s3blob.go

package s3blob

import (
	"context"
	"errors"
	"fmt"
	"github.com/aaronland/go-aws-session"
	aws_session "github.com/aws/aws-sdk-go/aws/session"
	"gocloud.dev/blob"
	gc_s3blob "gocloud.dev/blob/s3blob"
	"net/url"
	"strings"
	"sync"
)

const Scheme = "s3blob"

func init() {
	blob.DefaultURLMux().RegisterBucket(Scheme, new(lazySessionOpener))
}

type URLOpener struct {
	Session *aws_session.Session
}

type lazySessionOpener struct {
	init   sync.Once
	opener *URLOpener
	err    error
}

func (o *lazySessionOpener) OpenBucketURL(ctx context.Context, u *url.URL) (*blob.Bucket, error) {

	o.init.Do(func() {

		query := u.Query()

		dsn := make([]string, 0)

		for k, v := range query {

			if len(v) != 1 {
				o.err = errors.New("Invalid DSN value")
				return
			}

			dsn = append(dsn, fmt.Sprintf("%s=%s", k, v[0]))
		}

		str_dsn := strings.Join(dsn, " ")

		sess, err := session.NewSessionWithDSN(str_dsn)

		if err != nil {
			o.err = err
			return
		}

		o.opener = &URLOpener{
			Session: sess,
		}
	})

	if o.err != nil {
		return nil, fmt.Errorf("open bucket %v: %v", u, o.err)
	}

	return o.opener.OpenBucketURL(ctx, u)
}

func (o *URLOpener) OpenBucketURL(ctx context.Context, u *url.URL) (*blob.Bucket, error) {
	return gc_s3blob.OpenBucket(ctx, o.Session, u.Host, nil)
}