This refactors and simplifies the code in blockchain to use the new more
efficient chain views.
An overview of the logic changes are as follows:
- Remove inMainChain from block nodes since that can now be efficiently
determined by using the chain view
- Track the best chain via a chain view instead of a single block node
- Use the tip of the best chain view everywhere bestNode was used
- Update chain view tip instead of updating best node
- Remove height map and associated lock in favor of chain view
- Use chain view NodeByHeight everywhere height map was used
- Change reorg logic to use more efficient chain view fork finding logic
- Change block locator code over to use more efficient chain view logic
- Remove now unused block-index-based block locator code
- Move BlockLocator definition to chain.go
- Move BlockLocatorFromHash and LatestBlockLocator to chain.go
- Update both to use more efficient chain view logic
- Rework several functions to use chain view for main chain detection
- fetchMainChainBlockByNode
- BlockByHeight
- MainChainHasBlock
- findPreviousCheckpoint
- IsCheckpointCandidate
This exposes the ability to more efficiently create a block locator from
a chain view for a given block node by using their ability to do O(1)
lookups.
It also adds tests to ensure the behavior is correct.
This implements a new type in the blockchain package that takes
advantage of the fact that all block nodes are now in memory to provide
a flat view of a specific chain of blocks (a specific branch of the
overall block tree) from a given tip all the way back to the genesis
block along with several convenience functions such as efficiently
comparing two views, quickly finding the fork point (if any) between two
views, and O(1) lookup of the node at a specific height.
The view is not currently used, but the intent is that the code will be
refactored to make use of these views to simplify and optimize several
areas such as best chain selection and reorg logic and finding successor
nodes. They will also greatly simplify the process of disconnecting the
download logic from the connection logic.
Since the ultimate intent is for there to be a long-lived chain view
instance for the current best chain, this also implements efficient
handling of setting the tip to new values including domain-specific
capacity increase handling which chooses the desired increase amount
more intelligently than the default algorithm, which would way
overshoot, as well as adds some additional space when the view is
initialized.
A comprehensive suite of tests is provided to ensure the chain views
behave correctly.
