Principals in Kafka are defined by a type and a name. The principal type will always be "User"
for the simple authorizer that is enabled by default, but custom authorizers can leverage different
principal types (such as to enable group or role-based ACLs). The
is used when you need to derive a different principal type from the authentication context, or when
you need to represent relations between different principals. For example, you could extend
in order to link a user principal to one or more role principals.
For custom extensions of
, there two key points to keep in mind:
1. To be compatible with the ACL APIs provided by Kafka (including the command line tool), each ACL
can only represent a permission granted to a single principal (consisting of a principal type and name).
It is possible to use richer ACL semantics, but you must implement your own mechanisms for adding
and removing ACLs.
2. In general,
extensions are only useful when the corresponding Authorizer
is also aware of the extension. If you have a
which derives user groups
from the authentication context (e.g. from an SSL client certificate), then you need a custom
authorizer which is capable of using the additional group information.