Rolling upgrades
Upgrade the brain first. Upgrade the agents when you are ready.
A fleet does not upgrade all at once, so z4j supports running one minor version of skew between the brain and its agents. The brain leads and agents follow, which means you can upgrade the control plane, watch it, and roll the agents afterwards on your own schedule instead of during a maintenance window. The wire protocol carries the agent version on every connection, so a pairing outside the supported window is reported with the remedy rather than failing in a way you have to reverse-engineer.
Ships with
- The brain may run one minor version ahead of its agents
- Upgrade the control plane and the fleet independently
- Agent version travels on the connection, so skew is visible rather than inferred
- A pairing outside the window is reported with what to do about it
- Coordinated package floors stop a current adapter installing beside an incompatible dispatcher
Highlights
- Mixed-version fleets are a tested configuration, exercised in both directions against a real prior release
- Retry authority is bound to the worker generation that executes it, so an old worker cannot be handed new work
Related