Available for canary rollouts since v0.10.0
Available for blue-green rollouts since v1.0
One use case is for a Rollout to label or annotate the desired/stable pods with user-defined
labels/annotations, for only the duration which they are the desired or stable set, and for the
labels to be updated/removed as soon as the ReplicaSet switches roles (e.g. from desired to stable).
The use case which this enables, is to allow prometheus, wavefront, datadog queries and dashboards
to be built, which can rely on a consistent labels, rather than the
which is unpredictable and changing from revision to revision.
A Rollout using the canary strategy has the ability to attach ephemeral metadata to the stable or
canary Pods using the
canaryMetadata fields respectively.
spec: strategy: canary: stableMetadata: labels: role: stable canaryMetadata: labels: role: canary
A Rollout using the blue-green strategy has the ability to attach ephemeral metadata to the active
or preview Pods using the
previewMetadata fields respectively.
spec: strategy: blueGreen: activeMetadata: labels: role: active previewMetadata: labels: role: preview
During an update, the Rollout will create the desired ReplicaSet while also merging the metadata
previewMetadata to the desired ReplicaSet's
This results in all Pods of the ReplicaSet being created with the desired metadata. When the rollout
becomes fully promoted, the desired ReplicaSet becomes the stable, and is updated to use the labels
and annotations under
activeMetadata. The Pods of the ReplicaSet will then be
updated in place to use the stable metadata (without recreating the pods).
In order for tooling to take advantage of this feature, they would need to recognize the change in labels and/or annotations that happen after the Pod has already started. Not all tools may detect this.