Previously the consul_keys resource did double-duty as both a reader and
writer of values from the Consul key/value store, but that made its
interface rather confusing and complex, as well as having all of the other
general problems associated with read-only resources.
Here we split the functionality such that reading is done with the
consul_keys data source while writing is done with the consul_keys
resource.
The old read behavior of the resource is still supported, but it's no
longer documented (except as a deprecation note) and will generate
deprecation warnings when used.
In future it should be possible to simplify the consul_keys resource by
removing all of the read support, but that is deferred for now to give
users a chance to gracefully migrate to the new data source.
This new resource is an alternative to consul_keys that manages all keys
under a given prefix, rather than arbitrary single keys across the entire
store.
The key advantage of this resource over consul_keys is that it is able to
detect and delete keys that are added outside of Terraform, whereas
consul_keys is only able to detect changes to keys it is explicitly
managing.
Previously this resource managed the set of keys as a whole rather than
the individual keys, and so it was unable to recognize when a particular
managed key is removed and delete just that one key from Consul.
Here this is addressed by recognizing that each key actually has its own
lifecycle, and detecting when individual keys are added and removed
without replacing the entire consul_keys instance.
Additionally this restores the behavior of updating the "value" attribute
on read, but restricts it only to blocks that already had a value so as
to avoid the quirkiness seen previously when we updated blocks that were
intended to be read-only. Updating the value is important now, because we
rely on this to detect and repair discrepancies between values stored in
Consul and values given in the configuration.
This change produces a change in the handling of the "delete" attribute.
Before it was considered only when the entire consul_keys resource was
deleted, but now it is considered also when a particular key block is
removed from within a resource.
Seth Vargo