before:
- /var/run/memcached is a bad default for a socket path, since its
parent directory must be writeable by memcached.
- Socket directory was not created by the module itself -> this was
left as a burden to the user?
- Having a static uid with a dynamic user name is not very useful.
after:
- Replace services.memcached.socket by a boolean flag. This simplifies
our code, since we do not have to check if the user specifies a
path with a parent directory that should be owned by memcached
(/run/memcached/memcached.sock -> /run/memcached).
- Remove fixed uid/gid allocation. The only file ever owned by the
daemon is the socket that will be recreated on every start.
Therefore user and group ids do not need to be static.
- only create the memcached user, if the user has not specified a
different one. The major use case for changing option is to allow
existing services (such as php-fpm) opening the local unix socket.
If we would unconditionally create a user that option would be
useless.
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
