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Use async code when interacting with EL (#3244)

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## 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
2022-07-03 05:36:50 +00:00
parent e5212f1320
commit be4e261e74
106 changed files with 6515 additions and 4538 deletions
Download Patch File Download Diff File Expand all files Collapse all files

33
testing/state_transition_vectors/src/exit.rs
View File

@@ -37,11 +37,12 @@ impl Default for ExitTest {
}
impl ExitTest {
fn block_and_pre_state(self) -> (SignedBeaconBlock<E>, BeaconState<E>) {
async fn block_and_pre_state(self) -> (SignedBeaconBlock<E>, BeaconState<E>) {
let harness = get_harness::<E>(
self.state_epoch.start_slot(E::slots_per_epoch()),
VALIDATOR_COUNT,
);
)
.await;
let mut state = harness.get_current_state();
(self.state_modifier)(&mut state);
@@ -49,11 +50,12 @@ impl ExitTest {
let validator_index = self.validator_index;
let exit_epoch = self.exit_epoch;
let (signed_block, state) =
harness.make_block_with_modifier(state.clone(), state.slot() + 1, |block| {
let (signed_block, state) = harness
.make_block_with_modifier(state.clone(), state.slot() + 1, |block| {
harness.add_voluntary_exit(block, validator_index, exit_epoch);
block_modifier(&harness, block);
});
})
.await;
(signed_block, state)
}
@@ -72,12 +74,12 @@ impl ExitTest {
}
#[cfg(all(test, not(debug_assertions)))]
fn run(self) -> BeaconState<E> {
async fn run(self) -> BeaconState<E> {
let spec = &E::default_spec();
let expected = self.expected.clone();
assert_eq!(STATE_EPOCH, spec.shard_committee_period);
let (block, mut state) = self.block_and_pre_state();
let (block, mut state) = self.block_and_pre_state().await;
let result = Self::process(&block, &mut state);
@@ -86,8 +88,8 @@ impl ExitTest {
state
}
fn test_vector(self, title: String) -> TestVector {
let (block, pre_state) = self.block_and_pre_state();
async fn test_vector(self, title: String) -> TestVector {
let (block, pre_state) = self.block_and_pre_state().await;
let mut post_state = pre_state.clone();
let (post_state, error) = match Self::process(&block, &mut post_state) {
Ok(_) => (Some(post_state), None),
@@ -334,14 +336,14 @@ mod custom_tests {
);
}
#[test]
fn valid() {
let state = ExitTest::default().run();
#[tokio::test]
async fn valid() {
let state = ExitTest::default().run().await;
assert_exited(&state, VALIDATOR_INDEX as usize);
}
#[test]
fn valid_three() {
#[tokio::test]
async fn valid_three() {
let state = ExitTest {
block_modifier: Box::new(|harness, block| {
harness.add_voluntary_exit(block, 1, STATE_EPOCH);
@@ -349,7 +351,8 @@ mod custom_tests {
}),
..ExitTest::default()
}
.run();
.run()
.await;
for i in &[VALIDATOR_INDEX, 1, 2] {
assert_exited(&state, *i as usize);

10
testing/state_transition_vectors/src/macros.rs
View File

@@ -4,11 +4,11 @@
/// - `mod tests`: runs all the test vectors locally.
macro_rules! vectors_and_tests {
($($name: ident, $test: expr),*) => {
pub fn vectors() -> Vec<TestVector> {
pub async fn vectors() -> Vec<TestVector> {
let mut vec = vec![];
$(
vec.push($test.test_vector(stringify!($name).into()));
vec.push($test.test_vector(stringify!($name).into()).await);
)*
vec
@@ -18,9 +18,9 @@ macro_rules! vectors_and_tests {
mod tests {
use super::*;
$(
#[test]
fn $name() {
$test.run();
#[tokio::test]
async fn $name() {
$test.run().await;
}
)*
}

31
testing/state_transition_vectors/src/main.rs
View File

@@ -25,8 +25,9 @@ pub const BASE_VECTOR_DIR: &str = "vectors";
pub const SLOT_OFFSET: u64 = 1;
/// Writes all known test vectors to `CARGO_MANIFEST_DIR/vectors`.
fn main() {
match write_all_vectors() {
#[tokio::main]
async fn main() {
match write_all_vectors().await {
Ok(()) => exit(0),
Err(e) => {
eprintln!("Error: {}", e);
@@ -49,7 +50,7 @@ lazy_static! {
static ref KEYPAIRS: Vec<Keypair> = generate_deterministic_keypairs(VALIDATOR_COUNT);
}
fn get_harness<E: EthSpec>(
async fn get_harness<E: EthSpec>(
slot: Slot,
validator_count: usize,
) -> BeaconChainHarness<EphemeralHarnessType<E>> {
@@ -61,23 +62,25 @@ fn get_harness<E: EthSpec>(
let skip_to_slot = slot - SLOT_OFFSET;
if skip_to_slot > Slot::new(0) {
let state = harness.get_current_state();
harness.add_attested_blocks_at_slots(
state,
Hash256::zero(),
(skip_to_slot.as_u64()..slot.as_u64())
.map(Slot::new)
.collect::<Vec<_>>()
.as_slice(),
(0..validator_count).collect::<Vec<_>>().as_slice(),
);
harness
.add_attested_blocks_at_slots(
state,
Hash256::zero(),
(skip_to_slot.as_u64()..slot.as_u64())
.map(Slot::new)
.collect::<Vec<_>>()
.as_slice(),
(0..validator_count).collect::<Vec<_>>().as_slice(),
)
.await;
}
harness
}
/// Writes all vectors to file.
fn write_all_vectors() -> Result<(), String> {
write_vectors_to_file("exit", &exit::vectors())
async fn write_all_vectors() -> Result<(), String> {
write_vectors_to_file("exit", &exit::vectors().await)
}
/// Writes a list of `vectors` to the `title` dir.