Environment variable substitution for DSN's #427
Description
Is your feature request related to a problem? Please describe.
When using a DSN that contains environment variable placeholders (e.g., ${DB_USER}), the placeholders are not automatically substituted, which prevents us from reusing existing database secrets.
Describe the solution you'd like
I suggest enhancing the safeParse function to automatically substitute environment variable placeholders within the DSN, utilizing the newly introduced functionality for setting environment variables in PR #399.
func safeParse(rawURL string) (*dburl.URL, error) {
parsed, err := dburl.Parse(os.ExpandEnv(rawURL))
if err != nil {
if uerr := new(url.Error); errors.As(err, &uerr) {
return nil, uerr.Err
}
return nil, errors.New("invalid URL")
}
return parsed, nil
}Describe alternatives you've considered
We are currently implementing the SQL exporter jobs functionality, allowing us to use a single exporter instance against multiple database connections. However, we don't see suitable and safe solutions for setting the database credentials except running two SQL exporter instances with the SQLEXPORTER_TARGET_DSN set. This approach would require creating a new secret with the DSN value, while a secret with the username and password for the databases already exists.
Feature request #186 will partially resolve this issue, but would still require two instances.