Rolling Upgrades

No software is perfect and few are ever complete. Updates are, or should be, part of the day to day operations. This document describes the steps you can follow to upgrade Replicante Core without service interruption.

This document does NOT describe how to update Replicante Core dependencies.
You should take care to keep them up to date as well.

The upgrade path relies on Replicante Core high availability features to avoid loss of service. Nodes are updated one at a time, upgrading them between compatible versions. Once all nodes are up to date and restarted the upgrade is complete.

1. Read the upgrade notes for any special consideration for the version you are upgrading to.
2. Obtain a copy of the code to update to (see the install section).
3. For each Replicante Core server:
   1. Install the new binary.
   2. Restart the process on the node.
   3. Check the logs to ensure everything works as expected.

Once the upgrade is complete you should review the configuration to enable new options and disable any deprecated features. Refer to the change log to know what was added and what was deprecated.

Changes to data schema

Any software that persist data needs to deal with changes to the schema as the software evolves. Replicante Core tries to avoid the need for migrations by gradually rolling out changes to the schema.

When the data schema needs to change:

1. A minor version is released to introduce the changes as optional:
   • New attributes are added and always set but expected to be missing.
   • Deprecated attributes are no longer used but still set.
2. As clusters are updated, stored data is updated to the new schema when it is updated by any operation.
3. A major version is released expecting the data to have the new schema:
   • New attributes are no longer optional and decoding data without them fails.
   • Deprecated attributes are no longer used or set.

Upgrading to major releases

Always run the latest minor release before upgrades to the next major release.

The approach above works because Replicante Core expires historical data and refreshes monitoring data. You may need to run the latest minor release until all data items are expired or refreshed.