# How to properly shutdown when asyncClient.connect() fails?

**URL:** <https://community.hivemq.com/t/how-to-properly-shutdown-when-asyncclient-connect-fails/2541>\
**Category:** HiveMQ Client Library\
**Created:** [December 6, 2023, 5:56pm UTC](https://community.hivemq.com/t/how-to-properly-shutdown-when-asyncclient-connect-fails/2541 "2023-12-06T17:56:57Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![MartinHH](https://avatars.discourse-cdn.com/v4/letter/m/53a042/32.png) [@MartinHH](https://community.hivemq.com/u/MartinHH)\
**Post date:** [December 6, 2023, 5:56pm UTC](https://community.hivemq.com/t/how-to-properly-shutdown-when-asyncclient-connect-fails/2541/1 "2023-12-06T17:56:57Z")

</div>

Hi there, I’m looking for help with the async client:

Consider this minimal example (very similar to the [AsyncSubscriber example from the official blog](https://www.hivemq.com/article/mqtt-client-api/the-hivemq-mqtt-client-library-for-java-and-its-async-api-flavor/)):

```auto
import com.hivemq.client.mqtt.MqttGlobalPublishFilter;
import com.hivemq.client.mqtt.mqtt5.Mqtt5Client;

import static java.nio.charset.StandardCharsets.UTF_8;

public class AsyncSubscriber {

    public static void main(final String [] args) {
        final var asyncClient = Mqtt5Client.builder()
                .identifier("async-subscriber")
                .serverHost("localhost")
                .serverPort(1883)
                .buildAsync();

        asyncClient.publishes(MqttGlobalPublishFilter.ALL, publish -> {
            System.out.println("Received: " + new String(publish.getPayloadAsBytes(), UTF_8));
        });

        asyncClient.connect()
                .thenCompose(connAck -> {
                    System.out.println("Successfully connected!");
                    return asyncClient.disconnect();
                }).thenRun(() -> {
                    System.out.println("Successfully disconnected!");
                }).exceptionally(throwable -> {
                    System.out.println("Something went wrong: " + throwable.getMessage());
                    return null;
                });
    }
}

```

When I run this while a broker is available under localhost:1883, it prints “Successfully disconnected!\nSuccessfully disconnected!” and then exits.

When I run this while no broker is available under localhost:1883, it prints "“Something went wrong: …” with a `ConnectionFailedException` and then **will not exit**.

I noticed that it will exit on failed connection if I do not `asyncClient.publishes()` so maybe that starts some threads that won’t get shutdown?

Anyway: my main question is: **how do I properly shutdown the client and all of its resources when `connect()` fails**?

---

<div class="post-metadata">

**Author:** ![Daria\_H](https://avatars.discourse-cdn.com/v4/letter/d/dfb087/32.png) [@Daria\_H](https://community.hivemq.com/u/Daria_H)\
**Post date:** [December 7, 2023, 9:59am UTC](https://community.hivemq.com/t/how-to-properly-shutdown-when-asyncclient-connect-fails/2541/2 "2023-12-07T09:59:53Z")

</div>

```auto
asyncClient.connect()
                .thenCompose(connAck -> {
                    System.out.println("Successfully connected!");
                    return asyncClient.disconnect();
                }).thenRun(() -> {
                    System.out.println("Successfully disconnected!");
                }).exceptionally(throwable -> {
                    System.out.println("Something went wrong: " + throwable.getMessage());
                    System.exit(1);
                    return null;
                });

```

---

<div class="post-metadata">

**Author:** ![MartinHH](https://avatars.discourse-cdn.com/v4/letter/m/53a042/32.png) [@MartinHH](https://community.hivemq.com/u/MartinHH)\
**Post date:** [December 8, 2023, 6:30pm UTC](https://community.hivemq.com/t/how-to-properly-shutdown-when-asyncclient-connect-fails/2541/3 "2023-12-08T18:30:09Z")

</div>

Thanks for the reply!

However: I am looking for a way how I can shutdown the client and all of the ressources that it aquired without actually terminating the whole application.

My example code tries to shutdown the whole application, but that was just meant to provide a minimal example of what I tried so far (proving threads started by the asyncClient would be left running in the background).

---

<div class="post-metadata">

**Author:** ![MartinHH](https://avatars.discourse-cdn.com/v4/letter/m/53a042/32.png) [@MartinHH](https://community.hivemq.com/u/MartinHH)\
**Post date:** [December 9, 2023, 9:07am UTC](https://community.hivemq.com/t/how-to-properly-shutdown-when-asyncclient-connect-fails/2541/4 "2023-12-09T09:07:22Z")

</div>

I found a workaround that is acceptable for me:

If I register my publishes callback via the Rx API and then keep the returned `Disposable` and call `dispose()` on it after both a successful disconnect and a failure to connect, then everything appears to be disposed properly:

```auto
package org.example;

import com.hivemq.client.mqtt.MqttGlobalPublishFilter;
import com.hivemq.client.mqtt.mqtt5.Mqtt5Client;

import static java.nio.charset.StandardCharsets.UTF_8;

public class AsyncSubscriber {

    public static void main(final String[] args) {
        final var asyncClient = Mqtt5Client.builder()
                .identifier("async-subscriber")
                .serverHost("localhost")
                .serverPort(1883)
                .buildAsync();

        final var disposable = asyncClient
                .toRx()
                .publishes(MqttGlobalPublishFilter.ALL)
                .subscribe(publish -> {
                    System.out.println("Received: " + new String(publish.getPayloadAsBytes(), UTF_8));
                });

        asyncClient.connect()
                .thenCompose(connAck -> {
                    System.out.println("Successfully connected!");
                    return asyncClient.disconnect();
                }).thenRun(() -> {
                    System.out.println("Successfully disconnected!");
                    disposable.dispose();
                }).exceptionally(throwable -> {
                    System.out.println("Something went wrong: " + throwable.getMessage());
                    disposable.dispose();
                    return null;
                });
    }
}

```

(For real-world use-cases, one should probably also take care of handling `onError` of the publishes, but I’m fine with that.)