README
¶
event source
golang event sourcing library
Installation
go get github.com/savaki/eventsource
Example
package main
import (
"context"
"fmt"
"log"
"time"
"github.com/savaki/eventsource"
)
// UserCreated defines a user creation event
type UserCreated struct {
eventsource.Model
}
// UserFirstSet defines an event by simple struct embedding
type UserNameSet struct {
eventsource.Model
Name string
}
// UserLastSet implements the eventsource.Event interface directly
type UserEmailSet struct {
ID string
Version int
At time.Time
Email string
}
func (m UserEmailSet) AggregateID() string {
return m.ID
}
func (m UserEmailSet) EventVersion() int {
return m.Version
}
func (m UserEmailSet) EventAt() time.Time {
return m.At
}
type User struct {
ID string
Version int
Name string
Email string
}
func (item *User) On(event eventsource.Event) bool {
switch v := event.(type) {
case *UserCreated:
item.Version = v.Model.Version
item.ID = v.Model.ID
case *UserNameSet:
item.Version = v.Model.Version
item.Name = v.Name
case *UserEmailSet:
item.Version = v.Version
item.Email = v.Email
default:
return false
}
return true
}
func main() {
userEvents := eventsource.New(&User{})
err := userEvents.Bind(
UserCreated{},
UserNameSet{},
UserEmailSet{},
)
if err != nil {
log.Fatalln(err)
}
id := "123"
setNameEvent := &UserNameSet{
Model: eventsource.Model{ID: id, Version: 1},
Name: "Joe Public",
}
setEmailEvent := &UserEmailSet{
ID: id,
Version: 2,
Email: "joe.public@example.com",
}
ctx := context.Background()
err = userEvents.Save(ctx, setEmailEvent, setNameEvent)
if err != nil {
log.Fatalln(err)
}
v, err := userEvents.Load(ctx, id)
if err != nil {
log.Fatalln(err)
}
user := v.(*User)
fmt.Printf("Hello %v %v\n", user.Name, user.Email) // prints "Hello Joe Public joe.public@example.com"
}
Documentation
¶
Index ¶
Constants ¶
const ( AggregateNil = "AggregateNil" DuplicateID = "DuplicateID" DuplicateVersion = "DuplicateVersion" DuplicateAt = "DuplicateAt" DuplicateType = "DuplicateType" InvalidID = "InvalidID" InvalidAt = "InvalidAt" InvalidVersion = "InvalidVersion" InvalidEncoding = "InvalidEncoding" UnboundEventType = "UnboundEventType" AggregateNotFound = "AggregateNotFound" UnhandledEvent = "UnhandledEvent" )
Variables ¶
This section is empty.
Functions ¶
Types ¶
type Aggregate ¶
type Aggregate interface {
// On will be called for each event processed; returns true if aggregate was able to handle the event, false otherwise
On(event Event) bool
}
Aggregate represents the aggregate root in the domain driven design sense. It aggregates the events and presents the current view of the domain object
type EpochMillis ¶
type EpochMillis int64
EpochMillis represents the number of millis since Jan 1, 1970
func Time ¶
func Time(t time.Time) EpochMillis
Time converts a time.Time to an EpochMillis ; units of time less than millis are lost
func (EpochMillis) Int64 ¶
func (e EpochMillis) Int64() int64
Int64 converts EpochMillis to int64 representation
func (EpochMillis) String ¶
func (e EpochMillis) String() string
String represents EpochMillis as a numeric string
func (EpochMillis) Time ¶
func (e EpochMillis) Time() time.Time
Time converts EpochMillis to an instance of time.Time
type Error ¶
type Error interface {
error
// Returns the original error if one was set. Nil is returned if not set.
Cause() error
// Returns the short phrase depicting the classification of the error.
Code() string
// Returns the error details message.
Message() string
}
Error provides a standardized error interface for eventsource
type Event ¶
type Event interface {
// AggregateID returns the aggregate id of the event
AggregateID() string
// Version contains version number of aggregate
EventVersion() int
// At indicates when the event took place
EventAt() time.Time
}
Event describes a change that happened to the aggregate.
* Past tense, EmailChanged * Contains intent, EmailChanged is better than EmailSet
type EventTyper ¶
type EventTyper interface {
// EventType returns the name of event type
EventType() string
}
EventTyper is an optional interface that can be applied to an Event that allows it to specify an event type different than the name of the struct
type History ¶
type History []Record
History represents the events to be applied to recreate the aggregate in version order
type Model ¶
type Model struct {
// ID contains the AggregateID
ID string
// Version holds the event version
Version int
// At contains the event time
At time.Time
}
Model provides a default implementation of an Event that is suitable for being embedded
func (Model) AggregateID ¶
AggregateID implements part of the Event interface
func (Model) EventVersion ¶
EventVersion implements part of the Event interface
type Option ¶
type Option func(registry *repository)
func WithSerializer ¶
func WithSerializer(serializer Serializer) Option
type Record ¶
type Record struct {
// Version is the event version the Data represents
Version int
// At indicates when the event happened; provided as a utility for the store
At EpochMillis
// Data contains the Serializer encoded version of the data
Data []byte
}
Record provides the shape of the records to be saved to the db
type Repository ¶
type Repository interface {
Bind(events ...Event) error
Load(ctx context.Context, aggregateID string) (Aggregate, error)
Save(ctx context.Context, events ...Event) error
New() Aggregate
}
func New ¶
func New(prototype Aggregate, opts ...Option) Repository
type Serializer ¶
type Serializer interface {
Bind(events ...Event) error
Serialize(event Event) (Record, error)
Deserialize(record Record) (Event, error)
}
func JSONSerializer ¶
func JSONSerializer() Serializer
type Store ¶
type Store interface {
// Save saves events to the store
Save(ctx context.Context, aggregateID string, records ...Record) error
// Fetch retrieves the History of events with the specified aggregate id
Fetch(ctx context.Context, aggregateID string, version int) (History, error)
}
Store provides storage for events
Source Files
Directories