storage

Documentation

Index

• Constants
• type Storage
  • func CreateRocksDBStorage(baseFile string, cacheSize uint) (Storage, error)

Constants

const (
	KeyVersion  = 1
	MetadataKey = 1
	EntryKey    = 10
	EntryValue  = 3
)

These have to match constants in leveldb_native.h

Types

type Storage

type Storage interface {
	// Methods for all kinds of metadata used for maintenance and operation
	GetUintMetadata(key string) (uint64, error)
	GetMetadata(key string) ([]byte, error)
	SetUintMetadata(key string, val uint64) error
	SetMetadata(key string, val []byte) error

	// Methods for the Raft index
	AppendEntry(e *common.Entry) error

	// Get term and data for entry. Return term 0 if not found.
	GetEntry(index uint64) (*common.Entry, error)

	// Get entries >= since, with a maximum count of "uint".
	// "filter" is a function that must return true for any valid entries.
	GetEntries(since uint64, max uint, filter func(*common.Entry) bool) ([]common.Entry, error)

	// Return the highest index and term in the database
	GetLastIndex() (uint64, uint64, error)

	// Return the lowest index in the databsae
	GetFirstIndex() (uint64, error)

	// Return index and term of everything from index to the end
	GetEntryTerms(index uint64) (map[uint64]uint64, error)

	// Delete everything that is greater than or equal to the index
	DeleteEntriesAfter(index uint64) error

	// Truncate removes all entries OLDER than "minIndex" and returns
	// the number removed. It may take some time, so should be run in a
	// goroutine. It is idempotent in case it is interrupted.
	// Return the number of entries actually deleted
	TruncateBefore(minIndex uint64) error

	// CalculateTruncate decides which entries should be truncated,
	// ensuring that at least "minEntries" are left
	// in the database, that any entries younger than "minAge" are retained,
	// and that any index including or after "minIndex" is retained.
	// It has to scan the database, so it may take some time.
	// It returns an index that can be used as input to "Truncate".
	CalculateTruncate(minEntries uint64, minAge time.Duration, minIndex uint64) (uint64, error)

	// Maintenance
	Close()
	Delete() error
	GetDataPath() string
	Dump(out io.Writer, max int)
}

Storage is an interface that abstracts all persistence-related operations in changeagent. It is the only interface that other modules should use within the project.

func CreateRocksDBStorage

func CreateRocksDBStorage(baseFile string, cacheSize uint) (Storage, error)

CreateRocksDBStorage creates an instance of the Storage interface using RocksDB.

The "baseFile" parameter refers to the name of a directory where RocksDB can store its data. RocksDB will create many files inside this directory. To create an empty database, make sure that it is empty.

The "cacheSize" parameter specifies the maximum number of bytes to use in memory for an LRU cache of database contents. How this cache is used is up to RocksDB.