Async MQTT client blocks on publish if the client is disconnected and waiting between reconnect attempts

[richturner]

Expected behavior

The async client (in my case Mqtt3AsyncClient) should not block when calling send no matter what the client state is; instead I would expect to get the CompletableFuture<MqttPublish>

Actual behavior

send blocks the calling thread; I guess waiting for the client to be in a connected state?

To Reproduce

1. Create an Mqtt3AsyncClient with reconnect logic, put an invalid host value (so the client can never actually connect)
2. Publish an MQTT message e.g.:

   client.publishWith()
           .topic(message.topic)
           .payload(messageToBytes(message.payload))
           .send()
           .whenComplete((publish, throwable) -> {
               if (throwable != null) {
                   // Failure
                   LOG.log(Level.INFO, "Failed to publish to MQTT broker '" + getClientUri() + "'", throwable);
               } else {
                   // Success
                   LOG.finer("Published message to MQTT broker '" + getClientUri() + "'");
               }
           });

3. Notice that the call blocks on the send call with no Future ever returned

Details

• Affected HiveMQ MQTT Client version(s): 1.2.2
• Used JVM version: Oracle JDK 17.0.1
• Used OS (name and version): Windows 10 64-bit but also same behaviour on Linux Debian AArch64
• Used MQTT version: N/A
• Used MQTT broker (name and version): N/A

[pglombardo]

Hi @richturner - thanks for pointing this issue out. I'll see if I can reproduce this here locally and report back soon.

[pglombardo]

Hi @richturner - I haven't been able to reproduce this. Could you post your client creation code (with reconnect)?

[pglombardo]

Since this issue has gone stale, I'll close it out but if you want to pick up on this again, let us know. We'd be happy to help out!

[Mystery406]

Same problem here, have you found any solutions to this?