Question. about user properties on automatic reconnect...

[zhangheng1983]

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❓ Question

Hi，I set user properties as key is “client_info” to connect packet，when MQTT client connect, server can accept the connect packet with "client_info" properties.
But, when client reconnect because of network error etc, the "client_info" properties is absent.
Is the user properties cann't be set to reconnect packet?

  1)  In MQTT client code, I bind "client_info" properties as follow:
   final Mqtt5BlockingClient client = Mqtt5Client.builder()
                        .identifier(getClientId())
                        .serverHost(HOST)
                        .serverPort(PORT)
                        .simpleAuth()
                            .username(USERNAME)
                            .password(ByteBuffer.wrap(PASSWORD.getBytes(StandardCharsets.UTF_8)))
                        .applySimpleAuth()
                        .automaticReconnect()
                            .initialDelay(60, TimeUnit.SECONDS)
                            .maxDelay(60, TimeUnit.SECONDS)
                        .applyAutomaticReconnect()
                        .buildBlocking();
   final Mqtt5ConnectBuilder connectBuilder = Mqtt5Connect.builder()
                        .cleanStart(true)
                        // "client_info" properties
                        .userProperties().add("client_info", getClientInfo()).applyUserProperties()
                        .keepAlive(connectKeepAliveInSeconds());

    // That's ok, server can accept the first connect packet with "client_info" properties
    client.connect(connectBuilder.build());
    ......

    2)  In MQTT extensions, I handle the "client_info" properties as follows:
    Services.securityRegistry().setAuthenticatorProvider(input -> new ClientAuthenticator());
    ......
    public class ClientAuthenticator implements SimpleAuthenticator {
        @Override
         public void onConnect(final @NotNull SimpleAuthInput input, final @NotNull SimpleAuthOutput output) {
             // I cann't get "client_info" properties on reconnect
             final List<String> list = input.getConnectPacket().getUserProperties().getAllForName("client_info");
         }
    }

How can I set "client_info" properties on connect package and reconnect packet?

Is it possible to notify "client_info" through publish message?

📎 Additional context

[pglombardo]

Hi @zhangheng1983 - the reasoning for this is also explained here.

To set user properties on reconnect, you can add a addDisconnectedListener and configure the reconnector similar to here. With that you can then call:

connectWith().userProperties.add("client_info", getClientInfo()).applyUserProperties()

[pglombardo]

Hi @zhangheng1983 - have you made any progress on this issue?

[dr0-dev]

what if the reconnection is handled by the automaticReconnect() from the original client? would I need to handle the reconnection manually ?

[zhangheng1983]

Hi @zhangheng1983 - have you made any progress on this issue?

Thanks for your reply. My test result as follows:

1. I add DisconnectedListener and ConnectedListener
   ......
   final Mqtt5BlockingClient client = Mqtt5Client.builder()
   ......
   .automaticReconnectWithDefaultConfig()
   .addDisconnectedListener(MainActivity.this)
   .addConnectedListener(MainActivity.this)
   .buildBlocking();
   ......
   @OverRide
   public void onDisconnected(@nonnull MqttClientDisconnectedContext context) {
   LOG.i(TAG, "on disconnected ...");
   final Mqtt5ClientDisconnectedContext context5 = (Mqtt5ClientDisconnectedContext) context;
   context5.getReconnector()
   .reconnectWhen(getOAuthToken(), (token, throwable) -> { // first reconnect would be delayed 2s but OAuth server needs more time
   context5.getReconnector().connectWith().userProperties().add("client_info", getClientInfo()).applyUserProperties();
   LOG.i(TAG, "set 'client_info' to reconnector ...");
   });
   }

   private static CompletableFuture<byte[]> getOAuthToken() {
   return CompletableFuture.supplyAsync(() -> {
   return new byte[] {1, 2, 3};
   });
   }

   @OverRide
   public void onConnected(MqttClientConnectedContext context) {
   LOG.i(TAG, "on connected ...");
   }

2. I start MQTT client connection, my MQTT broker do received the connection with "client_info"

3. I CLOSE MY WIFI on device, yes it print "on disconnected ..." and "set 'client_info' to reconnector ..."

4. I OPEN MY WIFI, it print "on connected ..."

5. When reconnected, my MQTT broker have still not received 'client_info' user properties.

[zhangheng1983]

Now I handle this issue as follows:

1. Close MQTT client auto reconnect
2. Add a watch process to check MQTT client status, if it disconect, close it and recreate new MQTT client with 'client_info'
   Resolve the issue, Maybe it consume more resources.

[zhangheng1983]

what if the reconnection is handled by the automaticReconnect() from the original client? would I need to handle the reconnection manually ?

I think. If you configure automaticReconnect, you not need handle reconnection. Otherwise, you can handle reconnect in DisconnectedListener, or check the client status in additional thread.