What causes "create B2 client: %s" in juicedata/juicefs?

Verify keyID and applicationKey in the Backblaze B2 console / b2 CLI ('b2 authorize-account').

create B2 client: %s

Error message

create B2 client: %s

What it means

Constructing the Backblaze B2 SDK client (backblaze.NewB2) failed while initializing a B2 object storage backend. Wraps the SDK error, which typically indicates invalid or missing keyID/applicationKey credentials or an unreachable B2 API endpoint during authorization.

Source

Thrown at pkg/object/b2.go:173

// TODO: support multipart upload using S3 client

func newB2(endpoint, keyID, applicationKey, token string) (ObjectStorage, error) {
	if !strings.Contains(endpoint, "://") {
		endpoint = fmt.Sprintf("https://%s", endpoint)
	}
	uri, err := url.ParseRequestURI(endpoint)
	if err != nil {
		return nil, fmt.Errorf("Invalid endpoint: %v, error: %v", endpoint, err)
	}
	hostParts := strings.Split(uri.Host, ".")
	name := hostParts[0]
	// TODO: set UserAgent once kothar/go-backblaze supports http.Client injection
	client, err := backblaze.NewB2(backblaze.Credentials{
		KeyID:          keyID,
		ApplicationKey: applicationKey,
	})
	if err != nil {
		return nil, fmt.Errorf("create B2 client: %s", err)
	}
	client.MaxIdleUploads = 20
	bucket, err := client.Bucket(name)
	if err != nil {
		logger.Warnf("access bucket %s: %s", name, err)
	}
	if err == nil && bucket == nil {
		bucket, err = client.CreateBucket(name, "allPrivate")
		if err != nil {
			return nil, fmt.Errorf("create bucket %s: %s", name, err)
		}
	}
	if bucket == nil {
		return nil, fmt.Errorf("can't find bucket %s with provided Key ID", name)
	}
	return &b2client{bucket: bucket}, nil
}

View on GitHub (pinned to c9a67b23e8)

Solutions

Verify keyID and applicationKey in the Backblaze B2 console / b2 CLI ('b2 authorize-account').
Regenerate the application key if it was deleted or rotated.
Confirm network access to api.backblazeb2.com.
Check that keyID and applicationKey are not swapped in configuration.

Example fix

// before
keyID: "abcd", applicationKey: "00112233"   (wrong key)
// after
keyID: "003aabbccddefff0000000001", applicationKey: "K001validkey..."

Defensive patterns

Strategy: try-catch

Validate before calling

if keyID == "" || applicationKey == "" { return errors.New("B2 keyID and applicationKey are required") }

Try / catch

client, err := backblaze.NewB2(backblaze.Credentials{KeyID: keyID, ApplicationKey: applicationKey})
if err != nil {
    return fmt.Errorf("B2 authorization failed (check keyID/applicationKey and network): %w", err)
}

Prevention

Verify keys with 'b2 authorize-account' before deploying
Rotate keys via the B2 console and update config atomically
Confirm api.backblazeb2.com is reachable from the environment

When it happens

Trigger: newB2 with an application key ID or master/application key that is wrong, disabled, or revoked; network failure reaching the Backblaze auth endpoint.

Common situations: Swapped keyID/applicationKey; key deleted from Backblaze console; typo when pasting keys; corporate proxy blocking api.backblazeb2.com.

Related errors

AI-assisted analysis of juicedata/juicefs@c9a67b23e8 (2026-09-06). Data as JSON: /api/errors/8f4fb29c98e5effb. Report an issue: GitHub.