rippled/src/ripple/nodestore

NodeStore

Introduction

A NodeObject is a simple object that the Ledger uses to store entries. It is comprised of a type, a hash, a ledger index 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.

• mLedgerIndex

An unsigned integer that uniquely identifies the ledger in which this NodeObject appears.

• mData

A blob containing the payload. Stored in the following format.

Byte
0...3	ledger index	32-bit big endian integer
4...7	reserved ledger index	32-bit big endian integer
8	type	NodeObjectType enumeration
9...end	data	body of the object data

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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)