Ambiguous services found

Hello,

I’m trying to run the example here but I receive the following error and I have no idea what I’m doing wrong or it’s a bug in the framework itself?

Exception in thread "main" java.lang.IllegalArgumentException: Ambiguous services found for class com.zaxxer.hikari.HikariDataSource : [interface java.io.Closeable, interface javax.sql.DataSource]. Use register() methods to specify service.
	at io.activej.service.ServiceGraphModule.doLookupAdapter(ServiceGraphModule.java:600)
	at io.activej.service.ServiceGraphModule.lookupAdapter(ServiceGraphModule.java:570)
	at io.activej.service.ServiceGraphModule.getServiceOrNull(ServiceGraphModule.java:542)
	at io.activej.service.ServiceGraphModule.getCombinedServiceOrNull(ServiceGraphModule.java:474)
	at io.activej.service.ServiceGraphModule.doStart(ServiceGraphModule.java:428)
	at io.activej.service.ServiceGraphModule.doStart(ServiceGraphModule.java:401)
	at io.activej.service.ServiceGraphModule.lambda$serviceGraph$3(ServiceGraphModule.java:283)
	at io.activej.service.ServiceGraph.startFuture(ServiceGraph.java:278)
	at io.activej.service.ServiceGraphModule$1.start(ServiceGraphModule.java:296)
	at io.activej.launcher.Launcher.startServices(Launcher.java:235)
	at io.activej.launcher.Launcher.launch(Launcher.java:158)
	at ship.cars.dataone.WebApp.main(WebApp.java:73)

My snippet

import com.zaxxer.hikari.HikariDataSource;
import io.activej.config.Config;
import io.activej.http.AsyncServlet;
import io.activej.http.HttpResponse;
import io.activej.inject.annotation.Inject;
import io.activej.inject.annotation.Provides;
import io.activej.inject.module.AbstractModule;
import io.activej.inject.module.Module;
import io.activej.inject.module.Modules;
import io.activej.launcher.Launcher;
import io.activej.launchers.http.MultithreadedHttpServerLauncher;
import io.activej.promise.Promise;
import io.activej.service.ServiceGraphModule;
import ship.cars.dataone.utils.HikariConfigConverter;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;


public class WebApp extends MultithreadedHttpServerLauncher {
    @Inject
    DataSource dataSource;

    @Override
    protected void run() {
        try (Connection connection = dataSource.getConnection();
             Statement statement = connection.createStatement()
        ) {
            statement.executeUpdate("SELECT NOW();");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @Override
    protected void onStart() {
        System.out.println("TABLES BEFORE:");
    }

    @Override
    protected Module getOverrideModule() {
        return Modules.combine(
                ServiceGraphModule.create(),
                // db module
                new AbstractModule() {
                    @Provides
                    DataSource dataSource(Config config) {
                        HikariConfigConverter converter = HikariConfigConverter.create().withAllowMultiQueries();
                        return new HikariDataSource(config.get(converter, "hikari"));
                    }
                }
        );
    }

    @Provides
    AsyncServlet servlet() {
        return request -> Promise.of(
                HttpResponse.ok200()
                    .withPlainText("Hello, World!"));
    }

    public static void main(String[] args) throws Exception {
        Launcher launcher = new WebApp();
        launcher.launch(args);
    }
}

Thank you in advance 😃

[eduard-vasinskyi]

Hi, @vencivenc

Thank you for providing a snippet, this has greatly helped in pinpointing a problem.

Since MultithreadedHttpServerLauncher uses a ServiceGraphModule, all of the provided services are started/stopped by the ServiceGraph. A ServicGraphModule contains pre-registered ServiceAdapters that describe how a start/stop operation should be performed for a certain class.

A HikariDataSource implements both DataSource and Closeable interfaces. Service graph cannot choose whether it should start/stop a HikariDataSource as a DataSource or as a Closeable. You need to manually define a service adapter for HikariDataSource as a combination of Closeable and DataSource service adapters.

You can modify your snippet by replacing the ServiceGraphModule.create() line with:

ServiceGraphModule.create()
       .register(HikariDataSource.class, ServiceAdapters.combinedAdapter(
               ServiceAdapters.forCloseable(),
               ServiceAdapters.forDataSource()))

BTW, you should probably replace statement.executeUpdate("SELECT NOW();") with statement.executeQuery("SELECT NOW();")

[eduard-vasinskyi]

ActiveJ Redis client works on top of ActiveJ AsyncTcpSocket, so it is ideal for our eventloop-based threading model. All the I/O is handled directly by the eventloop, so you do not need to use an external executor which would add the overhead of a thread context switching, etc.

As for using a connection pool, on second thought, I believe that your implementation of a single connection reuse is optimal for our threading model. A Redis server is single-threaded, so having multiple connections would not increase performance. All you need is a single connection per thread (worker). Your initial implementation from https://github.com/activej/activej/issues/149#issuecomment-1025743379 seems to be the correct one (although, you might need to add a reconnection handling routine).

I do not know why you got a performance drop when reusing a single connection. I did some testing/benchmarking and I got quite opposite results. The performance of a single connection is well above the performance of a new connection per request. On my machine, I benchmarked ~2 million requests per second using a single thread / single connection.