connect() blocks forever if reconnect configured and broker cannot be reached

[dowhiletrue]

Expected behavior

Connecting a client with reconnect configured should throw if it can't connect initially.

Actual behavior

It blocks infinitely

To Reproduce

Reproducer code

Mqtt5Client.builder().serverHost("hostWithoutRunningBroker").automaticReconnectWithDefaultConfig().toBlocking().connect(...)

Details

• Affected HiveMQ MQTT Client version(s): 1.1.0
• Used JVM version: 11

[SgtSilvio]

This was actually intended.
We should discuss what the default behavior should be.
You can work around in the mean time:

Mqtt5Client.builder()
        ...
        .automaticReconnectWithDefaultConfig()
        .addDisconnectedListener(context -> {
            if (context.getClientConfig().getState() == MqttClientState.CONNECTING) {
                context.getReconnector().reconnect(false);
            }
        })
        ...

[dowhiletrue]

Thanks for the workaround!

There are three options on top of my mind:

• block
• throw
• continue and try to connect later

Which option fits best depends on the use-case. Make the behavior configurable?

[Razikus]

Hello i just want to poke this, cause it tooks me 2 days to understand why "exceptionally" is not working

This definitely needs to be highlighted somewhere

[ravenblackdusk]

I think I might have encountered this problem. @dowhiletrue I think throwing an exception should be the default behavior as it informs the developers if their connection configuration is incorrect; I think jdbc connection pools also have such default behavior. @SgtSilvio can you please explain what happens if I use your workaround? does it attempt to reconnect automatically initially or otherwise or does it abandon reconnection and throw an exception?

[CJure]

@SgtSilvio
I also had this problem: https://stackoverflow.com/questions/71467511/hivemq-mqtt-client?noredirect=1#comment126319388_71467511

Is it not possible to have automaticReconnectWithDefaultConfig() and that

.whenComplete((connAck, throwable) ->

throws error?

[pglombardo]

Since this issue has gone stale, I've filed a feature request with summary (and current work-around) in #622. If anyone has other ideas for improvement, please add to #622.

Thanks all for pointing this out and the helpful feedback!