## Issue Addressed
The non-finality period on Pyrmont between epochs [`9114`](https://pyrmont.beaconcha.in/epoch/9114) and [`9182`](https://pyrmont.beaconcha.in/epoch/9182) was contributed to by all the `lighthouse_team` validators going down. The nodes saw excessive CPU and RAM usage, resulting in the system to kill the `lighthouse bn` process. The `Restart=on-failure` directive for `systemd` caused the process to bounce in ~10-30m intervals.
Diagnosis with `heaptrack` showed that the `BeaconChain::produce_unaggregated_attestation` function was calling `store::beacon_state::get_full_state` and sometimes resulting in a tree hash cache allocation. These allocations were approximately the size of the hosts physical memory and still allocated when `lighthouse bn` was killed by the OS.
There was no CPU analysis (e.g., `perf`), but the `BeaconChain::produce_unaggregated_attestation` is very CPU-heavy so it is reasonable to assume it is the cause of the excessive CPU usage, too.
## Proposed Changes
`BeaconChain::produce_unaggregated_attestation` has two paths:
1. Fast path: attesting to the head slot or later.
2. Slow path: attesting to a slot earlier than the head block.
Path (2) is the only path that calls `store::beacon_state::get_full_state`, therefore it is the path causing this excessive CPU/RAM usage.
This PR removes the current functionality of path (2) and replaces it with a static error (`BeaconChainError::AttestingPriorToHead`).
This change reduces the generality of `BeaconChain::produce_unaggregated_attestation` (and therefore [`/eth/v1/validator/attestation_data`](https://ethereum.github.io/eth2.0-APIs/#/Validator/produceAttestationData)), but I argue that this functionality is an edge-case and arguably a violation of the [Honest Validator spec](https://github.com/ethereum/eth2.0-specs/blob/dev/specs/phase0/validator.md).
It's possible that a validator goes back to a prior slot to "catch up" and submit some missed attestations. This change would prevent such behaviour, returning an error. My concerns with this catch-up behaviour is that it is:
- Not specified as "honest validator" attesting behaviour.
- Is behaviour that is risky for slashing (although, all validator clients *should* have slashing protection and will eventually fail if they do not).
- It disguises clock-sync issues between a BN and VC.
## Additional Info
It's likely feasible to implement path (2) if we implement some sort of caching mechanism. This would be a multi-week task and this PR gets the issue patched in the short term. I haven't created an issue to add path (2), instead I think we should implement it if we get user-demand.
## Issue Addressed
Closes#1557
## Proposed Changes
Modify the pruning algorithm so that it mutates the head-tracker _before_ committing the database transaction to disk, and _only if_ all the heads to be removed are still present in the head-tracker (i.e. no concurrent mutations).
In the process of writing and testing this I also had to make a few other changes:
* Use internal mutability for all `BeaconChainHarness` functions (namely the RNG and the graffiti), in order to enable parallel calls (see testing section below).
* Disable logging in harness tests unless the `test_logger` feature is turned on
And chose to make some clean-ups:
* Delete the `NullMigrator`
* Remove type-based configuration for the migrator in favour of runtime config (simpler, less duplicated code)
* Use the non-blocking migrator unless the blocking migrator is required. In the store tests we need the blocking migrator because some tests make asserts about the state of the DB after the migration has run.
* Rename `validators_keypairs` -> `validator_keypairs` in the `BeaconChainHarness`
## Testing
To confirm that the fix worked, I wrote a test using [Hiatus](https://crates.io/crates/hiatus), which can be found here:
https://github.com/michaelsproul/lighthouse/tree/hiatus-issue-1557
That test can't be merged because it inserts random breakpoints everywhere, but if you check out that branch you can run the test with:
```
$ cd beacon_node/beacon_chain
$ cargo test --release --test parallel_tests --features test_logger
```
It should pass, and the log output should show:
```
WARN Pruning deferred because of a concurrent mutation, message: this is expected only very rarely!
```
## Additional Info
This is a backwards-compatible change with no impact on consensus.
The PR:
* Adds the ability to generate a crucial test scenario that isn't possible with `BeaconChainHarness` (i.e. two blocks occupying the same slot; previously forks necessitated skipping slots):
* New testing API: Instead of repeatedly calling add_block(), you generate a sorted `Vec<Slot>` and leave it up to the framework to generate blocks at those slots.
* Jumping backwards to an earlier epoch is a hard error, so that tests necessarily generate blocks in a epoch-by-epoch manner.
* Configures the test logger so that output is printed on the console in case a test fails. The logger also plays well with `--nocapture`, contrary to the existing testing framework
* Rewrites existing fork pruning tests to use the new API
* Adds a tests that triggers finalization at a non epoch boundary slot
* Renamed `BeaconChainYoke` to `BeaconChainTestingRig` because the former has been too confusing
* Fixed multiple tests (e.g. `block_production_different_shuffling_long`, `delete_blocks_and_states`, `shuffling_compatible_simple_fork`) that relied on a weird (and accidental) feature of the old `BeaconChainHarness` that attestations aren't produced for epochs earlier than the current one, thus masking potential bugs in test cases.
Co-authored-by: Michael Sproul <michael@sigmaprime.io>
## Issue Addressed
NA
## Proposed Changes
- Refactor the `bls` crate to support multiple BLS "backends" (e.g., milagro, blst, etc).
- Removes some duplicate, unused code in `common/rest_types/src/validator.rs`.
- Removes the old "upgrade legacy keypairs" functionality (these were unencrypted keys that haven't been supported for a few testnets, no one should be using them anymore).
## Additional Info
Most of the files changed are just inconsequential changes to function names.
## TODO
- [x] Optimization levels
- [x] Infinity point: https://github.com/supranational/blst/issues/11
- [x] Ensure milagro *and* blst are tested via CI
- [x] What to do with unsafe code?
- [x] Test infinity point in signature sets
* Layer do_atomically() abstractions properly
* Reduce allocs and DRY get_key_for_col()
* Parameterize HotColdDB with hot and cold item stores
* -impl Store for MemoryStore
* Replace Store uses with HotColdDB
* Ditch Store trait
* cargo fmt
* Style fix
* Readd missing dep that broke the build
* Add PH & MS slot clock changes
* Account for genesis time
* Add progress on duties refactor
* Add simple is_aggregator bool to val subscription
* Start work on attestation_verification.rs
* Add progress on ObservedAttestations
* Progress with ObservedAttestations
* Fix tests
* Add observed attestations to the beacon chain
* Add attestation observation to processing code
* Add progress on attestation verification
* Add first draft of ObservedAttesters
* Add more tests
* Add observed attesters to beacon chain
* Add observers to attestation processing
* Add more attestation verification
* Create ObservedAggregators map
* Remove commented-out code
* Add observed aggregators into chain
* Add progress
* Finish adding features to attestation verification
* Ensure beacon chain compiles
* Link attn verification into chain
* Integrate new attn verification in chain
* Remove old attestation processing code
* Start trying to fix beacon_chain tests
* Split adding into pools into two functions
* Add aggregation to harness
* Get test harness working again
* Adjust the number of aggregators for test harness
* Fix edge-case in harness
* Integrate new attn processing in network
* Fix compile bug in validator_client
* Update validator API endpoints
* Fix aggreagation in test harness
* Fix enum thing
* Fix attestation observation bug:
* Patch failing API tests
* Start adding comments to attestation verification
* Remove unused attestation field
* Unify "is block known" logic
* Update comments
* Supress fork choice errors for network processing
* Add todos
* Tidy
* Add gossip attn tests
* Disallow test harness to produce old attns
* Comment out in-progress tests
* Partially address pruning tests
* Fix failing store test
* Add aggregate tests
* Add comments about which spec conditions we check
* Dont re-aggregate
* Split apart test harness attn production
* Fix compile error in network
* Make progress on commented-out test
* Fix skipping attestation test
* Add fork choice verification tests
* Tidy attn tests, remove dead code
* Remove some accidentally added code
* Fix clippy lint
* Rename test file
* Add block tests, add cheap block proposer check
* Rename block testing file
* Add observed_block_producers
* Tidy
* Switch around block signature verification
* Finish block testing
* Remove gossip from signature tests
* First pass of self review
* Fix deviation in spec
* Update test spec tags
* Start moving over to hashset
* Finish moving observed attesters to hashmap
* Move aggregation pool over to hashmap
* Make fc attn borrow again
* Fix rest_api compile error
* Fix missing comments
* Fix monster test
* Uncomment increasing slots test
* Address remaining comments
* Remove unsafe, use cfg test
* Remove cfg test flag
* Fix dodgy comment
* Ignore aggregates that are already known.
* Unify aggregator modulo logic
* Fix typo in logs
* Refactor validator subscription logic
* Avoid reproducing selection proof
* Skip HTTP call if no subscriptions
* Rename DutyAndState -> DutyAndProof
* Tidy logs
* Print root as dbg
* Fix compile errors in tests
* Fix compile error in test
* Start adding interop genesis state to lcli
* Use more efficient method to generate genesis state
* Remove duplicate int_to_bytes32
* Add lcli command to change state genesis time
* Add option to allow VC to start with unsynced BN
* Set VC to do parallel key loading
* Don't default to dummy eth1 backend
* Add endpoint to dump operation pool
* Add metrics for op pool
* Remove state clone for slot notifier
* Add mem size approximation for tree hash cache
* Avoid cloning tree hash when getting head
* Avoid cloning tree hash when getting head
* Add working arena-based cached tree hash
* Add another benchmark
* Add pre-allocation for caches
* Make cache nullable
* Fix bugs in cache tree hash
* Add validator tree hash optimization
* Optimize hash_concat
* Make hash32_concat return fixed-len array
* Fix failing API tests
* Add new beacon state cache struct
* Add validator-specific cache
* Separate list and values arenas
* Add parallel validator registry hashing
* Remove MultiTreeHashCache
* Remove cached tree hash macro
* Fix failing tree hash test
* Address Michael's comments
* Add CachedTreeHash impl for ef tests
* Fix messy merge conflict
* Optimize attestation production
* Add first basic optimizations
* Fix SlotOutOfBounds error
* Resolved missed merge conflicts
* Fix another missed merge conflict
* Fix more merge conflict issues
* Add `StateSkipConfig`
* Fix test compile errors
* Add failing test
* Fix bug, make tests pass
* Add comment
* Delete unused function
* Replace deleted comment
