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max_inflight_messages=1 broken on Mosquitto-1.6.3 #1332

xmas79 opened this issue Jul 5, 2019 · 2 comments


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commented Jul 5, 2019

it seems that max_inflight_messages=1 is broken on the new mosquitto-1.6.3 broker implementation. A client (tried with mosquitto_pub v1.6.3 and older releases as well) publishing messages with QoS2 to a such configured broker will just stuck waiting for a reply.

As I understand it, the problem seems related to outgoing QoS quota being decremented for the CONNACK packet, leaving the broker without any quota left for answering subsequent requests.

A simple "dialogue" between a broker and a client:

Log from Mosquitto Broker:

1562328636: New connection from on port 1883.
1562328636: New client connected from as mosquitto_pub (p2, c1, k60).
1562328636: No will message specified.
1562328636: Sending CONNACK to mosquitto_pub (0, 0)
1562328636: Received PUBLISH from mosquitto_pub (d0, q2, r0, m1, 'test', ... (5 bytes))
1562328696: Received PINGREQ from mosquitto_pub
1562328696: Sending PINGRESP to mosquitto_pub

Log from mosquitto_pub:

mosquitto_pub -h -t "test" -q 2 -d -m "hello" -i "mosquitto_pub"
Client mosquitto_pub sending CONNECT
Client mosquitto_pub received CONNACK (0)
Client mosquitto_pub sending PUBLISH (d0, q2, r0, m1, 'test', ... (5 bytes))
Client mosquitto_pub sending PINGREQ
Client mosquitto_pub received PINGRESP

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commented Jul 10, 2019

I have the same problem. The issue also exists in version 1.6.2.

ralight added a commit that referenced this issue Jul 30, 2019


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commented Jul 30, 2019

Thanks for the reports both, I believe this is now fixed in the fixes branch.

@ralight ralight added this to the 1.6.4 milestone Jul 30, 2019

@ralight ralight closed this Aug 1, 2019

vankxr added a commit to vankxr/mosquitto that referenced this issue Aug 9, 2019

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