MossDB is a in-memory, persistent and embedded key-value store.
Features:
- Key-value memory store, just use a simple map to store key/value
- Transactions supported
- AOL persistent, use the wal to store every commit, just like redis append-only file
- TTL supported, user can set the key with expire time that based on time heap
- Watch interface, caller will receive event when the value of key changes
- Embedded with a simple API
- Multi storage engine, now it support Map and RadixTree as backend storage
The architecture of MossDB as follows:
To start using MossDB, just use go get:
go get github.com/qingwave/mossdb
There is a simple example shows how to use MossDB.
package main
import (
"context"
"errors"
"log"
"time"
"github.com/qingwave/mossdb"
)
func () {
// create db instance
db, err := mossdb.New(&mossdb.Config{})
if err != nil {
log.Fatal(err)
}
// set, get, delete data
db.Set("key1", []byte("val1"))
log.Printf("get key1: %s", db.Get("key1"))
db.Delete("key1", []byte("val1"))
}The database allows for rich transactions, in which multiple objects are inserted, updated or deleted. Note that one transaction allowed at a time.
db.Tx(func(tx *mossdb.Tx) error {
val1 := tx.Get("key1")
tx.Set("key2", val1)
return nil
})Watch interface just like etcd Watch(watch a key or prefix key), caller will receive event when the watched keys modified.
func Watch(db *mossdb.DB) {
key := "watch-key"
go func() {
db.Set(key, mossdb.Val("val1"))
db.Set(key, mossdb.Val("val2"))
db.Delete(key)
time.Sleep(100 * time.Second)
db.Set(key, mossdb.Val("val3"))
}()
ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
defer cancel()
ch := db.Watch(ctx, key)
for {
select {
case <-ctx.Done():
log.Printf("context done")
return
case resp, ok := <-ch:
if !ok {
log.Printf("watch done")
return
}
log.Printf("receive event: %s, key: %s, new val: %s", resp.Event.Op, resp.Event.Key, resp.Event.Val)
}
}
}Key with expired time in useful sometimes, MossDB use a time heap to expire key near real-time.
db.Set("key-ttl", []byte("val-ttl"), mossdb.WithTTL(100*time.Millisecond))