It will allow the following:
* when connectivity is limited (saturated linnks between DCs), only one
single request to refresh an ACL will be sent to ACL master DC instead
of statcking ACL refresh queries
* when extend-cache is used for ACL, do not wait for result, but refresh
the ACL asynchronously, so no delay is not impacting slave DC
* When extend-cache is not used, keep the existing blocking mechanism,
but only send a single refresh request.
This will fix https://github.com/hashicorp/consul/issues/3524
The error handling of the ACL code relies on the presence of certain
magic error messages. Since the error values are sent via RPC between
older and newer consul agents we cannot just replace the magic values
with typed errors and switch to type checks since this would break
compatibility with older clients.
Therefore, this patch moves all magic ACL error messages into the acl
package and provides default error values and helper functions which
determine the type of error.
* Moves magic check and service constants into shared structs package.
* Removes the "consul" service from local state.
Since this service is added by the leader, it doesn't really make sense to
also keep it in local state (which requires special ACLs to configure), and
requires a bunch of special cases in the local state logic. This requires
fewer special cases and makes ACL bootstrapping cleaner.
* Makes coordinate update ACL log message a warning, similar to other AE warnings.
* Adds much more detailed examples for bootstrapping ACLs.
This can hopefully replace https://gist.github.com/slackpad/d89ce0e1cc0802c3c4f2d84932fa3234.