LastTransitionTime

LastTransitionTime is a timestamp used in Kubernetes and related API conventions to record when a specific condition last changed its status. It is part of the standard Condition structure that describes an aspect of a resource’s observed state.

A Condition represents a single facet of status and includes fields such as Type, Status, Reason, Message, LastProbeTime, and LastTransitionTime. Status is typically one of True, False, or Unknown, while LastProbeTime notes the most recent observation. LastTransitionTime, by contrast, marks the moment when the Status last transitioned from one value to another.

Semantics and behavior: LastTransitionTime is updated whenever the Condition’s Status changes. If the Status remains the same, LastTransitionTime is not updated. This distinguishes transitions from routine probes. LastProbeTime provides a separate timestamp for the latest check, which may occur without a status change.

Data representation and availability: LastTransitionTime is usually represented as a timestamp in RFC3339 format and serialized via the API as a metav1.Time (often omitempty in JSON/YAML). It may be omitted if no transition has occurred since the resource’s creation or since the field was introduced.

Usage considerations: Clients use LastTransitionTime to assess how long a condition has been in a given state, enabling stability analysis, rollouts, and alerting. It is commonly paired with LastProbeTime to distinguish actual transitions from polling events.

Example: If a Ready condition transitions from False to True at 2023-10-05T12:00:00Z, LastTransitionTime for that condition is set to that timestamp.