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john30 / ebusd

daemon for communication with eBUS heating systems
GNU General Public License v3.0
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Duplicate messages when polling values over mqtt #170

Closed jjakob closed 5 years ago

jjakob commented 6 years ago

When polling for values using mqtt /get topic, for example:

mosquitto_pub -q 1 -n -t ebusd/sc/Coll1Sensor/get

And monitoring response using mosquitto_sub, sometimes a duplicate message with identical contents is received within 1-5 seconds of the initial response. Tested with publish & subscribe QoS both at 1 (the published /get messages don't get duplicated, the received value messages do). My initial hunch was on the QoS ebusd uses to publish messages (if it's 0) but I can't see a way to change it or what its default is.

The use-case is ebusd -> mosquitto -> telegraf -> InfluxDB, so any duplicate messages will use up valuable space. The polling is via a custom Go script that publishes the /get topics over mqtt.

john30 commented 6 years ago

did you define that message as to be polled? or did you use the HTTP port or the TCP port to life the message to being polled?

andig commented 6 years ago

I think I've seen something that feels similar in https://github.com/john30/ebusd/issues/156:

the ebusd instance that initiates the bus read seems to receive about double the number of messages (two per forced read instead of one)

its visible in the ebusd logfile, too.

jjakob commented 6 years ago

No, the configuration doesn't define it as polled:

ebusd-2.1.x/en/vaillant/ec.solsy.sc.csv:r,,Coll1Sensor,Collector1Sensor,,,,"0900",,,tempsensor,,,Temperature of COL1 sensor

So if I can somehow override this to be polled, I wouldn't need to use /get to poll the values. Is there a way to do this without external tools (like a custom config)?

john30 commented 6 years ago

during runtime, you can easily use "read -p ..." to set a message to being polled. If you want to change it permanently, you'd have to adjust the corresponding CSV entry though.

jjakob commented 6 years ago

Thanks, I adjusted the CSV and now the messages are updated on mqtt without having to poll them via /get, so I'm not getting duplicates any more. However the original bug of duplicated messages when polling over /get is probably still unfixed. I'm using ebusd-3.1_amd64-stretch_mqtt1.deb. Also when polling using /get, every poll request gets a message response even if the value is unchanged, is this the intended behaviour?

john30 commented 6 years ago

yes, this is the desired behaviour since for an explicit /get or /set request is also supposed to produce an answer.