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badger.go
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badger.go
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package badger
import (
"encoding/json"
"fmt"
"io"
"time"
"github.com/mishudark/eventhus"
"log"
"github.com/dgraph-io/badger"
)
//AggregateDB defines the collection to store the aggregate with their events
type AggregateDB struct {
ID string `json:"_id"`
Version int `json:"version"`
Events []EventDB `json:"events"`
}
//EventDB defines the structure of the events to be stored
type EventDB struct {
Type string `json:"event_type"`
AggregateID string `json:"_id"`
RawData []byte `json:"data,omitempty"`
data interface{}
Timestamp time.Time `json:"timestamp"`
AggregateType string `json:"aggregate_type"`
Version int `json:"version"`
}
//Client for access to boltdb
type Client struct {
session *badger.DB
}
//NewClient generates a new client for access to BadgerDB
func NewClient(dbDir string) (eventhus.EventStore, error) {
// Open the Badger database located in the /tmp/badger directory.
// It will be created if it doesn't exist.
opts := badger.DefaultOptions
opts.Dir = dbDir
opts.ValueDir = dbDir
session, err := badger.Open(opts)
if err != nil {
log.Fatal(err)
return nil, err
}
cli := &Client{
session,
}
return cli, nil
}
// CloseClient closes the db connection
func (c *Client) CloseClient() error {
return c.session.Close()
}
func (c *Client) save(events []eventhus.Event, version int, safe bool) error {
if len(events) == 0 {
return nil
}
// Build all event records, with incrementing versions starting from the
// original aggregate version.
eventsDB := make([]EventDB, len(events))
aggregateID := events[0].AggregateID
for i, event := range events {
// Create the event record with timestamp.
eventsDB[i] = EventDB{
Type: event.Type,
AggregateID: event.AggregateID,
Timestamp: time.Now(),
AggregateType: event.AggregateType,
Version: 1 + version + i,
}
// Marshal event data if there is any.
if event.Data != nil {
rawData, err := json.MarshalIndent(event.Data, "", "\t")
if err != nil {
return err
}
eventsDB[i].RawData = rawData
}
}
// Either insert a new aggregate or append to an existing.
if version == 0 {
aggregate := AggregateDB{
ID: aggregateID,
Version: len(eventsDB),
Events: eventsDB,
}
err := c.session.Update(func(txn *badger.Txn) error {
aggregateJSON, _ := json.MarshalIndent(aggregate, "", "\t")
err := txn.Set([]byte(aggregateID), aggregateJSON)
return err
})
return err
}
// Increment aggregate version on insert of new event record, and
// only insert if version of aggregate is matching (ie not changed
// since loading the aggregate).
err := c.session.Update(func(txn *badger.Txn) error {
item, err := txn.Get([]byte("aggregateID"))
if err != nil {
return err
}
val, err := item.Value()
if err != nil {
return err
}
var aggregateDB AggregateDB
for {
err := json.Unmarshal(val, &aggregateDB)
if err == io.EOF {
break
}
if err != nil {
return err
}
}
if safe && aggregateDB.Version != version {
return fmt.Errorf("There was an concurrent update of %s", aggregateID)
}
aggregateJSON, _ := json.MarshalIndent(aggregateDB, "", "\t")
aggregateDB.Version = len(eventsDB)
err2 := txn.Set([]byte(aggregateID), aggregateJSON)
if err2 != nil {
return err2
}
return nil
})
return err
}
//SafeSave store the events without check the current version
func (c *Client) SafeSave(events []eventhus.Event, version int) error {
return c.save(events, version, true)
}
//Save the events ensuring the current version
func (c *Client) Save(events []eventhus.Event, version int) error {
return c.save(events, version, false)
}
//Load the stored events for an AggregateID
func (c *Client) Load(aggregateID string) ([]eventhus.Event, error) {
var events []eventhus.Event
var aggregate AggregateDB
err := c.session.View(func(txn *badger.Txn) error {
item, err := txn.Get([]byte(aggregateID))
if err != nil {
return err
}
aggregateJSON, err := item.Value()
if err != nil {
return err
}
if err := json.Unmarshal(aggregateJSON, &aggregate); err != nil {
return err
}
return nil
})
if err != nil {
// events is empty in this case
return events, err
}
events = make([]eventhus.Event, len(aggregate.Events))
register := eventhus.NewEventRegister()
for i, dbEvent := range aggregate.Events {
// Create an event of the correct type.
dataType, err := register.Get(dbEvent.Type)
if err != nil {
return events, err
}
if err := json.Unmarshal(dbEvent.RawData, dataType); err != nil {
return events, err
}
// Set concrete event and zero out the decoded event.
dbEvent.data = dataType
dbEvent.RawData = []byte{}
// Translate dbEvent to eventhus.Event
events[i] = eventhus.Event{
AggregateID: aggregateID,
AggregateType: dbEvent.AggregateType,
Version: dbEvent.Version,
Type: dbEvent.Type,
Data: dbEvent.data,
}
}
return events, nil
}