When installing Linkerd, a user may override default settings, or may
explicitly configure defaults. Consider install options like `--ha
--controller-replicas=4` -- the `--ha` flag sets a new default value for
the controller-replicas, and then we override it.
When we later upgrade this cluster, how can we know how to configure the
cluster?
We could store EnableHA and ControllerReplicas configurations in the
config, but what if, in a later upgrade, the default value changes? How
can we know whether the user specified an override or just used the
default?
To solve this, we add an `Install` message into a new config.
This message includes (at least) the CLI flags used to invoke
install.
upgrade does not specify defaults for install/proxy-options fields and,
instead, uses the persisted install flags to populate default values,
before applying overrides from the upgrade invocation.
This change breaks the protobuf compatibility by altering the
`installation_uuid` field introduced in 9c442f6885.
Because this change was not yet released (even in an edge release), we
feel that it is safe to break.
Fixes https://github.com/linkerd/linkerd2/issues/2574
Because the linkerd-config resource is created after pods that require
it, they can be started before the files are mounted, causing the pods
to restart integration tests to fail.
If we extract the config into its own template file, it can be inserted
before pods are created.
Oliver Gould