[collectd] Version 6.0.0.rc0 is available.

[Florian Forster]

Hi all,

TLDR: collectd 6.0.0.rc0 is a pre-release of the new major version.
Our aim is to closely align with OpenTelemetry. Please take it for a
spin and provide feedback.

I'm very happy to announce that collectd 6.0.0.rc0 is available for
download. This is a preview of collectd's next major release, collectd
6.

Being a new major release, collectd 6 makes breaking changes and is
not a drop-in replacement for collectd 5.

The central change is that metrics are identified by a set of labels.
The "DF" plugin is a good demonstration for why this is useful. In
collectd 5, the "type instance" is set to the filesystem state, e.g.
"used" and "free". The plugin instance is either set to the block
device name or the mount point, depending on a configuration option.
By using a label set to identify the metric we can report both, block
device and mount point, as well a additional information, e.g.
filesystem type.

The resource being monitored (physical device, virtual machine, cloud
service, etc.) is also identified by a label set. This allows us to
identify resources where the concept of "hostname" doesn't apply, such
as modbus devices, cloud services, etc.

Overall, the goal is to align closely and integrate with OpenTelemetry
(https://opentelemetry.io/). The CPU, DF, disk, interface, and memory
plugins have been updated to implement the "OpenTelemetry Semantic
Conventions" as closely as possible. The new "Write OpenTelemetry"
plugin writes metrics to an OpenTelemetry "collector" using an
efficient binary protocol. The "Write HTTP" plugin has been extended
to be able to produce OpenTelemetry compatible JSON data. The "Write
Prometheus" plugin has been changed to perform the same mapping of
metrics into the Prometheus namespace.

A large number of plugins work in "compatibility mode" and are
disabled by default. These plugins will get breaking updates in future
collectd 6 releases. You can use the "--enable-compatibility-mode"
configure flag to build these plugins.

This is a pre-release. That means that we're not giving any
compatibility guarantees at this point. Our main goal is to gather
feedback and iterate. The plugins mentioned above are probably quite
stable, unless compatibility issues with the wider OpenTelemetry
ecosystem surface.

Download
https://storage.googleapis.com/collectd-tarballs/collectd-6.0.0.rc0.tar.bz2

Release Notes
https://github.com/collectd/collectd/releases/tag/collectd-6.0.0.rc0

Big thanks to Eero Tamminen and Matthias Runge who have been
instrumental in making this possible, as well as the many
contributors. Thank you!

Best regards,
—octo