Alluxio Developer Tip: Why am I seeing the error “User yarn is not configured for any impersonation. impersonationUser: foo?”

Impersonation is simply the ability for one user to act on behalf of another user. For example, say user ‘yarn’ has the credentials to connect to a service, but user ‘foo’ does not. Therefore, user ‘foo’ would never be able to access the service. However, user ‘yarn’ can access the service and impersonate (act on behalf of) user ‘foo’, allowing access to user ‘foo’. Therefore, impersonation enables one user to access a service on behalf of another user.
The impersonation feature defines how users can act on behalf of other users. Therefore, it is important to know who the users are.