Server Roles: Backend plugin to query roles and attributes

`serverroles` backend consumes the role/attribute instances defined in
`ipaserver/servroles.py` module to provide low-level API for querying
role/attribute status in the topology. This plugin shall be used to implement
higher-level API commands.

https://www.freeipa.org/page/V4/Server_Roles
https://fedorahosted.org/freeipa/ticket/5181

Reviewed-By: Jan Cholasta <jcholast@redhat.com>
Reviewed-By: Martin Basti <mbasti@redhat.com>
Reviewed-By: Pavel Vomacka <pvomacka@redhat.com>

ipaserver/plugins/serverroles.py

@@ -0,0 +1,149 @@
+#
+# Copyright (C) 2016 FreeIPA Contributors see COPYING for license
+#
+
+
+"""
+serverroles backend
+=======================================
+
+The `serverroles` backend has access to all roles and attributes stored in
+module-level lists exposed in `ipaserver/servroles.py` module. It uses these
+lists to populate populate its internal stores with instances of the
+roles/attributes. The information contained in them can be accessed by
+the following methods:
+
+    *api.Backend.serverroles.server_role_search(
+            server_server=None, role_servrole=None status=None)
+        search for roles matching the given substrings and return the status of
+        the matched roles. Optionally filter the result by role status. If
+        `server_erver` is not None, the search is limited to a single master.
+        Otherwise, the status is computed for all masters in the topology. If
+        `role_servrole` is None, the all configured roled are queried
+
+    *api.Backend.serverroles.server_role_retrieve(server_server, role_servrole)
+        retrieve the status of a single role on a given master
+
+    *api.Backend.serverroles.config_retrieve(role_servrole)
+        return a configuration object given role name. This object is a
+        dictionary containing a list of enabled masters and all attributes
+        associated with the role along with master(s) on which they are set.
+
+    *api.Backend.serverroles.config_update(**attrs_values)
+        update configuration object. Since server roles are currently
+        immutable, only attributes can be set
+
+Note that attribute/role names are searched/matched case-insensitively. Also
+note that the `serverroles` backend does not create/destroy any LDAP connection
+by itself, so make sure `ldap2` backend connections are taken care of
+in the calling code
+"""
+
+
+import six
+
+from ipalib import errors, _
+from ipalib.backend import Backend
+from ipalib.plugable import Registry
+from ipaserver.servroles import (attribute_instances, ENABLED, role_instances)
+
+
+if six.PY3:
+    unicode = str
+
+
+register = Registry()
+
+
+@register()
+class serverroles(Backend):
+    """
+    This Backend can be used to query various information about server roles
+    and attributes configured in the topology.
+    """
+
+    def __init__(self, api_instance):
+        super(serverroles, self).__init__(api_instance)
+
+        self.role_names = {
+            obj.name.lower(): obj for obj in role_instances}
+
+        self.attributes = {
+            attr.attr_name: attr for attr in attribute_instances}
+
+    def _get_role(self, role_name):
+        key = role_name.lower()
+
+        try:
+            return self.role_names[key]
+        except KeyError:
+            raise errors.NotFound(
+                reason=_("{role}: role not found".format(role=role_name)))
+
+    def _get_enabled_masters(self, role_name):
+        role = self._get_role(role_name)
+
+        enabled_masters = [
+            r[u'server_server'] for r in role.status(self.api, server=None) if
+            r[u'status'] == ENABLED]
+
+        return {role.attr_name: enabled_masters}
+
+    def _get_assoc_attributes(self, role_name):
+        role = self._get_role(role_name)
+        assoc_attributes = {
+            name: attr for name, attr in self.attributes.items() if
+            attr.associated_role is role}
+
+        if not assoc_attributes:
+            raise NotImplementedError(
+                "Role {} has no associated attribute to set".format(role.name))
+
+        return assoc_attributes
+
+    def server_role_search(self, server_server=None, role_servrole=None,
+                           status=None):
+        if role_servrole is None:
+            found_roles = self.role_names.values()
+        else:
+            try:
+                found_roles = [self._get_role(role_servrole)]
+            except errors.NotFound:
+                found_roles = []
+
+        result = []
+        for found_role in found_roles:
+            role_status = found_role.status(self.api, server=server_server)
+
+            result.extend(role_status)
+
+        if status is not None:
+            return [r for r in result if r[u'status'] == status]
+
+        return result
+
+    def server_role_retrieve(self, server_server, role_servrole):
+        return self._get_role(role_servrole).status(
+            self.api, server=server_server)
+
+    def config_retrieve(self, servrole):
+        result = self._get_enabled_masters(servrole)
+
+        try:
+            assoc_attributes = self._get_assoc_attributes(servrole)
+        except NotImplementedError:
+            return result
+
+        result.update(
+            {name: attr.get(self.api) for name, attr in
+             assoc_attributes.items()})
+
+        return result
+
+    def config_update(self, **attrs_values):
+        for attr, value in attrs_values.items():
+            try:
+                self.attributes[attr].set(self.api, value)
+            except KeyError:
+                raise errors.NotFound(
+                    reason=_('{attr}: no such attribute'.format(attr=attr)))