mongodb/node-mongodb-native · error · MongoParseError

Cannot use srvMaxHosts or srvServiceName with a non-srv…

Error message

Cannot use srvMaxHosts or srvServiceName with a non-srv connection string

What it means

Thrown by MongoParseError (else branch at src/connection_string.ts:494) when the URI is plain `mongodb://` (not +srv) but the user supplied `srvMaxHosts` or `srvServiceName`. Those options only have meaning for SRV record resolution, so a non-SRV connection has nothing for them to do.

Solutions

1. Switch the URI scheme to `mongodb+srv://` if you want SRV-record-driven discovery.
2. Otherwise remove `srvMaxHosts` and `srvServiceName` from both the URI query string and the options object.

Example fix

// before
new MongoClient('mongodb://host1:27017,host2:27017/?srvMaxHosts=2')

// after (plain mongodb, no srv option)
new MongoClient('mongodb://host1:27017,host2:27017/')

function assertSrvOptionsMatchScheme(uri, options = {}) {
  const isSrv = uri.startsWith('mongodb+srv://');
  if (!isSrv && (options.srvMaxHosts != null || options.srvServiceName || /[?&]srv(MaxHosts|ServiceName)=/.test(uri))) {
    throw new Error('srvMaxHosts / srvServiceName require a mongodb+srv:// URI.');
  }
}

try { new MongoClient(uri, options); } catch (e) { if (e instanceof MongoParseError && /srvMaxHosts or srvServiceName with a non-srv/.test(e.message)) { delete options.srvMaxHosts; delete options.srvServiceName; } else throw e; }

When it happens

Trigger: `mongodb://host1:27017,host2:27017/?srvMaxHosts=2`, or `mongodb://host:27017/?srvServiceName=_tcp.example.com`, or passing either option via the options object with a plain mongodb:// URI.

Common situations: Switching a URI from `mongodb+srv://` to `mongodb://` but forgetting to drop the srv-only options; sharing an options object across srv and non-srv clients.

Related errors

• Cannot limit srv hosts with loadBalanced enabled
• Cannot use srvMaxHosts option with replicaSet
• SRV URI does not support directConnection
• Cannot combine replicaSet option with srvMaxHosts
• Cannot have empty URI params in DNS TXT Record

AI-assisted analysis of mongodb/node-mongodb-native@dce7939f86 (2026-08-11). Data as JSON: /api/errors/f6c55f83fb5dbf71. Report an issue: GitHub.

Appendix: source

Thrown at src/connection_string.ts:494

    if (mongoOptions.srvMaxHosts > 0 && typeof mongoOptions.replicaSet === 'string') {
      throw new MongoParseError('Cannot use srvMaxHosts option with replicaSet');
    }

    // SRV turns on TLS by default, but users can override and turn it off
    const noUserSpecifiedTLS = !objectOptions.has('tls') && !urlOptions.has('tls');
    const noUserSpecifiedSSL = !objectOptions.has('ssl') && !urlOptions.has('ssl');
    if (noUserSpecifiedTLS && noUserSpecifiedSSL) {
      mongoOptions.tls = true;
    }
  } else {
    const userSpecifiedSrvOptions =
      urlOptions.has('srvMaxHosts') ||
      objectOptions.has('srvMaxHosts') ||
      urlOptions.has('srvServiceName') ||
      objectOptions.has('srvServiceName');

    if (userSpecifiedSrvOptions) {
      throw new MongoParseError(
        'Cannot use srvMaxHosts or srvServiceName with a non-srv connection string'
      );
    }
  }

  if (mongoOptions.directConnection && mongoOptions.hosts.length !== 1) {
    throw new MongoParseError('directConnection option requires exactly one host');
  }

  if (
    !mongoOptions.proxyHost &&
    (mongoOptions.proxyPort || mongoOptions.proxyUsername || mongoOptions.proxyPassword)
  ) {
    throw new MongoParseError('Must specify proxyHost if other proxy options are passed');
  }

  if (
    (mongoOptions.proxyUsername && !mongoOptions.proxyPassword) ||

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