README
¶
kanta
A embeddable database for Go written in pure Go. It is based on LSM-trees meaning that it is more fit for high writes and low reads. The database contains fault-tolerance in the form of logs for in-memory tables and some other things.
Simple usage
You firstly need to install it:
go get -u github.com/nireo/kantadb
Then the basic usage is:
package main
import (
"log"
"github.com/nireo/kantadb"
)
func main() {
db := kantadb.New(kantadb.DefaultConfiguration())
defer db.Stop()
db.Run()
// put a value
db.Put("hello", "world")
// get the value
value, ok := db.Get("hello")
if !ok {
log.Println("value has not been found")
}
log.Printf("got value %s", value)
// delete the value
db.Delete("hello")
}
How it works
Firstly there is a simple in-memory table, which has a certain max capacity. Once that capacity gets filled, the in-memory table is placed in to a queue, in which it will be written to disk. The queue is checked every 25-100 milliseconds and then if that queue is not empty, tables from the queue are written to disk as sstables.
The combination of in-memory table log files and the sstables makes persistence possible. All the log files and sstables are checked when the database is started up again. Log files are used to make sure in-memory data doesn't get lost if the database suddenly shuts down.
Todo
- Add transactions
- Stop using mutexes and start using channels for concurrency
- Add levels
- Improve the compaction process
Documentation
¶
Index ¶
- Constants
- type Config
- type DB
- func (db *DB) CompactNTables(n int) error
- func (db *DB) Delete(key string) error
- func (db *DB) Get(key string) (string, bool)
- func (db *DB) GetCompactableFiles() []string
- func (db *DB) GetDirectory() string
- func (db *DB) GetSSTableIndex(filename string) int
- func (db *DB) GetTableSize() int
- func (db *DB) MergeFiles(f1, f2 string) error
- func (db *DB) Put(key, val string) error
- func (db *DB) Run() error
- func (db *DB) Stop() error
- type WRequest
Constants ¶
const MaxMemSize int64 = 1024 * 256
256 kb
const MaxSSTableSize int64 = 1024 * 1014 * 24
24 mb
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Config ¶
Config represents different parameters to change te default behaviour of the database
func DefaultConfiguration ¶
func DefaultConfiguration() *Config
DefaultConfiguration returns a database config that has some default values
type DB ¶
type DB struct {
Alive bool
MEM *mem.MEM
SSTables []*sstable.SSTable
MEMQueue []*mem.MEM
// contains filtered or unexported fields
}
DB represents the database as a whole.
func (*DB) CompactNTables ¶
compactNTables combines the last n sstables.
func (*DB) Delete ¶
Delete has almost exactly the same functionality as read, but instead we set the value of the key to a TombstoneValue which just corresponds to a string where the first character is a null-byte. We cannot remove the key from the in-memory table since it might reside in the queue or sstable. The key will be ultimately deleted when sstable compaction happens.
func (*DB) Get ¶
Get tries to find the wanted key from the in-memory table, and if not found checks it then checks the queue for the value. If the value is not found in the queue, check the sstables. If the value corresponds to a TombstoneValue return a invalid key since the key was "deleted".
func (*DB) GetCompactableFiles ¶
GetCompactableFiles returns all of the files in the SSTable directory that are small enough.
func (*DB) GetDirectory ¶
GetDirectory returns the directory in which all of the files are stored.
func (*DB) GetSSTableIndex ¶
GetSSTableIndex returns the index of the sstable with a given filename
func (*DB) GetTableSize ¶
GetTableSize returns the amount of sstables indexed
func (*DB) MergeFiles ¶
func (*DB) Put ¶
Put writes a value into the in-memory table and also checks if the amount of items in the in-memory table exceeds the amount specified in the database configuation. If the number is exceeded, add the in-memory table to the start of the queue.
Source Files
Directories