new.go

package mqs

import (
	"context"
	"fmt"
	"net/url"

	"go.opencensus.io/trace"

	"github.com/fnproject/fn/api/models"
	"github.com/sirupsen/logrus"
)

// Provider for message queue extensions
type Provider interface {
	fmt.Stringer
	//Supports indicates if this provider can handle a specific URL scheme
	Supports(url *url.URL) bool
	//New creates a new message queue from a given URL
	New(url *url.URL) (models.MessageQueue, error)
}

var mqProviders []Provider

// AddProvider registers a new global message queue provider
func AddProvider(p Provider) {
	mqProviders = append(mqProviders, p)
}

// New will parse the URL and return the correct MQ implementation.
func New(mqURL string) (models.MessageQueue, error) {
	mq, err := newmq(mqURL)
	if err != nil {
		return nil, err
	}
	return &metricMQ{mq}, nil
}

func newmq(mqURL string) (models.MessageQueue, error) {
	// Play with URL schemes here: https://play.golang.org/p/xWAf9SpCBW
	u, err := url.Parse(mqURL)
	if err != nil {
		logrus.WithError(err).WithFields(logrus.Fields{"url": mqURL}).Fatal("bad MQ URL")
	}
	logrus.WithFields(logrus.Fields{"mq": u.Scheme}).Debug("selecting MQ")
	for _, p := range mqProviders {
		if p.Supports(u) {
			return p.New(u)
		}
	}
	return nil, fmt.Errorf("mq type not supported %v", u.Scheme)
}

type metricMQ struct {
	mq models.MessageQueue
}

func (m *metricMQ) Push(ctx context.Context, t *models.Call) (*models.Call, error) {
	ctx, span := trace.StartSpan(ctx, "mq_push")
	defer span.End()
	return m.mq.Push(ctx, t)
}

func (m *metricMQ) Reserve(ctx context.Context) (*models.Call, error) {
	ctx, span := trace.StartSpan(ctx, "mq_reserve")
	defer span.End()
	return m.mq.Reserve(ctx)
}

func (m *metricMQ) Delete(ctx context.Context, t *models.Call) error {
	ctx, span := trace.StartSpan(ctx, "mq_delete")
	defer span.End()
	return m.mq.Delete(ctx, t)
}

// Close closes the underlying message queue
func (m *metricMQ) Close() error {
	return m.mq.Close()
}