MQTT plugin: option to disable unix timestamps on values.

[3ricj]

• Version of collectd: 5.12.0
• Operating system / distribution: OpenWRT
• Kernel version (if applicable): N/a

Expected behavior

The MQTT plugin would report data up to the server in friendly way for reduced traffic/storage and easier parsing by industry standard MQTT subscribers. For example:

collectd/bob/memory/memory-wired 1714962432
collectd/bob/memory/memory-active 9526575104

Actual behavior

The MQTT Plugin sends data with a unix timestamp on EVERY value - for complex installs this results in massive overhead, plus most MQTT installs don't use this information and drop it on the floor. In fact, most installs use the time of arrive for most reporting and charting. Additionally, most MQTT tools (eg: MQTT Explorer) are unable to parse this format preventing things like charts from being displayed. I understand this is a common method which collectd uses, but the MQTT world doesn't.

collectd/bob/memory/memory-wired 1448840558.555:1714962432
collectd/bob/memory/memory-active 1448840558.555:9526575104

I would like to propose an option which could be placed in the collectd.conf file which would disable all of these unix timestamps on every value.

Steps to reproduce

• Setup any MQTT plugin and observe the output.

[3ricj]

Additionally: There seems to be an an errant \n at the end of the timestamp value pair. This should also be removed.