forked from looplab/eventhorizon
/
eventstore.go
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/
eventstore.go
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// Copyright (c) 2021 - The Event Horizon authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package mongodb_v2
import (
"context"
"fmt"
"time"
"go.mongodb.org/mongo-driver/bson"
"go.mongodb.org/mongo-driver/mongo"
mongoOptions "go.mongodb.org/mongo-driver/mongo/options"
"go.mongodb.org/mongo-driver/mongo/readconcern"
"go.mongodb.org/mongo-driver/mongo/readpref"
"go.mongodb.org/mongo-driver/mongo/writeconcern"
// Register uuid.UUID as BSON type.
_ "github.com/looplab/eventhorizon/codec/bson"
eh "github.com/looplab/eventhorizon"
"github.com/looplab/eventhorizon/uuid"
)
// EventStore is an eventhorizon.EventStore for MongoDB, using one collection
// for all events and another to keep track of all aggregates/streams. It also
// keep tracks of the global position of events, stored as metadata.
type EventStore struct {
client *mongo.Client
events *mongo.Collection
streams *mongo.Collection
eventHandler eh.EventHandler
}
// NewEventStore creates a new EventStore with a MongoDB URI: `mongodb://hostname`.
func NewEventStore(uri, dbName string, options ...Option) (*EventStore, error) {
opts := mongoOptions.Client().ApplyURI(uri)
opts.SetWriteConcern(writeconcern.New(writeconcern.WMajority()))
opts.SetReadConcern(readconcern.Majority())
opts.SetReadPreference(readpref.Primary())
client, err := mongo.Connect(context.TODO(), opts)
if err != nil {
return nil, fmt.Errorf("could not connect to DB: %w", err)
}
return NewEventStoreWithClient(client, dbName, options...)
}
// NewEventStoreWithClient creates a new EventStore with a client.
func NewEventStoreWithClient(client *mongo.Client, dbName string, options ...Option) (*EventStore, error) {
if client == nil {
return nil, fmt.Errorf("missing DB client")
}
db := client.Database(dbName)
s := &EventStore{
client: client,
events: db.Collection("events"),
streams: db.Collection("streams"),
}
for _, option := range options {
if err := option(s); err != nil {
return nil, fmt.Errorf("error while applying option: %w", err)
}
}
ctx := context.Background()
if _, err := s.events.Indexes().CreateOne(ctx, mongo.IndexModel{
Keys: bson.M{"aggregate_id": 1},
}); err != nil {
return nil, fmt.Errorf("could not ensure events index: %w", err)
}
// Make sure the $all stream exists.
if err := s.streams.FindOne(ctx, bson.M{
"_id": "$all",
}).Err(); err == mongo.ErrNoDocuments {
if _, err := s.streams.InsertOne(ctx, bson.M{
"_id": "$all",
"position": 0,
}); err != nil {
return nil, fmt.Errorf("could not create the $all stream document: %w", err)
}
} else if err != nil {
return nil, fmt.Errorf("could not find the $all stream document: %w", err)
}
return s, nil
}
// Option is an option setter used to configure creation.
type Option func(*EventStore) error
// WithEventHandler adds an event handler that will be called when saving events.
// An example would be to add an event bus to publish events.
func WithEventHandler(h eh.EventHandler) Option {
return func(s *EventStore) error {
s.eventHandler = h
return nil
}
}
// Save implements the Save method of the eventhorizon.EventStore interface.
func (s *EventStore) Save(ctx context.Context, events []eh.Event, originalVersion int) error {
if len(events) == 0 {
return eh.EventStoreError{
Err: eh.ErrNoEventsToAppend,
}
}
// Build all event records, with incrementing versions starting from the
// original aggregate version.
dbEvents := make([]interface{}, len(events))
aggregateID := events[0].AggregateID()
for i, event := range events {
// Only accept events belonging to the same aggregate.
if event.AggregateID() != aggregateID {
return eh.EventStoreError{
Err: eh.ErrInvalidEvent,
}
}
// Only accept events that apply to the correct aggregate version.
if event.Version() != originalVersion+i+1 {
return eh.EventStoreError{
Err: eh.ErrIncorrectEventVersion,
}
}
// Create the event record for the DB.
e, err := newEvt(ctx, event)
if err != nil {
return err
}
dbEvents[i] = e
}
sess, err := s.client.StartSession(nil)
if err != nil {
return eh.EventStoreError{
Err: eh.ErrCouldNotSaveEvents,
BaseErr: err,
}
}
defer sess.EndSession(ctx)
if _, err := sess.WithTransaction(ctx, func(txCtx mongo.SessionContext) (interface{}, error) {
// Fetch and increment global version in the all-stream.
r := s.streams.FindOneAndUpdate(txCtx,
bson.M{"_id": "$all"},
bson.M{"$inc": bson.M{"position": len(dbEvents)}},
)
if r.Err() != nil {
return nil, fmt.Errorf("could not increment global position: %w", r.Err())
}
allStream := struct {
Position int
}{}
if err := r.Decode(&allStream); err != nil {
return nil, fmt.Errorf("could not decode global position: %w", err)
}
// Use the global position as ID for the stored events.
// This natively prevents duplicate events to be written.
var strm *stream
for i, e := range dbEvents {
event := e.(*evt)
event.Position = allStream.Position + i + 1
// Also store the position in the event metadata.
event.Metadata["position"] = event.Position
// Use the last event to set the new stream position.
if i == len(dbEvents)-1 {
strm = &stream{
ID: event.AggregateID,
Position: event.Position,
AggregateType: event.AggregateType,
Version: event.Version,
UpdatedAt: event.Timestamp,
}
}
}
// Store events.
insert, err := s.events.InsertMany(txCtx, dbEvents)
if err != nil {
return nil, fmt.Errorf("could not insert events: %w", err)
}
// Check that all inserted events got the requested ID (position),
// instead of a generated ID by MongoDB.
for _, e := range dbEvents {
event := e.(*evt)
found := false
for _, id := range insert.InsertedIDs {
if pos, ok := id.(int32); ok && event.Position == int(pos) {
found = true
break
}
}
if !found {
return nil, fmt.Errorf("inserted event %s at pos %d not found",
event.AggregateID, event.Position)
}
}
// Update the stream.
if originalVersion == 0 {
if _, err := s.streams.InsertOne(txCtx, strm); err != nil {
return nil, fmt.Errorf("could not insert stream: %w", err)
}
} else {
if res := s.streams.FindOneAndUpdate(txCtx,
bson.M{"_id": strm.ID},
bson.M{
"$set": bson.M{
"position": strm.Position,
"version": strm.Version,
"updated_at": strm.UpdatedAt,
},
},
mongoOptions.FindOneAndUpdate().SetUpsert(true),
); res.Err() != nil {
return nil, fmt.Errorf("could not update stream: %w", res.Err())
}
}
return nil, nil
}); err != nil {
return eh.EventStoreError{
Err: eh.ErrCouldNotSaveEvents,
BaseErr: err,
}
}
// Let the optional event handler handle the events.
if s.eventHandler != nil {
for _, e := range events {
if err := s.eventHandler.HandleEvent(ctx, e); err != nil {
return eh.CouldNotHandleEventError{
Err: err,
Event: e,
}
}
}
}
return nil
}
// Load implements the Load method of the eventhorizon.EventStore interface.
func (s *EventStore) Load(ctx context.Context, id uuid.UUID) ([]eh.Event, error) {
cursor, err := s.events.Find(ctx, bson.M{"aggregate_id": id})
if err != nil {
return nil, eh.EventStoreError{
Err: fmt.Errorf("could not find event: %w", err),
}
}
var events []eh.Event
for cursor.Next(ctx) {
var e evt
if err := cursor.Decode(&e); err != nil {
return nil, eh.EventStoreError{
Err: fmt.Errorf("could not decode event: %w", err),
}
}
// Create an event of the correct type and decode from raw BSON.
if len(e.RawData) > 0 {
var err error
if e.data, err = eh.CreateEventData(e.EventType); err != nil {
return nil, eh.EventStoreError{
Err: fmt.Errorf("could not create event data: %w", err),
}
}
if err := bson.Unmarshal(e.RawData, e.data); err != nil {
return nil, eh.EventStoreError{
Err: fmt.Errorf("could not unmarshal event data: %w", err),
}
}
e.RawData = nil
}
event := eh.NewEvent(
e.EventType,
e.data,
e.Timestamp,
eh.ForAggregate(
e.AggregateType,
e.AggregateID,
e.Version,
),
eh.WithMetadata(e.Metadata),
)
events = append(events, event)
}
return events, nil
}
// Close closes the database client.
func (s *EventStore) Close(ctx context.Context) error {
if err := s.client.Disconnect(ctx); err != nil {
return fmt.Errorf("could not close DB connection: %w", err)
}
return nil
}
// stream is a stream of events, often containing the events for an aggregate.
type stream struct {
ID uuid.UUID `bson:"_id"`
Position int `bson:"position"`
AggregateType eh.AggregateType `bson:"aggregate_type"`
Version int `bson:"version"`
UpdatedAt time.Time `bson:"updated_at"`
}
// evt is the internal event record for the MongoDB event store used
// to save and load events from the DB.
type evt struct {
Position int `bson:"_id"`
EventType eh.EventType `bson:"event_type"`
Timestamp time.Time `bson:"timestamp"`
AggregateType eh.AggregateType `bson:"aggregate_type"`
AggregateID uuid.UUID `bson:"aggregate_id"`
Version int `bson:"version"`
RawData bson.Raw `bson:"data,omitempty"`
data eh.EventData `bson:"-"`
Metadata map[string]interface{} `bson:"metadata"`
}
// newEvt returns a new evt for an event.
func newEvt(ctx context.Context, event eh.Event) (*evt, error) {
e := &evt{
EventType: event.EventType(),
Timestamp: event.Timestamp(),
AggregateType: event.AggregateType(),
AggregateID: event.AggregateID(),
Version: event.Version(),
Metadata: event.Metadata(),
}
if e.Metadata == nil {
e.Metadata = map[string]interface{}{}
}
// Marshal event data if there is any.
if event.Data() != nil {
var err error
e.RawData, err = bson.Marshal(event.Data())
if err != nil {
return nil, eh.EventStoreError{
Err: fmt.Errorf("could not marshal event data: %w", err),
}
}
}
return e, nil
}