lighthouse-pulse/consensus
Michael Sproul 703c33bdc7 Fix head tracker concurrency bugs (#1771)
## 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.
2020-10-19 05:58:39 +00:00
..
cached_tree_hash Update external deps (#1711) 2020-10-05 08:22:19 +00:00
fork_choice Fix head tracker concurrency bugs (#1771) 2020-10-19 05:58:39 +00:00
int_to_bytes Update external deps (#1711) 2020-10-05 08:22:19 +00:00
merkle_proof Implement matches! macro (#1777) 2020-10-15 21:42:43 +00:00
proto_array Update external deps (#1711) 2020-10-05 08:22:19 +00:00
safe_arith Remove saturating arith from state_processing (#1644) 2020-09-25 05:18:21 +00:00
serde_utils Update external deps (#1711) 2020-10-05 08:22:19 +00:00
ssz Update external deps (#1711) 2020-10-05 08:22:19 +00:00
ssz_derive Update external deps (#1711) 2020-10-05 08:22:19 +00:00
ssz_types Update external deps (#1711) 2020-10-05 08:22:19 +00:00
state_processing Update external deps (#1711) 2020-10-05 08:22:19 +00:00
swap_or_not_shuffle Update external deps (#1711) 2020-10-05 08:22:19 +00:00
tree_hash Update external deps (#1711) 2020-10-05 08:22:19 +00:00
tree_hash_derive Update external deps (#1711) 2020-10-05 08:22:19 +00:00
types Fix epoch, slot, and effective balance quoting (#1756) 2020-10-11 23:58:12 +00:00