Release notes¶
COS 3¶
May 2026
These release notes cover new features and changes in COS 3.
COS 3 newer versions of all underlying charms, as well as new features around charmed opentelemetry-collector.
COS 3 is designated as a long-term support (LTS) release. This means it will continue to receive security updates and critical bug fixes for 15 years.
Note
COS track 3 is a release track for the COS bundle and does not correspond to any individual charm track on Charmhub. The individual charms retain their own versioning.
If you have COS 2 installed, make plans to upgrade to COS 3 before July 2026.
See our release policy and upgrade instructions.
To report bugs or security issues, refer to the index of COS components.
Requirements and compatibility¶
See system requirements.
COS 3 is compatible with Juju v3.6+.
What’s new in COS 3¶
Opentelemetry collector. Charmed opentelemetry-collector’s workload is pinned to version 0.130 because the upstream
opentelemetry-collector-contribproject dropped support for Loki exporter in release v0.131.0, stating that users can migrate to the OTLP exporters instead.The logging integrations for the
opentelemetry-collectorcharms rely onlokiexporterto send logs to Loki push API endpoints. Loki only recently received upstream support for an OTLP endpoint, and migrating to an OTLP-first ecosystem in COS began in 26.04. The objective is to have support for OTLP ecosystem-wide by the end of 26.10 and to deprecate the Loki Push API feature (loggingendpoint). Support will then be fully dropped in 27.04, and theopentelemetry-collectorcharms will no longer be pinned tov0.130.
COS components¶
Component |
Version |
|---|---|
alertmanager |
0.31 |
catalogue |
|
grafana |
12.4 |
loki |
3.7 |
mimir |
2.17 |
opentelemetry-collector |
0.130 |
s3-integrator |
|
self-signed-certificates |
|
tempo |
2.10 |
traefik |
2.11 |
COS Lite components¶
Component |
Version |
|---|---|
alertmanager |
0.31 |
catalogue |
|
grafana |
12.4 |
loki |
3.7 |
prometheus |
3.11 |
traefik |
2.11 |
Notable changes in peripheral charms¶
Promtail is no longer maintained by Grafana Labs¶
LogProxyConsumer is relying on promtail for scraping log lines from files, and sending them to Loki.
Since March 2026, promtail is no longer under active development by Grafana Labs.
Starting COS 3, it is recommended to use pebble for forwarding logs from kubernetes workloads.
You can use the LogForwarder object from the loki_push_api charm library to automatically set up pebble for log forwarding.
Note that for this to work, the workload needs to emit logs to stdout (this is standard practice in kubernetes).
Backwards-incompatible changes¶
If you are using charmed Grafana Agent to push telemetry to COS, note that the vendor announced end-of-life, so we will not be supporting the charm beyond July 2026. Make plans to upgrade to charmed OpenTelemetry Collector.