quarkus: Healthcheck not working with MongoDB (Panache)

@loicmathieu maybe we can provide some config option to force eager initialization?

Addendum for the answer by @pschmidt88: It’s sufficient to simply call mongoClient.getDatabase(databaseName) to initialize the mongoClient and with it the health check that properly determines whether the provided credentials (static or dynamic via Vault) are valid. You don’t need to actually run a Mongo command. That’s what the Quarkus MongoHealthCheck does.

This should work

@Startup
@ApplicationScoped
class AppLifecycleBean(
    val mongoClient: MongoClient,
) {
  
    fun pingDatabase(@Observes event: StartupEvent) {
        val databaseName = ConfigProvider.getConfig()
            .getValue("quarkus.mongodb.database", String::class.java)

        mongoClient.getDatabase(databaseName).runCommand(Document("ping", 1))
    }
}

Not directly related but I’m also looking for a way to initialize MongoDB connection pool at start. Lazy initialization mentioned here causes application to serve first requests slow. Doing all sort of things for fast serverless boot time but this hits. Will probably fire some basic query in my custom application health check.

@pschmidt88 unfortunatly, this is by design.

We instantiate MongoDB client lazilly, so when the rediness check is done but no use of the MongoDB client has been done yet, the readiness check will not find any MongoDB client instances inside our CDI container and respond OK.

The MongoDB health check is a readiness check so it’s compatible with the usage of a readiness check (if it was a liveness check, checks should have been done eagerly).

Maybe you can force the intitialization of the MongoDB client using a method listening to the StartupEvent and doing a manyal ping using the MongoDB client, this should do the trick. See https://quarkus.io/guides/lifecycle#listening-for-startup-and-shutdown-events