COS 2 release notes

October 2025

These release notes cover new features and changes in COS 2.

COS 2 is designated as a short-term support release. This means it will continue to receive security updates and critical bug fixes for 9 months.

See our release policy and upgrade instructions.

Requirements and compatibility

See system requirements.

COS 2 is compatible with Juju v3.6+. When deployed using terraform, Juju v3.6.11+ is recommended.

What’s new in COS 2

  • Terraform modules for COS and COS Lite. As Juju bundles are deprecated, the standard way of deploying COS is now using the Juju Terraform provider.

  • Grafana v12. We upgraded the workload version from Grafana 9 to Grafana 12. A thorough review of Grafana’s breaking changes and how they affect us is available on Discourse.

  • Opentelemetry collector. Charmed opentelemetry-collector was released. The charm was designed to be a drop-in replacement for the grafana-agent charm (upstream grafana-agent is EOL since November 2025, and we will support charmed grafana-agent until July 2026).

  • extra_alert_labels config option. A new config option in grafana-agent and opentelemetry-collector enabled adding custom labels to alert rules. Custom labels are useful for differentiating alerts coming from sites with different SLAs.

  • API links in catalogue-k8s. The cards in catalogue-k8s now support extra links for documentation and APIs. COS charms now provide links to the workload API, making it easier to locate ingress URLs for workloads without a web UI.

  • Opentelemetry collector. Charmed opentelemetry-collector’s workload is pinned to version 0.130 because the upstream opentelemetry-collector-contrib project 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-collector charms rely on lokiexporter to 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 (logging endpoint). Support will then be fully dropped in 27.04, and the opentelemetry-collector charms will no longer be pinned to v0.130.

Notable changes in peripheral charms

  • Multiple scripts in script-exporter. The script exporter VM charm can now take an archive of scripts. It can now be deployed on 20.04, 22.04 and 24.04.

  • Prior to cos-proxy rev166, duplicate telemetry exists after upgrade and config-changed hooks. Follow these remediation steps to resolve, requiring you to upgrade cos-proxy to >=rev166 via track2. This also includes the feature of scrape-configs and alert rules for cos-agent relations.

Backwards-incompatible changes

  • Charms from track 2 can be deployed on juju models v3.6+.

  • Terraform module variable model_name renamed to model in all charms.

  • Grafana v12 changes how the panel view URL is generated for repeated panels. Links to repeated panels in a dashboard changed slightly; previously bookmarked links to a repeated panel (not its dashboard) will no longer work.

Deprecated features

  • The LogProxyConsumer charm library (owned by Loki) is deprecated. Use Pebble log forwarding instead.