First, can we get your full configuration? The config you left in the 3rd comment is only the agent settings. It would be good to see what other configuration settings you are using, especially for the inputs and ouptus.
Second, what type of system is hosting these systems? Is this a raspberry pi? laptop? How much memory and CPU does it have?
You have shown one error and one warning from Telegraf. First the error from the
2021-12-20T08:18:45Z E! [inputs.mqtt_consumer] Error in plugin: connection lost: pingresp not received, disconnecting
This is reporting that the MQTT client Telegraf uses did not get a response from your MQTT server in the allowed time. If you continue reading the logs, you will see that the MQTT server disconnects and then Telegraf immediately tries to reconnect once again.
I am assuming you are hosting both the MQTT server, Telegraf, and InfluxDB all on the same system given the container status screenshot. Given your container load for the emqx-2.0, there is probably contention on your system for accessing resources. As a result, these disconnections and reconnects will continue to happen with such a heavily loaded system.
The warning you showed was from
did not complete within its flush interval
Assuming the flush interval is what the agent config shows,
10s, this means that the write to InfluxDB took longer than 10 seconds. Looking at your short log, I see some writes taking many seconds. Similar to the above issue with the MQTT server, this is again probably load-related if all three services are hosted on the same system.
Hope that helps!