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[Raphaël Badin <raphael.badin@xxxxxxxxxxxxx>]

Raphaël Badin has proposed merging lp:~rvb/maas/maas-dns2 into lp:maas.

Requested reviews:
  Launchpad code reviewers (launchpad-reviewers)

For more details, see:
https://code.launchpad.net/~rvb/maas/maas-dns2/+merge/114707

This branch adds a new method get_hostname_ip_mapping to DHCPLease.objects.  This method returns a mapping hostname -> ip for all the nodes in the given node group by considering the valid leases (from the table maasserver_dhcplease) for the first interface of each node.

This method will be used to populate the DNS zone files.

= Pre-imp =

This was discussed on IRC with Gavin and Jeroen.

= Notes =

I don't think it's possible to avoid the subquery given the fact that we have to consider only the first interface for all the nodes... but I'm happy to be proven wrong.
-- 
https://code.launchpad.net/~rvb/maas/maas-dns2/+merge/114707
Your team Launchpad code reviewers is requested to review the proposed merge of lp:~rvb/maas/maas-dns2 into lp:maas.

=== modified file 'src/maasserver/models/dhcplease.py'
--- src/maasserver/models/dhcplease.py	2012-07-11 04:14:08 +0000
+++ src/maasserver/models/dhcplease.py	2012-07-12 19:15:39 +0000
@@ -96,6 +96,37 @@
         self._delete_obsolete_leases(nodegroup, leases)
         self._add_missing_leases(nodegroup, leases)
 
+    def get_hostname_ip_mapping(self, nodegroup):
+        """Return a mapping {hostnames -> ips} for the currently leased
+        IP addresses for the nodes in `nodegroup`.
+
+        This will consider only the first interface (i.e. the first
+        MAC Address) associated with each node withing the given
+        `nodegroup`.
+        """
+        cursor = connection.cursor()
+        # The subquery fetches the IDs of the first MAC Address for
+        # all the nodes in this nodegroup.
+        # Then the main query returns the hostname -> ip mapping for
+        # these MAC Addresses.
+        cursor.execute("""
+        SELECT hostname, ip
+        FROM maasserver_macaddress as mac,
+             maasserver_node as node,
+             maasserver_dhcplease as lease
+        WHERE mac.id IN (
+            SELECT DISTINCT ON (node_id) mac.id
+            FROM maasserver_macaddress as mac,
+                 maasserver_node as node
+            WHERE node.nodegroup_id = %s AND mac.node_id = node.id
+            ORDER BY node_id, mac.created
+        )
+        AND mac.node_id = node.id
+        AND mac.mac_address = lease.mac
+        AND lease.nodegroup_id = %s
+        """ % (nodegroup.id, nodegroup.id))
+        return dict(cursor.fetchall())
+
 
 class DHCPLease(CleanSave, Model):
     """A known mapping of an IP address to a MAC address.

=== modified file 'src/maasserver/tests/test_dhcplease.py'
--- src/maasserver/tests/test_dhcplease.py	2012-07-10 17:28:42 +0000
+++ src/maasserver/tests/test_dhcplease.py	2012-07-12 19:15:39 +0000
@@ -134,3 +134,41 @@
                 new_ip: mac1,
             },
             map_leases(nodegroup))
+
+    def test_get_hostname_ip_mapping_returns_mapping(self):
+        nodegroup = factory.make_node_group()
+        expected_mapping = {}
+        for i in range(3):
+            node = factory.make_node(
+                nodegroup=nodegroup, set_hostname=True)
+            mac = factory.make_mac_address(node=node)
+            factory.make_mac_address(node=node)
+            lease = factory.make_dhcp_lease(
+                nodegroup=nodegroup, mac=mac.mac_address)
+            expected_mapping[node.hostname] = lease.ip
+        mapping = DHCPLease.objects.get_hostname_ip_mapping(nodegroup)
+        self.assertEqual(expected_mapping, mapping)
+
+    def test_get_hostname_ip_mapping_considers_only_first_mac(self):
+        nodegroup = factory.make_node_group()
+        node = factory.make_node(
+            nodegroup=nodegroup, set_hostname=True)
+        factory.make_mac_address(node=node)
+        second_mac = factory.make_mac_address(node=node)
+        # Create a lease for the second MAC Address.
+        factory.make_dhcp_lease(
+            nodegroup=nodegroup, mac=second_mac.mac_address)
+        mapping = DHCPLease.objects.get_hostname_ip_mapping(nodegroup)
+        self.assertEqual({}, mapping)
+
+    def test_get_hostname_ip_mapping_considers_given_nodegroup(self):
+        nodegroup = factory.make_node_group()
+        node = factory.make_node(
+            nodegroup=nodegroup, set_hostname=True)
+        mac = factory.make_mac_address(node=node)
+        factory.make_dhcp_lease(
+            nodegroup=nodegroup, mac=mac.mac_address)
+        another_nodegroup = factory.make_node_group()
+        mapping = DHCPLease.objects.get_hostname_ip_mapping(
+            another_nodegroup)
+        self.assertEqual({}, mapping)