83 lines
3.2 KiB
Nim
83 lines
3.2 KiB
Nim
# beacon_chain
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# Copyright (c) 2023 Status Research & Development GmbH
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# Licensed and distributed under either of
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# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
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# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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import
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std/uri,
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stew/io2, chronos, chronos/apps/http/httpclient, snappy,
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../spec/[digest, forks], ../spec/datatypes/base
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import network_metadata
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export network_metadata
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type
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HttpFetchError* = object of CatchableError
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status*: int
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DigestMismatchError* = object of CatchableError
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proc downloadFile(url: Uri): Future[seq[byte]] {.async.} =
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var httpSession = HttpSessionRef.new()
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let response = await httpSession.fetch(url)
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if response[0] == 200:
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return response[1]
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else:
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raise (ref HttpFetchError)(
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msg: "Unexpected status code " & $response[0] & " when fetching " & $url,
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status: response[0])
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proc fetchGenesisBytes*(
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metadata: Eth2NetworkMetadata,
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genesisStateUrlOverride = none(Uri)): Future[seq[byte]] {.async.} =
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case metadata.genesis.kind
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of NoGenesis:
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raiseAssert "fetchGenesisBytes should be called only when metadata.hasGenesis is true"
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of BakedIn:
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result = @(metadata.genesis.bakedBytes)
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of BakedInUrl:
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result = await downloadFile(genesisStateUrlOverride.get(parseUri metadata.genesis.url))
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# Under the built-in default URL, we serve a snappy-encoded BeaconState in order
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# to reduce the size of the downloaded file with roughly 50% (this precise ratio
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# depends on the number of validator recors). The user is still free to provide
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# any URL which may serve an uncompressed state (e.g. a Beacon API endpoint)
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#
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# Since a SSZ-encoded BeaconState will start with a LittleEndian genesis time
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# (64 bits) while a snappy framed stream will always start with a fixed header
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# that will decoded as a timestamp with the value 5791996851603375871 (year 2153).
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#
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# TODO: A more complete solution will implement compression on the HTTP level,
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# by relying on the Content-Encoding header to determine the compression
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# algorithm. The detection method used here will not interfere with such
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# an implementation and it may remain useful when dealing with misconfigured
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# HTTP servers.
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if result.isSnappyFramedStream:
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result = decodeFramed(result)
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let state = newClone(readSszForkedHashedBeaconState(metadata.cfg, result))
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withState(state[]):
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if forkyState.root != metadata.genesis.digest:
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raise (ref DigestMismatchError)(
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msg: "The downloaded genesis state cannot be verified (checksum mismatch)")
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of UserSuppliedFile:
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result = readAllBytes(metadata.genesis.path).tryGet()
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proc sourceDesc*(metadata: GenesisMetadata): string =
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case metadata.kind
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of NoGenesis:
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"no genesis"
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of BakedIn:
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metadata.networkName
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of BakedInUrl:
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metadata.url
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of UserSuppliedFile:
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metadata.path
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when isMainModule:
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let holeskyMetadata = getMetadataForNetwork("holesky")
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io2.writeFile(
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"holesky-genesis.ssz",
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waitFor holeskyMetadata.fetchGenesisBytes()
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).expect("success")
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