR_COUNT);
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// Extend the chain out a few epochs so we have some chain depth to play with.
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harness.extend_chain(
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MainnetEthSpec::slots_per_epoch() as usize * 3 + 1,
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BlockStrategy::OnCanonicalHead,
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AttestationStrategy::SomeValidators(vec![]),
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);
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harness
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.extend_chain(
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MainnetEthSpec::slots_per_epoch() as usize * 3 + 1,
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BlockStrategy::OnCanonicalHead,
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AttestationStrategy::SomeValidators(vec![]),
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)
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.await;
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let current_slot = harness.chain.slot().expect("should get slot");
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let current_epoch = harness.chain.epoch().expect("should get epoch");
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@@ -992,16 +998,18 @@ fn attestation_that_skips_epochs() {
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.expect("should gossip verify attestation that skips slots");
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}
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#[test]
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fn attestation_to_finalized_block() {
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#[tokio::test]
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async fn attestation_to_finalized_block() {
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let harness = get_harness(VALIDATOR_COUNT);
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// Extend the chain out a few epochs so we have some chain depth to play with.
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harness.extend_chain(
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MainnetEthSpec::slots_per_epoch() as usize * 4 + 1,
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BlockStrategy::OnCanonicalHead,
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AttestationStrategy::AllValidators,
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);
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harness
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.extend_chain(
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MainnetEthSpec::slots_per_epoch() as usize * 4 + 1,
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BlockStrategy::OnCanonicalHead,
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AttestationStrategy::AllValidators,
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)
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.await;
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let finalized_checkpoint = harness
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.chain
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@@ -1067,16 +1075,18 @@ fn attestation_to_finalized_block() {
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.contains(earlier_block_root));
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}
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#[test]
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fn verify_aggregate_for_gossip_doppelganger_detection() {
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#[tokio::test]
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async fn verify_aggregate_for_gossip_doppelganger_detection() {
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let harness = get_harness(VALIDATOR_COUNT);
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// Extend the chain out a few epochs so we have some chain depth to play with.
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harness.extend_chain(
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MainnetEthSpec::slots_per_epoch() as usize * 3 - 1,
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BlockStrategy::OnCanonicalHead,
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AttestationStrategy::AllValidators,
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);
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harness
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.extend_chain(
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MainnetEthSpec::slots_per_epoch() as usize * 3 - 1,
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BlockStrategy::OnCanonicalHead,
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AttestationStrategy::AllValidators,
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)
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.await;
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// Advance into a slot where there have not been blocks or attestations produced.
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harness.advance_slot();
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@@ -1124,16 +1134,18 @@ fn verify_aggregate_for_gossip_doppelganger_detection() {
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.expect("should check if gossip aggregator was observed"));
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}
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#[test]
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fn verify_attestation_for_gossip_doppelganger_detection() {
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#[tokio::test]
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async fn verify_attestation_for_gossip_doppelganger_detection() {
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let harness = get_harness(VALIDATOR_COUNT);
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// Extend the chain out a few epochs so we have some chain depth to play with.
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harness.extend_chain(
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MainnetEthSpec::slots_per_epoch() as usize * 3 - 1,
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BlockStrategy::OnCanonicalHead,
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AttestationStrategy::AllValidators,
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);
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harness
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.extend_chain(
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MainnetEthSpec::slots_per_epoch() as usize * 3 - 1,
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BlockStrategy::OnCanonicalHead,
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AttestationStrategy::AllValidators,
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)
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.await;
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// Advance into a slot where there have not been blocks or attestations produced.
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harness.advance_slot();
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