This introduces a new indexing infrastructure for supporting optional
indexes using the new database and blockchain infrastructure along with
two concrete indexer implementations which provide both a
transaction-by-hash and a transaction-by-address index.
The new infrastructure is mostly separated into a package named indexers
which is housed under the blockchain package. In order to support this,
a new interface named IndexManager has been introduced in the blockchain
package which provides methods to be notified when the chain has been
initialized and when blocks are connected and disconnected from the main
chain. A concrete implementation of an index manager is provided by the
new indexers package.
The new indexers package also provides a new interface named Indexer
which allows the index manager to manage concrete index implementations
which conform to the interface.
The following is high level overview of the main index infrastructure
changes:
- Define a new IndexManager interface in the blockchain package and
modify the package to make use of the interface when specified
- Create a new indexers package
- Provides an Index interface which allows concrete indexes to plugin
to an index manager
- Provides a concrete IndexManager implementation
- Handles the lifecycle of all indexes it manages
- Tracks the index tips
- Handles catching up disabled indexes that have been reenabled
- Handles reorgs while the index was disabled
- Invokes the appropriate methods for all managed indexes to allow
them to index and deindex the blocks and transactions
- Implement a transaction-by-hash index
- Makes use of internal block IDs to save a significant amount of
space and indexing costs over the old transaction index format
- Implement a transaction-by-address index
- Makes use of a leveling scheme in order to provide a good tradeoff
between space required and indexing costs
- Supports enabling and disabling indexes at will
- Support the ability to drop indexes if they are no longer desired
The following is an overview of the btcd changes:
- Add a new index logging subsystem
- Add new options --txindex and --addrindex in order to enable the
optional indexes
- NOTE: The transaction index will automatically be enabled when the
address index is enabled because it depends on it
- Add new options --droptxindex and --dropaddrindex to allow the indexes
to be removed
- NOTE: The address index will also be removed when the transaction
index is dropped because it depends on it
- Update getrawtransactions RPC to make use of the transaction index
- Reimplement the searchrawtransaction RPC that makes use of the address
index
- Update sample-btcd.conf to include sample usage for the new optional
index flags
This removes the intermediate transaction log that was introduced as a
part of the database cache as a workaround for leveldb batches causing
massive memory usage spikes in favor of the recently introduced leveldb
transaction interface which no longer has the memory usage issues.
This approach is preferred because it can avoid the extra memory needed
for the transaction log and therefore all of the intermediate states as
well. As a result, the default cache size has been doubled since it
equals roughly the same amount of overall memory usage and the flush
interval has been raised as well.
This commit adds a database cache layer to the ffldb database backend so
that callers can commit multiple transactions without having to incur
the overhead of a disk sync on every new block.
This commit contains a complete redesign and rewrite of the database
package that approaches things in a vastly different manner than the
previous version. This is the first part of several stages that will be
needed to ultimately make use of this new package.
Some of the reason for this were discussed in #255, however a quick
summary is as follows:
- The previous database could only contain blocks on the main chain and
reorgs required deleting the blocks from the database. This made it
impossible to store orphans and could make external RPC calls for
information about blocks during the middle of a reorg fail.
- The previous database interface forced a high level of bitcoin-specific
intelligence such as spend tracking into each backend driver.
- The aforementioned point led to making it difficult to implement new
backend drivers due to the need to repeat a lot of non-trivial logic
which is better handled at a higher layer, such as the blockchain
package.
- The old database stored all blocks in leveldb. This made it extremely
inefficient to do things such as lookup headers and individual
transactions since the entire block had to be loaded from leveldb (which
entails it doing data copies) to get access.
In order to address all of these concerns, and others not mentioned, the
database interface has been redesigned as follows:
- Two main categories of functionality are provided: block storage and
metadata storage
- All block storage and metadata storage are done via read-only and
read-write MVCC transactions with both manual and managed modes
- Support for multiple concurrent readers and a single writer
- Readers use a snapshot and therefore are not blocked by the writer
- Some key properties of the block storage and retrieval API:
- It is generic and does NOT contain additional bitcoin logic such spend
tracking and block linking
- Provides access to the raw serialized bytes so deserialization is not
forced for callers that don't need it
- Support for fetching headers via independent functions which allows
implementations to provide significant optimizations
- Ability to efficiently retrieve arbitrary regions of blocks
(transactions, scripts, etc)
- A rich metadata storage API is provided:
- Key/value with arbitrary data
- Support for buckets and nested buckets
- Bucket iteration through a couple of different mechanisms
- Cursors for efficient and direct key seeking
- Supports registration of backend database implementations
- Comprehensive test coverage
- Provides strong documentation with example usage
This commit also contains an implementation of the previously discussed
interface named ffldb (flat file plus leveldb metadata backend). Here
is a quick overview:
- Highly optimized for read performance with consistent write performance
regardless of database size
- All blocks are stored in flat files on the file system
- Bulk block region fetching is optimized to perform linear reads which
improves performance on spindle disks
- Anti-corruption mechanisms:
- Flat files contain full block checksums to quickly an easily detect
database corruption without needing to do expensive merkle root
calculations
- Metadata checksums
- Open reconciliation
- Extensive test coverage:
- Comprehensive blackbox interface testing
- Whitebox testing which uses intimate knowledge to exercise uncommon
failure paths such as deleting files out from under the database
- Corruption tests (replacing random data in the files)
In addition, this commit also contains a new tool under the new database
directory named dbtool which provides a few basic commands for testing the
database. It is designed around commands, so it could be useful to expand
on in the future.
Finally, this commit addresses the following issues:
- Adds support for and therefore closes#255
- Fixes#199
- Fixes#201
- Implements and closes#256
- Obsoletes and closes#257
- Closes#247 once the required chain and btcd modifications are in place
to make use of this new code
