max_in_flight option

[Nowogrodzki]

Hello VerneMQ Team!

I have a question regarding the max_in_flight option.
When I specified max_in_flight=100 is it means that 100 messages will be sent to each topic/subscription or is it 100 messages for an entire client

[ioolkos]

@Nowogrodzki max_inflight_messages is applied per client session, at the publishing end of the broker. That is: between the broker and 1 MQTT client. This is not related to topics.

Note that this also only applies to protocol version before 5. For similar behaviour with MQTT v5, look into receive_max_client/receive_max_broker

[ioolkos]

@Nowogrodzki as stated, max_inflight_messages will not apply to v5. Whether you have v3 clients or not, I cannot know. The default will be 20 anyway, whether you configure it or not.

To understand Receive Max for v5: https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html#_Toc3901049

Verne settings:
receive_max_client: MQTT clients are free to choose their own ReceiveMax, but Verne will apply receive_max_client as an upper limit.
receive_max_broker: if the Client can state that it cannot do more than ReceiveMax, then the broker can too. receive_max_broker is to configure the broker to say "I cannot do more than X messages unacklowledged". If a Client comes in with a higher value, Verne will state its own value in the CONNACK answer but then disconnect the client.

Yeah, I'd probably configure at least receive_max_client to something a little lower than 65k.

[Nowogrodzki]

@ioolkos Thank you very much for that information :) I have one more question, but this time regarding shared subscriptions, In the 1.12.4 version new policy has been added, namely prefre_online_before_local, but I saw in the one discussion that you wrote about a policy named prefer_online_to_local, is that the same policy but in the debate or changelog there was a naming issue?

[ioolkos]

@Nowogrodzki if the inflight question is answered, can you mark it answered?
I do not understand the question about shared subscriptions. Yes, typos are possible.

[Nowogrodzki]

Marked :) Regarding shared subscription policies, which name is correct prefer_online_before_local or prefer_online_to_local
In the changelog under the 1.12.4 version new policy is named prefer_online_before_local, In this discussion here you wrote about prefer_online_to_local, I'm a little bit confused about which one is correct

[ioolkos]

ah, sorry, yes it's prefer_online_before_local.