emqx/MQTTX

[Help] Topics Restored by Clean Session

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#549 opened on Apr 20, 2021

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Description

Can Topics subscribed in the last session got restored in a new session?

Hi there, I am wondering if topics subscribed in the last session can be restored in a new session? The two sessions will use the same clientID to connect to the broker. And these two sessions get their clean-session set to be 0.

From what I have tested, I found there is no way to restore a topic like that. I did the following:

First, I created a new connection, namely connection 1. In this connection, I used clientID client1 to connect to the broker. Then, I subscribed to a topic, namely topic1. Next, I disconnected connection 1 before creating another connection named connection 2. In connection 2, I used the same clientID client1 as before. But I saw no topic1show up in the subscription list.

Would you mind dig into this? Is there something I did wrong, or we do not currently support this feature? The broker I chose is EMQX and nanoMQ (currently underdeveloping).

Thank you.

Contributor guide

Research direction
Investigate MQTTX's subscription management: check if it stores subscriptions locally or relies on the broker's session. Review MQTTX source code for subscription handling and the clean session flag behaviour.
Tech stack
typescript
Domain
backenddesktop
Issue type
Research
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
1
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Under 1 hour
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GitMQTT protocol basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70