Engine API: add getPayloadBodies method #146
Conversation
Good question. I don't know how convenient JSON-RPC batching interface is across different client libraries. I think that as it's straightforward for EL clients to implement this proposal (and it is because of already existing logic) we can accept batching to be enshrined. |
Valuable input on that from Discord https://discord.com/channels/595666850260713488/692062809701482577/931309418879012945:
Batching enshrined in a method semantics is preferable. |
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Is there any concern about JSON ser/deser overhead? If I'm following correctly it's sending what was previously p2p traffic over json. I'd guess that the overhead will be significant and may become the bottleneck for sync. |
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So I think the ser/deser overhead is pretty minimal. |
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When EL clients are snap syncing and CL clients are up to head optimistically. Will the EL clients respond to requests of getPayloadBodies? |
Good question. Does CL client have to serve blocks to remote peers while syncing? |
If it is optimistically syncing yes, it can gossip blocks regularly. Typically we would have those blocks on a hot cache. But we may be requested old blocks. |
## Proposed Changes
Reduce post-merge disk usage by not storing finalized execution payloads in Lighthouse's database.
:warning: **This is achieved in a backwards-incompatible way for networks that have already merged** :warning:. Kiln users and shadow fork enjoyers will be unable to downgrade after running the code from this PR. The upgrade migration may take several minutes to run, and can't be aborted after it begins.
The main changes are:
- New column in the database called `ExecPayload`, keyed by beacon block root.
- The `BeaconBlock` column now stores blinded blocks only.
- Lots of places that previously used full blocks now use blinded blocks, e.g. analytics APIs, block replay in the DB, etc.
- On finalization:
- `prune_abanonded_forks` deletes non-canonical payloads whilst deleting non-canonical blocks.
- `migrate_db` deletes finalized canonical payloads whilst deleting finalized states.
- Conversions between blinded and full blocks are implemented in a compositional way, duplicating some work from Sean's PR #3134.
- The execution layer has a new `get_payload_by_block_hash` method that reconstructs a payload using the EE's `eth_getBlockByHash` call.
- I've tested manually that it works on Kiln, using Geth and Nethermind.
- This isn't necessarily the most efficient method, and new engine APIs are being discussed to improve this: ethereum/execution-apis#146.
- We're depending on the `ethers` master branch, due to lots of recent changes. We're also using a workaround for gakonst/ethers-rs#1134.
- Payload reconstruction is used in the HTTP API via `BeaconChain::get_block`, which is now `async`. Due to the `async` fn, the `blocking_json` wrapper has been removed.
- Payload reconstruction is used in network RPC to serve blocks-by-{root,range} responses. Here the `async` adjustment is messier, although I think I've managed to come up with a reasonable compromise: the handlers take the `SendOnDrop` by value so that they can drop it on _task completion_ (after the `fn` returns). Still, this is introducing disk reads onto core executor threads, which may have a negative performance impact (thoughts appreciated).
## Additional Info
- [x] For performance it would be great to remove the cloning of full blocks when converting them to blinded blocks to write to disk. I'm going to experiment with a `put_block` API that takes the block by value, breaks it into a blinded block and a payload, stores the blinded block, and then re-assembles the full block for the caller.
- [x] We should measure the latency of blocks-by-root and blocks-by-range responses.
- [x] We should add integration tests that stress the payload reconstruction (basic tests done, issue for more extensive tests: #3159)
- [x] We should (manually) test the schema v9 migration from several prior versions, particularly as blocks have changed on disk and some migrations rely on being able to load blocks.
Co-authored-by: Paul Hauner <[email protected]>
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We're seeing issues with ELs timing out under a flood of |
Agree. We have some users that reporting this problem. |
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Closing in favour of #218 |
Proposal
engine_getPayloadBodiesmethod to the Engine APIblock_hashvalues the method returnsExecutionPayloadBodyobjects which consist oftransactionslist of the corresponding payloadsGetBlockBodiesmessage in ETH protocol -- this is the crux of this proposalConcerns
The main concern is that retrieval of the bodies by hashes doesn't allow for utilizing linearity of block data as if the request was made by block numbers. Utilizing the linearity property opens up an opportunity for more optimal way of accessing this information, especially it makes sense for the finalized part of the blockchain.
See #137 and discussion thread for more details
Implementations