What causes "while parsing dsn '%s': %w" in crowdsecurity/crowdsec?

Inspect the wrapped url.Parse error to find the offending character and escape or remove it (e.g. use %20 for spaces).

while parsing dsn '%s': %w

Error message

while parsing dsn '%s': %w

What it means

ConfigureByDSN failed when url.Parse could not interpret the DSN string. The DSN passed via -type victorialogs acquisition (e.g. on cscli or acquis DSN) is not a parseable URL, so the source cannot derive its configuration.

Source

Thrown at pkg/acquisition/modules/victorialogs/config.go:126

		FailMaxDuration: s.Config.MaxFailureDuration,
	}

	s.Client = vlclient.NewVLClient(clientConfig)
	s.Client.Logger = logger.WithFields(log.Fields{"component": "victorialogs-client", "source": s.Config.URL})

	return nil
}

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

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

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

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

	scheme := "http"

	params := u.Query()

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

View on GitHub (pinned to 909b515798)

Solutions

Inspect the wrapped url.Parse error to find the offending character and escape or remove it (e.g. use %20 for spaces).
Rewrite the DSN in the standard form victorialogs://host:port with proper URL escaping.
Quote the DSN in YAML and check for stray whitespace or line breaks introduced by copy-paste.

Example fix

// before
victorialogs://vl host:9428  # space breaks url.Parse

// after
victorialogs://vl-host:9428

Defensive patterns

Strategy: validation

Validate before calling

if _, err := url.Parse(dsn); err != nil {
    return fmt.Errorf("malformed DSN %q: %w", dsn, err)
}

Try / catch

u, err := url.Parse(dsn)
if err != nil {
    log.Errorf("bad DSN %q: %v", dsn, err)
    return err
}

Prevention

URL-escape special characters when composing DSNs.
Trim whitespace/newlines from DSN strings sourced from shell or docs.
Quote DSNs in YAML files.

When it happens

Trigger: A DSN string like 'victorialogs://host:port' contains characters illegal in a URL (unescaped spaces, stray '%', control chars) making url.Parse return an error.

Common situations: Pasting a DSN with a trailing space or newline from a shell/docs; unescaped special characters in a password or query embedded in the DSN; quoting mistakes in acquis.yaml leaving raw '%' sequences.

Understand the failure class

Background: "Invalid URL" errors: why new URL(), URI.parse, and reqwest::Url reject your string — missing scheme, whitespace, and bad path format — this error's family across 39 libraries.

Related errors

AI-assisted analysis of crowdsecurity/crowdsec@909b515798 (2026-09-06). Data as JSON: /api/errors/9aeeb2139c12eeff. Report an issue: GitHub.