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order_service.go
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order_service.go
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package shop
import (
"context"
"encoding/json"
"fmt"
"github.com/cloudhut/owl-shop/pkg/fake"
"github.com/cloudhut/owl-shop/pkg/kafka"
"github.com/twmb/franz-go/pkg/kerr"
"github.com/twmb/franz-go/pkg/kgo"
"github.com/twmb/franz-go/pkg/kmsg"
"go.uber.org/zap"
"google.golang.org/protobuf/proto"
"sync"
"time"
)
type OrderService struct {
cfg Config
logger *zap.Logger
kafkaSvc *kafka.Service
consumerClient *kgo.Client
bufferSize int
recentCustomersMu sync.RWMutex
recentCustomers []fake.Customer
clientID string
topicName string
topicNameProtobuf string
}
func NewOrderService(cfg Config, logger *zap.Logger) (*OrderService, error) {
clientID := cfg.GlobalPrefix + "order-service"
cfg.Kafka.ClientID = clientID
kafkaSvc, err := kafka.NewService(cfg.Kafka, logger)
if err != nil {
return nil, fmt.Errorf("failed to create kafka service: %w", err)
}
consumerClient, err := kafkaSvc.NewKafkaClient()
if err != nil {
return nil, fmt.Errorf("failed to create kafka consumer client: %w", err)
}
// This slice is used to keep some customers in the buffer so that they can be modified or deleted
bufferSize := 500
recentCustomers := make([]fake.Customer, 0, bufferSize)
return &OrderService{
cfg: cfg,
logger: logger.With(zap.String("service", "order_service")),
kafkaSvc: kafkaSvc,
consumerClient: consumerClient,
bufferSize: bufferSize,
recentCustomersMu: sync.RWMutex{},
recentCustomers: recentCustomers,
clientID: clientID,
topicName: cfg.GlobalPrefix + "orders",
topicNameProtobuf: cfg.GlobalPrefix + "orders" + "-protobuf",
}, nil
}
func (svc *OrderService) Start() {
svc.consumerClient.AssignGroup(
svc.clientID,
kgo.GroupTopics(svc.cfg.GlobalPrefix+"customers"),
kgo.AutoCommitInterval(500*time.Millisecond))
for {
ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
fetches := svc.consumerClient.PollFetches(ctx)
cancel()
errors := fetches.Errors()
if errors != nil {
svc.logger.Warn("failed to poll fetches", zap.Error(errors[0].Err))
}
iter := fetches.RecordIter()
for !iter.Done() {
rec := iter.Next()
kafkaMessagesConsumedTotal.With(map[string]string{"event_type": EventTypeCustomerConsumed}).Inc()
if rec.Value == nil {
continue
}
customer := fake.Customer{}
err := json.Unmarshal(rec.Value, &customer)
if err != nil {
// Skip message
svc.logger.Warn("failed to deserialize customer", zap.Error(err))
continue
}
svc.recentCustomersMu.Lock()
if len(svc.recentCustomers) < svc.bufferSize {
svc.recentCustomers = append(svc.recentCustomers, customer)
}
svc.recentCustomersMu.Unlock()
}
}
}
func (svc *OrderService) Initialize(ctx context.Context) error {
svc.logger.Info("initializing order service")
// 1. Test kafka connectivity
metadata, err := svc.kafkaSvc.GetMetadata(ctx)
if err != nil {
return fmt.Errorf("failed to get metadata to test kafka connectivity: %w", err)
}
// 2. Ensure that the Kafka topic exists
isTopicExistent := false
for _, topic := range metadata.Topics {
if topic.Topic == svc.topicName {
isTopicExistent = true
break
}
}
if !isTopicExistent {
err := svc.createKafkaTopic(ctx)
if err != nil {
return fmt.Errorf("failed to create kafka topic '%v': %w", svc.topicName, err)
}
svc.logger.Info("successfully created Kafka topic", zap.String("topic_name", svc.topicName))
}
return nil
}
func (svc *OrderService) CreateOrder() {
customer, err := svc.popCustomerFromBuffer()
if err != nil {
svc.logger.Debug("failed to pop customer from buffer", zap.Error(err))
return
}
order := fake.NewOrder(customer)
err = svc.produceOrderJSON(order)
if err != nil {
svc.logger.Warn("failed to produce order (json)", zap.Error(err))
return
}
err = svc.produceOrderProtobuf(order)
if err != nil {
svc.logger.Warn("failed to produce order (protobuf)", zap.Error(err))
return
}
kafkaMessagesProducedTotal.With(map[string]string{"event_type": EventTypeOrderCreated}).Add(2)
return
}
func (svc *OrderService) produceOrderJSON(order fake.Order) error {
serialized, err := kafka.SerializeJson(order)
if err != nil {
return fmt.Errorf("failed to serialize customer struct: %w", err)
}
rec := kgo.Record{
Key: []byte(order.ID),
Value: serialized,
Headers: []kgo.RecordHeader{{Key: "revision", Value: []byte("0")}},
Timestamp: time.Now(),
Topic: svc.topicName,
}
ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
defer cancel()
err = svc.kafkaSvc.KafkaClient.Produce(ctx, &rec, func(rec *kgo.Record, err error) {
if err != nil {
svc.logger.Error("failed to produce record",
zap.String("topic_name", rec.Topic),
zap.Error(err),
)
return
}
})
if err != nil {
return fmt.Errorf("failed to produce: %w", err)
}
return nil
}
func (svc *OrderService) produceOrderProtobuf(order fake.Order) error {
pbOrder := order.Protobuf()
serialized, err := proto.Marshal(pbOrder)
if err != nil {
return fmt.Errorf("failed to serialize customer struct: %w", err)
}
rec := kgo.Record{
Key: []byte(order.ID),
Value: serialized,
Headers: []kgo.RecordHeader{
{Key: "revision", Value: []byte("0")},
{Key: "proto_message_type", Value: []byte("Order")},
},
Timestamp: time.Now(),
Topic: svc.topicNameProtobuf,
}
ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
defer cancel()
err = svc.kafkaSvc.KafkaClient.Produce(ctx, &rec, func(rec *kgo.Record, err error) {
if err != nil {
svc.logger.Error("failed to produce record",
zap.String("topic_name", rec.Topic),
zap.Error(err),
)
return
}
})
if err != nil {
return fmt.Errorf("failed to produce: %w", err)
}
return nil
}
func (svc *OrderService) popCustomerFromBuffer() (fake.Customer, error) {
svc.recentCustomersMu.Lock()
defer svc.recentCustomersMu.Unlock()
if len(svc.recentCustomers) == 0 {
// No customers in buffer yet
return fake.Customer{}, fmt.Errorf("buffer is empty")
}
customer := svc.recentCustomers[0]
svc.recentCustomers = svc.recentCustomers[1:]
return customer, nil
}
func (svc *OrderService) createKafkaTopic(ctx context.Context) error {
cleanupPolicy := "compact"
req := kmsg.CreateTopicsRequest{
Topics: []kmsg.CreateTopicsRequestTopic{
// Normal Topic for JSON
{
Topic: svc.topicName,
NumPartitions: 6,
ReplicationFactor: svc.cfg.Kafka.TopicReplicationFactor,
Configs: []kmsg.CreateTopicsRequestTopicConfig{
{"cleanup.policy", &cleanupPolicy},
},
},
// Protobuf serialized orders go into a separate topic
{
Topic: svc.topicNameProtobuf,
NumPartitions: 6,
ReplicationFactor: svc.cfg.Kafka.TopicReplicationFactor,
Configs: []kmsg.CreateTopicsRequestTopicConfig{
{"cleanup.policy", &cleanupPolicy},
},
},
},
TimeoutMillis: 60 * 1000,
}
res, err := req.RequestWith(ctx, svc.kafkaSvc.KafkaClient)
if err != nil {
return fmt.Errorf("create topics request failed: %w", err)
}
// Check for inner kafka errors
if len(res.Topics) != 2 {
return fmt.Errorf("unexpected topic response count from create topics request. Expected count '2', actual returned count: '%v'", len(res.Topics))
}
err = kerr.ErrorForCode(res.Topics[0].ErrorCode)
if err != nil {
return fmt.Errorf("create topics request failed. Inner kafka error: %w", err)
}
err = kerr.ErrorForCode(res.Topics[1].ErrorCode)
if err != nil {
return fmt.Errorf("create topics request failed. Inner kafka error: %w", err)
}
return nil
}