Automattic/mongoose · error · MongooseError

MongoDB prohibits index creation on connections that read fr

Error message

MongoDB prohibits index creation on connections that read from non-primary replicas.  Connections that set "readPreference" to "secondary" or "secondaryPreferred" may not opt-in to the following connection options: autoCreate, autoIndex

What it means

Error "MongoDB prohibits index creation on connections that read from non-primary replicas. Connections that set "readPreference" to "secondary" or "secondaryPreferred" may not opt-in to the following connection options: autoCreate, autoIndex" thrown in Automattic/mongoose.

Source

Thrown at lib/helpers/processConnectionOptions.js:57

function setsSecondaryRead(prefString) {
  return !!(prefString === 'secondary' || prefString === 'secondaryPreferred');
}

function getUriReadPreference(connectionString) {
  const exp = /(?:&|\?)readPreference=(\w+)(?:&|$)/;
  const match = exp.exec(connectionString);
  return match ? match[1] : null;
}

function defaultIndexOptsToFalse(opts) {
  opts.config = { autoIndex: false };
  opts.autoCreate = false;
  opts.autoIndex = false;
  return opts;
}

function throwReadPreferenceError() {
  throw new MongooseError(
    'MongoDB prohibits index creation on connections that read from ' +
            'non-primary replicas.  Connections that set "readPreference" to "secondary" or ' +
            '"secondaryPreferred" may not opt-in to the following connection options: ' +
            'autoCreate, autoIndex'
  );
}

module.exports = processConnectionOptions;

View on GitHub (pinned to 49cdab0136)

When it happens

Trigger: Thrown at lib/helpers/processConnectionOptions.js:57 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of Automattic/mongoose@49cdab0136 (2026-08-21). Data as JSON: /api/errors/f1200c31db9791e3. Report an issue: GitHub.