crowdsecurity/crowdsec · error

empty loki host

Error message

empty loki host

What it means

DSN validation in loki ConfigureByDSN: the loki:// DSN parsed successfully but u.Host is empty (e.g. 'loki:///' or 'loki:///query'). The host is the Loki server address, which is required to build the client URL; the scheme defaults to http if not overridden by query parameters.

Source

Thrown at pkg/acquisition/modules/loki/config.go:133

func (l *Source) ConfigureByDSN(_ context.Context, dsn string, labels map[string]string, logger *log.Entry, uuid string) error {
	l.logger = logger
	l.Config = Configuration{}
	l.Config.Mode = configuration.CAT_MODE
	l.Config.Labels = labels
	l.Config.UniqueId = uuid

	u, err := url.Parse(dsn)
	if err != nil {
		return fmt.Errorf("while parsing dsn '%s': %w", dsn, err)
	}

	if u.Scheme != "loki" {
		return fmt.Errorf("invalid DSN %s for loki source, must start with loki://", dsn)
	}

	if u.Host == "" {
		return errors.New("empty loki host")
	}

	scheme := "http"

	params := u.Query()
	if q := params.Get("ssl"); q != "" {
		scheme = "https"
	}

	if q := params.Get("query"); q != "" {
		l.Config.Query = q
	}

	if w := params.Get("wait_for_ready"); w != "" {
		l.Config.WaitForReady, err = time.ParseDuration(w)
		if err != nil {
			return err
		}

View on GitHub (pinned to 909b515798)

Solutions

1. Include the Loki host in the DSN, e.g. loki://localhost:3100/
2. Use loki://host:port?ssl=true for HTTPS endpoints
3. Verify the variable holding the Loki address is not empty at DSN construction

Example fix

// before
loki://?query=%7Bjob%3D%22x%22%7D
// after
loki://localhost:3100/?query=%7Bjob%3D%22x%22%7D

u, err := url.Parse(dsn)
if err != nil || u.Scheme != "loki" || u.Host == "" {
    return fmt.Errorf("invalid loki DSN: %s", dsn)
}

When it happens

Trigger: A DSN like `loki://` or `loki://?query=...` (no host before the ? or path) passed to ConfigureByDSN.

Common situations: Generating DSNs from templates where the host variable is empty, truncating the URL, or forgetting the host when adding query params.

Understand the failure class

Background: "Invalid URL" / "URL cannot be empty": fix the malformed or missing URL behind request-construction failures — this error's family across 50 libraries.

Related errors

• failed to parse DSN %s: %w
• while parsing dsn '%s': %w
• invalid DSN %s for VictoriaLogs source, must start with vict
• query is mandatory (at least start_date and end_date or back
• cloudwatch path must contain group and stream : /my/group/na

AI-assisted analysis of crowdsecurity/crowdsec@909b515798 (2026-09-06). Data as JSON: /api/errors/ffb3db550367505b. Report an issue: GitHub.