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main.go
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main.go
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package main
import (
"context"
"database/sql"
"encoding/json"
"flag"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/aws/aws-sdk-go/service/sqs"
"github.com/dm03514/grokking-go/service-level-tests-in-action/deposits"
sqsin "github.com/dm03514/grokking-go/service-level-tests-in-action/sqs"
"github.com/lib/pq"
_ "github.com/lib/pq"
log "github.com/sirupsen/logrus"
)
func init() {
// Log as JSON instead of the default ASCII formatter.
log.SetFormatter(&log.JSONFormatter{})
// Output to stdout instead of the default stderr // Can be any io.Writer, see below for File example log.SetOutput(os.Stdout)
// Only log the warning severity or above.
log.SetLevel(log.DebugLevel)
}
const postgresDuplicateKeyErrorCode = "23505"
type MessageProcessor struct {
svc *sqs.SQS
db *sql.DB
inQueueURL string
outQueueURL string
}
func (p MessageProcessor) Process(msg *sqs.Message) error {
log.WithFields(log.Fields{
"sqs.message": msg,
}).Debug("received_message")
// do some work
// ie write to database
var d deposits.Deposit
if err := json.Unmarshal([]byte(*msg.Body), &d); err != nil {
return err
}
log.WithFields(log.Fields{
"deposit": d,
}).Debug("deserialized_deposit")
err := p.db.QueryRow(
`INSERT
INTO deposits(transaction_id, account_number, amount_cents)
VALUES($1, $2, $3) ON CONFLICT DO NOTHING RETURNING id`,
d.TransactionID, d.AccountNumber, d.AmountCents).Scan(&d.ID)
log.WithFields(log.Fields{
"deposit": d,
}).Debug("inserted_deposit")
if err, ok := err.(*pq.Error); ok && err.Code != postgresDuplicateKeyErrorCode {
return err
} else if err != nil {
return err
}
bs, err := json.Marshal(d)
if err != nil {
return err
}
sendResult, err := p.svc.SendMessage(&sqs.SendMessageInput{
MessageBody: aws.String(string(bs)),
QueueUrl: aws.String(p.outQueueURL),
DelaySeconds: aws.Int64(0),
})
if err != nil {
return err
}
// write output message
log.WithFields(log.Fields{
"deposit_sent": d,
"sqs.message": *sendResult.MessageId,
"output_queue": p.outQueueURL,
}).Debug("sent_message")
// delete message
resultDelete, err := p.svc.DeleteMessage(&sqs.DeleteMessageInput{
QueueUrl: aws.String(p.inQueueURL),
ReceiptHandle: msg.ReceiptHandle,
})
if err != nil {
return err
}
log.WithFields(log.Fields{
"sqs.message": resultDelete,
}).Debug("message_deleted")
return nil
}
func main() {
var sqsEndpointURL = flag.String("sqs-endpoint-url", "", "")
var inQueueURL = flag.String("sqs-input-url", "", "")
var outQueueURL = flag.String("sqs-output-url", "", "")
var dbConnectionString = flag.String("db-connection-string", "", "")
flag.Parse()
log.WithFields(log.Fields{
"sqs_endpoint_url": sqsEndpointURL,
"sqs_in_queue_url": inQueueURL,
"sqs_out_queue_url": outQueueURL,
"db_connection_string": dbConnectionString,
}).Info("initializing")
// connect to postgres
db, err := sql.Open("postgres", *dbConnectionString)
if err != nil {
panic(err)
}
if err = db.Ping(); err != nil {
panic(err)
}
// connect to sqs
sess := session.Must(session.NewSessionWithOptions(session.Options{
Config: aws.Config{
Endpoint: aws.String(*sqsEndpointURL),
},
SharedConfigState: session.SharedConfigEnable,
}))
svc := sqs.New(sess)
mp := MessageProcessor{
svc: svc,
db: db,
inQueueURL: *inQueueURL,
outQueueURL: *outQueueURL,
}
// read a message
inmessages := sqsin.Messages(context.Background(), svc, *inQueueURL)
log.Debugf("Entering Receive Message Loop")
for {
select {
case msg := <-inmessages:
if err := mp.Process(msg); err != nil {
panic(err)
}
}
}
}