quarkusio/quarkus · error · RuntimeException

mongo config is missing for creating mongo client.

Error message

mongo config is missing for creating mongo client.

What it means

createMongoConfiguration is a private internal helper that must always receive a MongoClientConfig from the mongoConfig.clients() map; this RuntimeException is a defensive assertion that fires only if the config lookup returned null despite a client being requested.

Source

Thrown at extensions/mongodb-client/runtime/src/main/java/io/quarkus/mongodb/runtime/MongoClients.java:320

    private static class ServerSettingsBuilder implements Block<ServerSettings.Builder> {
        public ServerSettingsBuilder(MongoClientConfig config) {
            this.config = config;
        }

        private final MongoClientConfig config;

        @Override
        public void apply(ServerSettings.Builder builder) {
            if (config.heartbeatFrequency().isPresent()) {
                builder.heartbeatFrequency((int) config.heartbeatFrequency().get().toMillis(), TimeUnit.MILLISECONDS);
            }
        }
    }

    private MongoClientSettings createMongoConfiguration(final MongoClientConfig config, final String name,
            final boolean isReactive) {
        if (config == null) {
            throw new RuntimeException("mongo config is missing for creating mongo client.");
        }
        CodecRegistry defaultCodecRegistry = MongoClientSettings.getDefaultCodecRegistry();

        MongoClientSettings.Builder settings = MongoClientSettings.builder();

        if (isReactive) {
            switch (config.reactiveTransport()) {
                case NETTY:
                    // we supports just NIO for now
                    if (!vertx.isNativeTransportEnabled()) {
                        configureNettyTransport(settings);
                    }
                    break;
                case MONGO:
                    // no-op since this is the default behaviour
                    break;
            }
            reactiveContextProviders.stream().findAny().ifPresent(settings::contextProvider);

View on GitHub (pinned to e1c734241f)

Solutions

1. Set `quarkus.mongodb.connection-string` (default client) or `quarkus.mongodb.<name>.connection-string` (named client)
2. Check that the client name passed to the lookup matches the configured prefix exactly
3. Ensure MongoConfigLocation/mongo configuration is loaded before the client is created (don't build clients during early startup phases without config)

Example fix

// before: missing config
// (no quarkus.mongodb.* properties)
// after
quarkus.mongodb.connection-string=mongodb://localhost:27017

// Ensure required Mongo config is present before startup
if (!ConfigProvider.getConfig().getPropertyNames().stream()
        .anyMatch(p -> p.startsWith("quarkus.mongodb"))) {
    throw new ConfigurationException("No quarkus.mongodb.* configuration found");
}

When it happens

Trigger: An internal path resolves a client name that is absent from `quarkus.mongodb.clients` (e.g. extension code requesting a default client when no quarkus.mongodb.* properties exist, or a name mismatch between injector and config).

Common situations: No MongoDB connection URL configured at all while code still triggers client creation; a named client referenced but its `quarkus.mongodb.<name>.connection-string` missing; custom extension code calling MongoClients with a stale client name.

Related errors

• Mongo client named '%s' not found
• The database was not configured for the default Mongo Client
• Failed to load application configuration
• Failed to initialize application configuration
• Unrecognized option for quarkus.bootstrap.misaligned-platfor

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/00e8ae4357e622d7. Report an issue: GitHub.