TechnitiumSoftware/DnsServer · error · InvalidOperationException

MaxMind database not initialized.

Error message

MaxMind database not initialized.

What it means

Thrown by GeoDistanceApp CNAME.ProcessRequestAsync when _maxMind is null. CNAME counterpart of error 32: without a MaxMind reader the distance calculation cannot run and the lookup raises InvalidOperationException.

Source

Thrown at Apps/GeoDistanceApp/CNAME.cs:99

        #region public

        public Task InitializeAsync(IDnsServer dnsServer, string? config)
        {
            _dnsServer = dnsServer;
            _maxMind = MaxMind.Create(dnsServer);

            return Task.CompletedTask;
        }

        public Task<DnsDatagram?> ProcessRequestAsync(DnsDatagram request, IPEndPoint remoteEP, DnsTransportProtocol protocol, bool isRecursionAllowed, string zoneName, string appRecordName, uint appRecordTtl, string appRecordData)
        {
            DnsQuestionRecord question = request.Question[0];

            if (!question.Name.Equals(appRecordName, StringComparison.OrdinalIgnoreCase) && !appRecordName.StartsWith('*'))
                return Task.FromResult<DnsDatagram?>(null);

            if (_maxMind is null)
                throw new InvalidOperationException("MaxMind database not initialized.");

            Location? location = null;

            byte scopePrefixLength = 0;
            EDnsClientSubnetOptionData requestECS = request.GetEDnsClientSubnetOption();
            if (requestECS is not null)
            {
                if ((_maxMind.IspReader is not null) && _maxMind.IspReader.TryIsp(requestECS.Address, out IspResponse? csIsp) && (csIsp.Network is not null))
                    scopePrefixLength = (byte)csIsp.Network.PrefixLength;
                else if ((_maxMind.AsnReader is not null) && _maxMind.AsnReader.TryAsn(requestECS.Address, out AsnResponse? csAsn) && (csAsn.Network is not null))
                    scopePrefixLength = (byte)csAsn.Network.PrefixLength;
                else
                    scopePrefixLength = requestECS.SourcePrefixLength;

                if (_maxMind.CityReader.TryCity(requestECS.Address, out CityResponse? csResponse) && csResponse.Location.HasCoordinates)
                    location = csResponse.Location;
            }

View on GitHub (pinned to d0484b6c1e)

Solutions

1. Place GeoLite2-City.mmdb (or GeoIP2-City.mmdb) in the ApplicationFolder.
2. Restart the service so the MaxMind constructor initialises _maxMind.
3. Verify error 34 does not reappear at startup.

if (_maxMind is null)
    _log.Warn("GeoDistanceApp CNAME query for {0} skipped: MaxMind City database not loaded.", appRecordName);

try { return await ProcessDistanceCnameAsync(request, ...); }
catch (InvalidOperationException ex) when (ex.Message.Contains("MaxMind database not initialized"))
{ _log.Error("GeoIP City database missing — deploy GeoLite2-City.mmdb."); return Task.FromResult<DnsDatagram?>(null); }

When it happens

Trigger: A CNAME query matches a GeoDistanceApp record while _maxMind is null, i.e. the City database file was missing at startup.

Common situations: City database not deployed or removed; CNAME distance records then fail.

Related errors

• MaxMind database not initialized.
• MaxMind database not initialized.
• MaxMind database not initialized.
• MaxMind database not initialized.
• MaxMind database not initialized.

AI-assisted analysis of TechnitiumSoftware/DnsServer@d0484b6c1e (2026-08-13). Data as JSON: /api/errors/a4c840ba0066d6c3. Report an issue: GitHub.