f22fcb3b2a
* canonicalize_replace_cache * canonicalize_replace_client Now it is clear at the call site that if there are duplicate copies of the data between the cache and the caller, which copy gets replaced. Additionally data parameter is now const-correct. If it is not going to be replaced (canonicalize_replace_cache), then the shared_ptr to the client data is const.
NodeStore
Introduction
A NodeObject is a simple object that the Ledger uses to store entries. It is
comprised of a type, a hash and a blob. It can be uniquely
identified by the hash, which is a 256 bit hash of the blob. The blob is a
variable length block of serialized data. The type identifies what the blob
contains. The fields are as follows:
mType
An enumeration that determines what the blob holds. There are four different types of objects stored.
-
ledger
A ledger header.
-
transaction
A signed transaction.
-
account node
A node in a ledger's account state tree.
-
transaction node
A node in a ledger's transaction tree.
-
mHash
A 256-bit hash of the blob.
mData
A blob containing the payload. Stored in the following format.
| Byte | ||
|---|---|---|
| 0...7 | unused | |
| 8 | type | NodeObjectType enumeration |
| 9...end | data | body of the object data |
The NodeStore provides an interface that stores, in a persistent database, a
collection of NodeObjects that rippled uses as its primary representation of
ledger entries. All ledger entries are stored as NodeObjects and as such, need
to be persisted between launches. If a NodeObject is accessed and is not in
memory, it will be retrieved from the database.
Backend
The NodeStore implementation provides the Backend abstract interface,
which lets different key/value databases to be chosen at run-time. This allows
experimentation with different engines. Improvements in the performance of the
NodeStore are a constant area of research. The database can be specified in
the configuration file [node_db] section as follows.
One or more lines of key / value pairs
Example:
type=RocksDB
path=rocksdb
compression=1
Choices for 'type' (not case-sensitive)
- HyperLevelDB
An improved version of LevelDB (preferred).
- LevelDB
Google's LevelDB database (deprecated).
- none
Use no backend.
- RocksDB
Facebook's RocksDB database, builds on LevelDB.
- SQLite
Use SQLite.
'path' speficies where the backend will store its data files.
Choices for 'compression'
-
0 off
-
1 on (default)