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main.go
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main.go
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package main
import (
"encoding/json"
"flag"
"log"
"net/http"
"time"
memdb "github.com/hashicorp/go-memdb"
"github.com/nats-io/nats"
)
type productInsertedEvent struct {
Name string `json:"name"`
SKU string `json:"sku"`
}
type product struct {
Name string `json:"name"`
Code string `json:"code"`
LastUpdated string `json:"last_updated"`
}
func (p product) FromProductInsertedEvent(e productInsertedEvent) product {
p.Name = e.Name
p.Code = e.SKU
p.LastUpdated = time.Now().Format(time.RFC3339)
return p
}
var schema *memdb.DBSchema
var db *memdb.MemDB
var natsClient *nats.Conn
var natsServer = flag.String("nats", "", "NATS server URI")
func init() {
flag.Parse()
schema = &memdb.DBSchema{
Tables: map[string]*memdb.TableSchema{
"product": &memdb.TableSchema{
Name: "product",
Indexes: map[string]*memdb.IndexSchema{
"id": &memdb.IndexSchema{
Name: "id",
Unique: true,
Indexer: &memdb.StringFieldIndex{Field: "SKU"},
},
},
},
},
}
err := schema.Validate()
if err != nil {
log.Fatal(err)
}
db, err = memdb.NewMemDB(schema)
if err != nil {
log.Fatal(err)
}
natsClient, err = nats.Connect("nats://" + *natsServer)
if err != nil {
log.Fatal(err)
}
}
func main() {
log.Println("Subscribing to events")
natsClient.Subscribe("product.inserted", func(m *nats.Msg) {
log.Println("New event")
productMessage(m)
})
http.DefaultServeMux.HandleFunc("/product", getProducts)
log.Println("Starting product read service on port 8081")
log.Fatal(http.ListenAndServe(":8081", http.DefaultServeMux))
}
func getProducts(rw http.ResponseWriter, r *http.Request) {
log.Println("/get handler called")
txn := db.Txn(false)
results, err := txn.Get("product", "id")
if err != nil {
log.Println(err)
rw.WriteHeader(http.StatusInternalServerError)
return
}
products := make([]product, 0)
for {
obj := results.Next()
if obj == nil {
break
}
products = append(products, obj.(product))
}
encoder := json.NewEncoder(rw)
encoder.Encode(products)
}
func productMessage(m *nats.Msg) {
pie := productInsertedEvent{}
err := json.Unmarshal(m.Data, &pie)
if err != nil {
log.Println("Unable to unmarshal event object")
return
}
p := product{}.FromProductInsertedEvent(pie)
txn := db.Txn(true)
if err := txn.Insert("product", p); err != nil {
log.Println(err)
return
}
txn.Commit()
log.Println("Saved product: ", p)
}