Validator historical state restoration #922
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,126 @@ | ||
| import pkg/ethers/provider | ||
| import pkg/chronos | ||
| import pkg/questionable | ||
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| import ../logutils | ||
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| from ../clock import SecondsSince1970 | ||
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| logScope: | ||
| topics = "marketplace onchain provider" | ||
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| proc raiseProviderError(message: string) {.raises: [ProviderError].} = | ||
| raise newException(ProviderError, message) | ||
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| proc blockNumberAndTimestamp*(provider: Provider, blockTag: BlockTag): | ||
| Future[(UInt256, UInt256)] {.async: (raises: [ProviderError]).} = | ||
| without latestBlock =? await provider.getBlock(blockTag): | ||
| raiseProviderError("Could not get latest block") | ||
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| without latestBlockNumber =? latestBlock.number: | ||
| raiseProviderError("Could not get latest block number") | ||
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| return (latestBlockNumber, latestBlock.timestamp) | ||
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| proc binarySearchFindClosestBlock( | ||
| provider: Provider, | ||
| epochTime: int, | ||
| low: UInt256, | ||
| high: UInt256): Future[UInt256] {.async: (raises: [ProviderError]).} = | ||
| let (_, lowTimestamp) = | ||
| await provider.blockNumberAndTimestamp(BlockTag.init(low)) | ||
| let (_, highTimestamp) = | ||
| await provider.blockNumberAndTimestamp(BlockTag.init(high)) | ||
| if abs(lowTimestamp.truncate(int) - epochTime) < | ||
| abs(highTimestamp.truncate(int) - epochTime): | ||
| return low | ||
| else: | ||
| return high | ||
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| proc binarySearchBlockNumberForEpoch( | ||
| provider: Provider, | ||
| epochTime: UInt256, | ||
| latestBlockNumber: UInt256, | ||
| earliestBlockNumber: UInt256): Future[UInt256] | ||
| {.async: (raises: [ProviderError]).} = | ||
| var low = earliestBlockNumber | ||
| var high = latestBlockNumber | ||
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| while low <= high: | ||
| if low == 0 and high == 0: | ||
| return low | ||
| let mid = (low + high) div 2 | ||
| let (midBlockNumber, midBlockTimestamp) = | ||
| await provider.blockNumberAndTimestamp(BlockTag.init(mid)) | ||
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| if midBlockTimestamp < epochTime: | ||
| low = mid + 1 | ||
| elif midBlockTimestamp > epochTime: | ||
| high = mid - 1 | ||
| else: | ||
| return midBlockNumber | ||
| # NOTICE that by how the binary search is implemented, when it finishes | ||
| # low is always greater than high - this is why we use high, where | ||
| # intuitively we would use low: | ||
| await provider.binarySearchFindClosestBlock( | ||
| epochTime.truncate(int), low=high, high=low) | ||
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| proc blockNumberForEpoch*( | ||
| provider: Provider, | ||
| epochTime: SecondsSince1970): Future[UInt256] | ||
| {.async: (raises: [ProviderError]).} = | ||
| let epochTimeUInt256 = epochTime.u256 | ||
| let (latestBlockNumber, latestBlockTimestamp) = | ||
| await provider.blockNumberAndTimestamp(BlockTag.latest) | ||
| let (earliestBlockNumber, earliestBlockTimestamp) = | ||
| await provider.blockNumberAndTimestamp(BlockTag.earliest) | ||
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| # Initially we used the average block time to predict | ||
| # the number of blocks we need to look back in order to find | ||
| # the block number corresponding to the given epoch time. | ||
| # This estimation can be highly inaccurate if block time | ||
| # was changing in the past or is fluctuating and therefore | ||
| # we used that information initially only to find out | ||
| # if the available history is long enough to perform effective search. | ||
| # It turns out we do not have to do that. There is an easier way. | ||
| # | ||
| # First we check if the given epoch time equals the timestamp of either | ||
| # the earliest or the latest block. If it does, we just return the | ||
| # block number of that block. | ||
| # | ||
| # Otherwise, if the earliest available block is not the genesis block, | ||
| # we should check the timestamp of that earliest block and if it is greater | ||
| # than the epoch time, we should issue a warning and return | ||
| # that earliest block number. | ||
| # In all other cases, thus when the earliest block is not the genesis | ||
| # block but its timestamp is not greater than the requested epoch time, or | ||
| # if the earliest available block is the genesis block, | ||
| # (which means we have the whole history available), we should proceed with | ||
| # the binary search. | ||
| # | ||
| # Additional benefit of this method is that we do not have to rely | ||
| # on the average block time, which not only makes the whole thing | ||
| # more reliable, but also easier to test. | ||
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| # Are lucky today? | ||
| if earliestBlockTimestamp == epochTimeUInt256: | ||
| return earliestBlockNumber | ||
| if latestBlockTimestamp == epochTimeUInt256: | ||
| return latestBlockNumber | ||
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| if earliestBlockNumber > 0 and earliestBlockTimestamp > epochTimeUInt256: | ||
| let availableHistoryInDays = | ||
| (latestBlockTimestamp - earliestBlockTimestamp) div | ||
| 1.days.secs.u256 | ||
| warn "Short block history detected.", earliestBlockTimestamp = | ||
| earliestBlockTimestamp, days = availableHistoryInDays | ||
| return earliestBlockNumber | ||
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| return await provider.binarySearchBlockNumberForEpoch( | ||
| epochTimeUInt256, latestBlockNumber, earliestBlockNumber) | ||
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| proc pastBlockTag*(provider: Provider, | ||
| blocksAgo: int): | ||
| Future[BlockTag] {.async: (raises: [ProviderError]).} = | ||
| let head = await provider.getBlockNumber() | ||
| return BlockTag.init(head - blocksAgo.abs.u256) | ||
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Might be beneficial to preserve the original exception otherwise the underlying reason for the failure will be lost:
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Used like:
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Also, callers can pull out the parent exception msg using
msdDetaillike this:There was a problem hiding this comment.
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We cannot use:
because (as you yourself pointed out earlier)
getBlockreturns anOptionand not aResult. Right?So if there was an original
ProviderErrorcaused bygetBlockit will naturally bubble-up so, we do not have to do anything about it I suppose. But thengetBlock, which is defined as this:can still return
Nonebecauseeth_getBlockByNumberis defined like this:This is why I am raising
ProviderErrorwhen this happen, but we have no data about underlying exception that causedeth_getBlockByNumberto returnNone.So I think in this case everything can stays as it is, right?
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Good point, sorry I missed that
getBlockreturns anOption👍I don't think it's an error really, just that the ethereum client can return null if the block doesn't exist.
What you have looks good 👍