1. Is this for you?
charm-refresh is designed for in-place refreshes of stateful charmed applications.
Out-of-place upgrade
For some charms, it may be sufficient to only support "out-of-place" upgrades.
An "out-of-place" upgrade means to re-deploy the application instead of juju refreshing the existing application.
(For stateful charms, an "out-of-place" upgrade also often involves a backup of the old application and a restore to the new application—or some other method to transfer the state, such as asynchronous replication.)
If this is sufficient for your charm, do this instead—it is usually much simpler (from an implementation and a backwards compatibility perspective).
Stateless workload
For charms with a workload that is stateless, implementing and maintaining charm-refresh may have a greater cost than the value charm-refresh provides.
Because of its design for stateful workloads, charm-refresh may be more complex than what’s needed for stateless workloads.
However, charm-refresh may be useful for stateless workloads if any of this functionality is needed:
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refresh units one at a time to maintain high availability
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ability to rollback (in some situations) even if the charm code is raising an uncaught exception or the user refreshed to the incorrect charm revision or OCI resource
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run automatic checks before & during the refresh and automatically halt the refresh if any check fails
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coordinated refresh with other Juju applications