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bolt_provider.go
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bolt_provider.go
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package boltdb
import (
"encoding/binary"
"fmt"
"sync"
"github.com/boltdb/bolt"
"github.com/golang/protobuf/proto"
)
//BoltProvider persistence provider built on top of boltdb
type BoltProvider struct {
snapshotInterval int
mu sync.RWMutex
db *bolt.DB
}
//NewBoltProvider create new persistence provider with boltdb backend
func NewBoltProvider(snapshotInterval int, db *bolt.DB) *BoltProvider {
return &BoltProvider{
snapshotInterval: snapshotInterval,
db: db,
}
}
//Restart does who lnows what
func (provider *BoltProvider) Restart() {
//TODO: find out what it's for
}
//GetSnapshotInterval returns snapshot interval for provider
func (provider *BoltProvider) GetSnapshotInterval() int {
return provider.snapshotInterval
}
//GetSnapshot returns last snapshot and event index
func (provider *BoltProvider) GetSnapshot(actorName string) (snapshot interface{}, eventIndex int, ok bool) {
found := true
err := provider.db.View(func(tx *bolt.Tx) error {
//Get or create actor bucket
b := tx.Bucket([]byte(actorName))
if b == nil {
found = false
return nil
}
//Get snapshot event index; set found false if `se` does not exist
eb := b.Get([]byte("se"))
if eb == nil {
found = false
return nil
}
eventIndex = decodeInt(eb)
//Get snapshot; set found false if `sd` does not exist
sd := b.Get([]byte("sd"))
if sd == nil {
snapshot = nil
return nil
}
instance, err := cUnmarshal(sd)
if err != nil {
return err
}
snapshot = instance
return nil
})
if err != nil {
panic(fmt.Errorf("failed to read snapshot %d for %s: %v", eventIndex, actorName, err))
}
return snapshot, eventIndex, found
}
//PersistSnapshot saves snapshot and event index
func (provider *BoltProvider) PersistSnapshot(actorName string, eventIndex int, snapshot proto.Message) {
c, err := cMarshal(snapshot)
if err != nil {
panic(err)
}
err = provider.db.Update(func(tx *bolt.Tx) error {
b, err := tx.CreateBucketIfNotExists([]byte(actorName))
if err != nil {
return fmt.Errorf("failed to create bucket %s: %v", actorName, err)
}
err = b.Put([]byte("se"), encodeInt(eventIndex))
if err != nil {
return err
}
err = b.Put([]byte("sd"), c)
if err != nil {
return err
}
return nil
})
if err != nil {
panic(err)
}
}
//GetEvents execute callback for each event in store for actor after event index
func (provider *BoltProvider) GetEvents(actorName string, eventIndexStart int, callback func(e interface{})) {
events := []proto.Message{}
err := provider.db.View(func(tx *bolt.Tx) error {
//Get or create actor bucket
b := tx.Bucket([]byte(actorName))
if b == nil {
return nil
}
//Get events bucket
e := b.Bucket([]byte("events"))
if e == nil {
return nil
}
//get events after index
c := e.Cursor()
for k, v := c.Seek(encodeInt(eventIndexStart)); k != nil; k, v = c.Next() {
event, err := cUnmarshal(v)
if err != nil {
panic(err)
}
events = append(events, event)
}
return nil
})
if err != nil {
panic(fmt.Errorf("failed to read events for %s: %v", actorName, err))
}
for _, event := range events {
callback(event)
}
}
//PersistEvent save event into the store
func (provider *BoltProvider) PersistEvent(actorName string, eventIndex int, event proto.Message) {
c, err := cMarshal(event)
if err != nil {
panic(err)
}
err = provider.db.Update(func(tx *bolt.Tx) error {
b, err := tx.CreateBucketIfNotExists([]byte(actorName))
if err != nil {
return fmt.Errorf("failed to create bucket %s: %v", actorName, err)
}
e, err := b.CreateBucketIfNotExists([]byte("events"))
if err != nil {
return fmt.Errorf("failed to create events bucket %s: %v", actorName, err)
}
err = e.Put(encodeInt(eventIndex), c)
if err != nil {
return err
}
return nil
})
if err != nil {
panic(err)
}
}
func encodeInt(i int) []byte {
v := uint32(i)
buf := make([]byte, 4)
binary.BigEndian.PutUint32(buf, v)
return buf
}
func decodeInt(b []byte) int {
x := binary.BigEndian.Uint32(b)
return int(x)
}