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2 Commits
Author | SHA1 | Message | Date | |
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Dave Collins
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a59ac5b18f
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multi: Rework utxoset/view to use outpoints.
This modifies the utxoset in the database and related UtxoViewpoint to store and work with unspent transaction outputs on a per-output basis instead of at a transaction level. This was inspired by similar recent changes in Bitcoin Core. The primary motivation is to simplify the code, pave the way for a utxo cache, and generally focus on optimizing runtime performance. The tradeoff is that this approach does somewhat increase the size of the serialized utxoset since it means that the transaction hash is duplicated for each output as a part of the key and some additional details such as whether the containing transaction is a coinbase and the block height it was a part of are duplicated in each output. However, in practice, the size difference isn't all that large, disk space is relatively cheap, certainly cheaper than memory, and it is much more important to provide more efficient runtime operation since that is the ultimate purpose of the daemon. While performing this conversion, it also simplifies the code to remove the transaction version information from the utxoset as well as the spend journal. The logic for only serializing it under certain circumstances is complicated and it isn't actually used anywhere aside from the gettxout RPC where it also isn't used by anything important either. Consequently, this also removes the version field of the gettxout RPC result. The utxos in the database are automatically migrated to the new format with this commit and it is possible to interrupt and resume the migration process. Finally, it also updates the tests for the new format and adds a new function to the tests to convert the old test data to the new format for convenience. The data has already been converted and updated in the commit. An overview of the changes are as follows: - Remove transaction version from both spent and unspent output entries - Update utxo serialization format to exclude the version - Modify the spend journal serialization format - The old version field is now reserved and always stores zero and ignores it when reading - This allows old entries to be used by new code without having to migrate the entire spend journal - Remove version field from gettxout RPC result - Convert UtxoEntry to represent a specific utxo instead of a transaction with all remaining utxos - Optimize for memory usage with an eye towards a utxo cache - Combine details such as whether the txout was contained in a coinbase, is spent, and is modified into a single packed field of bit flags - Align entry fields to eliminate extra padding since ultimately there will be a lot of these in memory - Introduce a free list for serializing an outpoint to the database key format to significantly reduce pressure on the GC - Update all related functions that previously dealt with transaction hashes to accept outpoints instead - Update all callers accordingly - Only add individually requested outputs from the mempool when constructing a mempool view - Modify the spend journal to always store the block height and coinbase information with every spent txout - Introduce code to handle fetching the missing information from another utxo from the same transaction in the event an old style entry is encountered - Make use of a database cursor with seek to do this much more efficiently than testing every possible output - Always decompress data loaded from the database now that a utxo entry only consists of a specific output - Introduce upgrade code to migrate the utxo set to the new format - Store versions of the utxoset and spend journal buckets - Allow migration process to be interrupted and resumed - Update all tests to expect the correct encodings, remove tests that no longer apply, and add new ones for the new expected behavior - Convert old tests for the legacy utxo format deserialization code to test the new function that is used during upgrade - Update the utxostore test data and add function that was used to convert it - Introduce a few new functions on UtxoViewpoint - AddTxOut for adding an individual txout versus all of them - addTxOut to handle the common code between the new AddTxOut and existing AddTxOuts - RemoveEntry for removing an individual txout - fetchEntryByHash for fetching any remaining utxo for a given transaction hash |
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Dave Collins
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491acd4ca6 |
blockchain: Rework to use new db interface.
This commit is the first stage of several that are planned to convert the blockchain package into a concurrent safe package that will ultimately allow support for multi-peer download and concurrent chain processing. The goal is to update btcd proper after each step so it can take advantage of the enhancements as they are developed. In addition to the aforementioned benefit, this staged approach has been chosen since it is absolutely critical to maintain consensus. Separating the changes into several stages makes it easier for reviewers to logically follow what is happening and therefore helps prevent consensus bugs. Naturally there are significant automated tests to help prevent consensus issues as well. The main focus of this stage is to convert the blockchain package to use the new database interface and implement the chain-related functionality which it no longer handles. It also aims to improve efficiency in various areas by making use of the new database and chain capabilities. The following is an overview of the chain changes: - Update to use the new database interface - Add chain-related functionality that the old database used to handle - Main chain structure and state - Transaction spend tracking - Implement a new pruned unspent transaction output (utxo) set - Provides efficient direct access to the unspent transaction outputs - Uses a domain specific compression algorithm that understands the standard transaction scripts in order to significantly compress them - Removes reliance on the transaction index and paves the way toward eventually enabling block pruning - Modify the New function to accept a Config struct instead of inidividual parameters - Replace the old TxStore type with a new UtxoViewpoint type that makes use of the new pruned utxo set - Convert code to treat the new UtxoViewpoint as a rolling view that is used between connects and disconnects to improve efficiency - Make best chain state always set when the chain instance is created - Remove now unnecessary logic for dealing with unset best state - Make all exported functions concurrent safe - Currently using a single chain state lock as it provides a straight forward and easy to review path forward however this can be improved with more fine grained locking - Optimize various cases where full blocks were being loaded when only the header is needed to help reduce the I/O load - Add the ability for callers to get a snapshot of the current best chain stats in a concurrent safe fashion - Does not block callers while new blocks are being processed - Make error messages that reference transaction outputs consistently use <transaction hash>:<output index> - Introduce a new AssertError type an convert internal consistency checks to use it - Update tests and examples to reflect the changes - Add a full suite of tests to ensure correct functionality of the new code The following is an overview of the btcd changes: - Update to use the new database and chain interfaces - Temporarily remove all code related to the transaction index - Temporarily remove all code related to the address index - Convert all code that uses transaction stores to use the new utxo view - Rework several calls that required the block manager for safe concurrency to use the chain package directly now that it is concurrent safe - Change all calls to obtain the best hash to use the new best state snapshot capability from the chain package - Remove workaround for limits on fetching height ranges since the new database interface no longer imposes them - Correct the gettxout RPC handler to return the best chain hash as opposed the hash the txout was found in - Optimize various RPC handlers: - Change several of the RPC handlers to use the new chain snapshot capability to avoid needlessly loading data - Update several handlers to use new functionality to avoid accessing the block manager so they are able to return the data without blocking when the server is busy processing blocks - Update non-verbose getblock to avoid deserialization and serialization overhead - Update getblockheader to request the block height directly from chain and only load the header - Update getdifficulty to use the new cached data from chain - Update getmininginfo to use the new cached data from chain - Update non-verbose getrawtransaction to avoid deserialization and serialization overhead - Update gettxout to use the new utxo store versus loading full transactions using the transaction index The following is an overview of the utility changes: - Update addblock to use the new database and chain interfaces - Update findcheckpoint to use the new database and chain interfaces - Remove the dropafter utility which is no longer supported NOTE: The transaction index and address index will be reimplemented in another commit. |