fc91d2ccbf
This reworks the block index code such that it loads all of the headers
in the main chain at startup and constructs the full block index
accordingly.
Since the full index from the current best tip all the way back to the
genesis block is now guaranteed to be in memory, this also removes all
code related to dynamically loading the nodes and updates some of the
logic to take advantage of the fact traversing the block index can no
longer potentially fail. There are also many more optimizations and
simplifications that can be made in the future as a result of this.
Due to removing all of the extra overhead of tracking the dynamic state,
and ensuring the block node structs are aligned to eliminate extra
padding, the end result of a fully populated block index now takes quite
a bit less memory than the previous dynamically loaded version.
It also speeds up the initial startup process by roughly 2x since it is
faster to bulk load the nodes in order as opposed to dynamically loading
only the nodes near the tip in backwards order.
For example, here is some startup timing information before and after
this commit on a node that contains roughly 238,000 blocks:
7200 RPM HDD:
-------------
Startup time before this commit: ~7.71s
Startup time after this commit: ~3.47s
SSD:
----
Startup time before this commit: ~6.34s
Startup time after this commit: ~3.51s
Some additional benefits are:
- Since every block node is in memory, the code which reconstructs
headers from block nodes means that all headers can always be served
from memory which will be important since the network will be moving
to header-based semantics
- Several of the error paths can be removed since they are no longer
necessary
- It is no longer expensive to calculate CSV sequence locks or median
times of blocks way in the past
- It is much less expensive to calculate the initial states for the
various intervals such as the stake and voter version
- It will be possible to create much more efficient iteration and
simplified views of the overall index
An overview of the logic changes are as follows:
- Move AncestorNode from blockIndex to blockNode and greatly simplify
since it no longer has to deal with the possibility of dynamically
loading nodes and related failures
- Replace nodeAtHeightFromTopNode from BlockChain with RelativeAncestor
on blockNode and define it in terms of AncestorNode
- Move CalcPastMedianTime from blockIndex to blockNode and remove no
longer necessary test for nil
- Remove findNode and replace all of its uses with direct queries of the
block index
- Remove blockExists and replace all of its uses with direct queries of
the block index
- Remove all functions and fields related to dynamically loading nodes
- children and parentHash fields from blockNode
- depNodes from blockIndex
- loadBlockNode from blockIndex
- PrevNodeFromBlock from blockIndex
- {p,P}revNodeFromNode from blockIndex
- RemoveNode
- Replace all instances of iterating backwards through nodes to directly
access the parent now that nodes don't potentially need to be
dynamically loaded
- Introduce a lookupNode function on blockIndex which allows the
initialization code to locklessly query the index
- No longer take the chain lock when only access to the block index,
which has its own lock, is needed
- Removed the error paths from several functions that can no longer fail
- getReorganizeNodes
- findPrevTestNetDifficulty
- sumPurchasedTickets
- findStakeVersionPriorNode
- Removed all error paths related to node iteration that can no longer
fail
- Modify FetchUtxoView to return an empty view for the genesis block
|
||
|---|---|---|
| .. | ||
| chaingen | ||
| fullblocktests | ||
| indexers | ||
| internal | ||
| stake | ||
| testdata | ||
| accept.go | ||
| agendas_test.go | ||
| bench_test.go | ||
| blockindex_test.go | ||
| blockindex.go | ||
| blocklocator.go | ||
| chain_test.go | ||
| chain.go | ||
| chainio_test.go | ||
| chainio.go | ||
| chainquery.go | ||
| checkpoints.go | ||
| common_test.go | ||
| compress_test.go | ||
| compress.go | ||
| difficulty_test.go | ||
| difficulty.go | ||
| doc.go | ||
| error_test.go | ||
| error.go | ||
| example_test.go | ||
| fullblocks_test.go | ||
| fullblocksstakeversion_test.go | ||
| go.mod | ||
| go.modverify | ||
| log.go | ||
| mediantime_test.go | ||
| mediantime.go | ||
| merkle_test.go | ||
| merkle.go | ||
| notifications.go | ||
| process.go | ||
| prune.go | ||
| README.md | ||
| scriptval.go | ||
| sequencelock_test.go | ||
| sequencelock.go | ||
| stakeext.go | ||
| stakenode.go | ||
| stakeversion_test.go | ||
| stakeversion.go | ||
| subsidy_test.go | ||
| subsidy.go | ||
| thresholdstate_test.go | ||
| thresholdstate.go | ||
| timesorter_test.go | ||
| timesorter.go | ||
| upgrade.go | ||
| utxoviewpoint.go | ||
| validate_test.go | ||
| validate.go | ||
| votebits_test.go | ||
| votebits.go | ||
blockchain
Package blockchain implements Decred block handling and chain selection rules.
The test coverage is currently only around 60%, but will be increasing over
time. See test_coverage.txt for the gocov coverage report. Alternatively, if
you are running a POSIX OS, you can run the cov_report.sh script for a
real-time report. Package blockchain is licensed under the liberal ISC license.
There is an associated blog post about the release of this package here.
This package has intentionally been designed so it can be used as a standalone package for any projects needing to handle processing of blocks into the decred block chain.
Installation and Updating
$ go get -u github.com/decred/dcrd/blockchain
Decred Chain Processing Overview
Before a block is allowed into the block chain, it must go through an intensive series of validation rules. The following list serves as a general outline of those rules to provide some intuition into what is going on under the hood, but is by no means exhaustive:
- Reject duplicate blocks
- Perform a series of sanity checks on the block and its transactions such as verifying proof of work, timestamps, number and character of transactions, transaction amounts, script complexity, and merkle root calculations
- Compare the block against predetermined checkpoints for expected timestamps and difficulty based on elapsed time since the checkpoint
- Save the most recent orphan blocks for a limited time in case their parent blocks become available
- Stop processing if the block is an orphan as the rest of the processing depends on the block's position within the block chain
- Perform a series of more thorough checks that depend on the block's position within the block chain such as verifying block difficulties adhere to difficulty retarget rules, timestamps are after the median of the last several blocks, all transactions are finalized, checkpoint blocks match, and block versions are in line with the previous blocks
- Determine how the block fits into the chain and perform different actions accordingly in order to ensure any side chains which have higher difficulty than the main chain become the new main chain
- When a block is being connected to the main chain (either through reorganization of a side chain to the main chain or just extending the main chain), perform further checks on the block's transactions such as verifying transaction duplicates, script complexity for the combination of connected scripts, coinbase maturity, double spends, and connected transaction values
- Run the transaction scripts to verify the spender is allowed to spend the coins
- Insert the block into the block database
Examples
-
ProcessBlock Example
Demonstrates how to create a new chain instance and use ProcessBlock to attempt to add a block to the chain. This example intentionally attempts to insert a duplicate genesis block to illustrate how an invalid block is handled. -
CompactToBig Example
Demonstrates how to convert the compact "bits" in a block header which represent the target difficulty to a big integer and display it using the typical hex notation. -
BigToCompact Example
Demonstrates how to convert how to convert a target difficulty into the compact "bits" in a block header which represent that target difficulty.
License
Package blockchain is licensed under the copyfree ISC License.