Listen to query queue (unclean)

Not finally implemented, still unclean, but functional!

cmd/query-service/main.go

 package main
 
-import "fmt"
+import (
+	"errors"
+	"fmt"
+	"os"
+	"query-service/internal/errorhandler"
+	"strconv"
+	"time"
+
+	"github.com/streadway/amqp"
+	"github.com/thijsheijden/alice"
+)
 
 func main() {
 	fmt.Println("Helloooo world")
+
+	start()
+}
+
+// Start starts consuming
+func start() {
+	// Get the unique queue id that we will be listening on
+	queueID := "aql-query-requests"
+	exchangeID := "query-requests"
+
+	// Create connection config using environment variables
+	rabbitUser := os.Getenv("RABBIT_USER")
+	rabbitPassword := os.Getenv("RABBIT_PASSWORD")
+	rabbitHost := os.Getenv("RABBIT_HOST")
+	rabbitPort, err := strconv.Atoi(os.Getenv("RABBIT_PORT"))
+
+	config := alice.CreateConfig(rabbitUser, rabbitPassword, rabbitHost, rabbitPort, true, time.Minute*1, alice.DefaultErrorHandler)
+
+	// Open connection to broker
+	conn := alice.Connect(*config)
+
+	// Declare the exchange we want to bind to
+	exchange, err := alice.CreateDefaultExchange(exchangeID, alice.Topic)
+	if err != nil {
+		errorhandler.FailWithError(err, "failed to create exchange")
+	}
+
+	// Declare the queue we will consume from
+	queue := alice.CreateQueue(exchange, queueID, true, false, true, false, nil)
+
+	// Create the consumer
+	c, err := conn.CreateConsumer(queue, "aql.user-request", alice.DefaultConsumerErrorHandler)
+	if err != nil {
+		errorhandler.FailWithError(err, "failed to create consumer")
+	}
+
+	// Start consuming messages
+	c.ConsumeMessages(nil, false, consumeMessage)
+
+	select {}
+}
+
+// Handle incoming messages, pass them to the correct place
+func consumeMessage(msg amqp.Delivery) {
+	// Look at the result type in the headers
+	switch msg.Headers["type"] {
+	case "user-request": // A schema result
+		consumeQueryRequest(&msg)
+	default:
+		errorhandler.LogError(errors.New("undefined message type sent"), "error while consuming")
+	}
+}
+
+func consumeQueryRequest(msg *amqp.Delivery) {
+	// Retrieve JSON formatted string payload from msg
+	//jsonString := string(msg.Body)
+
+	// Call convert to AQL function
+
+	// aqlQuery := "result" // TODO: this should be the result from the json to aql conversion
+
+	// execute and retrieve result
+
+	// convert result to general (node-link (?)) format
+
+	// publish converted result
 }

go.mod

 module query-service
 
 go 1.15
+
+require (
+	github.com/rs/xid v1.3.0
+	github.com/streadway/amqp v1.0.0
+	github.com/thijsheijden/alice v0.1.5
+)

go.sum

+github.com/rs/xid v1.3.0 h1:6NjYksEUlhurdVehpc7S7dk6DAmcKv8V9gG0FsVN2U4=
+github.com/rs/xid v1.3.0/go.mod h1:trrq9SKmegXys3aeAKXMUTdJsYXVwGY3RLcfgqegfbg=
+github.com/streadway/amqp v1.0.0 h1:kuuDrUJFZL1QYL9hUNuCxNObNzB0bV/ZG5jV3RWAQgo=
+github.com/streadway/amqp v1.0.0/go.mod h1:AZpEONHx3DKn8O/DFsRAY58/XVQiIPMTMB1SddzLXVw=
+github.com/thijsheijden/alice v0.1.5 h1:kOZHhLGSHMja77I/Wvd19M7nvxgEWVIJ4vk5antCKdQ=
+github.com/thijsheijden/alice v0.1.5/go.mod h1:UypS/UTucbp+fmG1JtmXGCKPnGKimAC9AgmJ8iGoLNo=

internal/errorhandler/errorhandler.go

+package errorhandler
+
+import (
+	"fmt"
+)
+
+// LogError logs an error that is not nil
+func LogError(err error, msg string) {
+	if err != nil {
+		fmt.Printf("%s: %v", msg, err)
+	}
+}
+
+// FailWithError panics if the error is not nil
+func FailWithError(err error, msg string) {
+	if err != nil {
+		fmt.Printf("%s: %v", msg, err)
+		panic(err)
+	}
+}