Paul Hauner a764c3b247 Handle early blocks (#2155) ... ## Issue Addressed NA ## Problem this PR addresses There's an issue where Lighthouse is banning a lot of peers due to the following sequence of events: 1. Gossip block 0xabc arrives ~200ms early - It is propagated across the network, with respect to [`MAXIMUM_GOSSIP_CLOCK_DISPARITY`](https://github.com/ethereum/eth2.0-specs/blob/v1.0.0/specs/phase0/p2p-interface.md#why-is-there-maximum_gossip_clock_disparity-when-validating-slot-ranges-of-messages-in-gossip-subnets). - However, it is not imported to our database since the block is early. 2. Attestations for 0xabc arrive, but the block was not imported. - The peer that sent the attestation is down-voted. - Each unknown-block attestation causes a score loss of 1, the peer is banned at -100. - When the peer is on an attestation subnet there can be hundreds of attestations, so the peer is banned quickly (before the missed block can be obtained via rpc). ## Potential solutions I can think of three solutions to this: 1. Wait for attestation-queuing (#635) to arrive and solve this. - Easy - Not immediate fix. - Whilst this would work, I don't think it's a perfect solution for this particular issue, rather (3) is better. 1. Allow importing blocks with a tolerance of `MAXIMUM_GOSSIP_CLOCK_DISPARITY`. - Easy - ~~I have implemented this, for now.~~ 1. If a block is verified for gossip propagation (i.e., signature verified) and it's within `MAXIMUM_GOSSIP_CLOCK_DISPARITY`, then queue it to be processed at the start of the appropriate slot. - More difficult - Feels like the best solution, I will try to implement this. **This PR takes approach (3).** ## Changes included - Implement the `block_delay_queue`, based upon a [`DelayQueue`](https://docs.rs/tokio-util/0.6.3/tokio_util/time/delay_queue/struct.DelayQueue.html) which can store blocks until it's time to import them. - Add a new `DelayedImportBlock` variant to the `beacon_processor::WorkEvent` enum to handle this new event. - In the `BeaconProcessor`, refactor a `tokio::select!` to a struct with an explicit `Stream` implementation. I experienced some issues with `tokio::select!` in the block delay queue and I also found it hard to debug. I think this explicit implementation is nicer and functionally equivalent (apart from the fact that `tokio::select!` randomly chooses futures to poll, whereas now we're deterministic). - Add a testing framework to the `beacon_processor` module that tests this new block delay logic. I also tested a handful of other operations in the beacon processor (attns, slashings, exits) since it was super easy to copy-pasta the code from the `http_api` tester. - To implement these tests I added the concept of an optional `work_journal_tx` to the `BeaconProcessor` which will spit out a log of events. I used this in the tests to ensure that things were happening as I expect. - The tests are a little racey, but it's hard to avoid that when testing timing-based code. If we see CI failures I can revise. I haven't observed *any* failures due to races on my machine or on CI yet. - To assist with testing I allowed for directly setting the time on the `ManualSlotClock`. - I gave the `beacon_processor::Worker` a `Toolbox` for two reasons; (a) it avoids changing tons of function sigs when you want to pass a new object to the worker and (b) it seemed cute.		2021-02-24 03:08:52 +00:00
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src	Handle early blocks (#2155)	2021-02-24 03:08:52 +00:00
Cargo.toml	Handle early blocks (#2155)	2021-02-24 03:08:52 +00:00