Hello Tom,
Please find below the general description on how messages are expected to be stored on the Broker when using QoS1:
Queued QoS 1 messages are stored on the broker until either of the following happens:
- The message expires;
- The corresponding session is removed from the broker (Session and Message Expiry Intervals - MQTT 5 Essentials Part 4);
- They are delivered and acknowledged by the client;
MQTT brokers don’t provide any mechanism for logging historical data for later analysis. The only way to see the history of messages published to a topic is to store them somewhere and persist them into a time series database (e.g. InfluxDB) as you are already planning to use.
Best regards,
Diego from HiveMQ Team