Mosquitto publishing retained messages twice upon subscription

[Alexander Rust]

Hi there, 

im currently observing an odd behavior with my Mosquitto broker.

When publishing some retained messages (QOS 0) they are received once by subscribed clients. 

However when I subscribe a new client to the topic after the retained message has been published, Mosquitto delivers the retained message twice for some topics. 

The topics for which this happens are always the same. Clearing the retained topic by publishing an empty retained message and publishing a different payload to the topic shows the same behavior. 

I verified that this is not just a problem with my clients, the following Mosquitto debug output of a client subscription to "#" clearly shows it publishing the same message to the same client twice.

1361525212: Sending PUBLISH to mqtt_737007998021.4031 (d0, q0, r1, m0, '/sys/158293-433MhzBridge/devices/Switch-2', ... (5 bytes))

1361525212: Sending PUBLISH to mqtt_737007998021.4031 (d0, q0, r1, m0, '/tag', ... (3 bytes))

1361525212: Sending PUBLISH to mqtt_737007998021.4031 (d0, q0, r1, m0, '/tag', ... (3 bytes))

1361525212: Sending PUBLISH to mqtt_737007998021.4031 (d0, q0, r1, m0, '/sys/158293-433MhzBridge/devices/Switch-3', ... (5 bytes))

I understand that QOS 0 does not guarantee that the message is delivered exactly once, but it feels like an odd and unnecessary behavior. 

Does anyone know why this happens or has experienced something similar? 

[Roger Light]

Hi Alexander,

This would probably be better discussed on the mosquitto list, but
that aside I think you're seeing the same bug as described here:
https://bugs.launchpad.net/mosquitto/+bug/1116233 I agree, it is odd
and unnecessary and will be fixed in due course.

Cheers,

Roger

[Alexander Rust]

Hi Roger, 

thanks, I had not found that report yet. 

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Mit freundlichen Grüßen / With kind regards
Alexander Rust