Add support for removing all l3 routers from agent

The neutron-ha-tool.py tool has the ability to rebalance routers on l3
agents, this adds the ability to remove all the routers from one l3
agent so it can be taken down for maintenance.  Just something that is a
minor change but quite handy to have available.

Also added the ability to read the region, if your neutron needs it.

Change-Id: I17d8f6f8c707dd6be0e64ccc2d5637b72b8ed392

files/default/neutron-ha-tool.py

@@ -38,7 +38,7 @@ def parse_args():
 
     # ensure environment has necessary items to authenticate
     for key in ['OS_TENANT_NAME', 'OS_USERNAME', 'OS_PASSWORD',
-                'OS_AUTH_URL']:
+                'OS_AUTH_URL', 'OS_REGION_NAME']:
         if key not in os.environ.keys():
             LOG.exception("Your environment is missing '%s'")
 
@@ -53,6 +53,8 @@ def parse_args():
                     help='Show routers associated with offline l3 agents')
     ap.add_argument('--l3-agent-migrate', action='store_true', default=False,
                     help='Migrate routers away from offline l3 agents')
+    ap.add_argument('--l3-agent-evacuate', default=None,
+                    help='Migrate routers away from a particular l3 agent')
     ap.add_argument('--l3-agent-rebalance', action='store_true', default=False,
                     help='Rebalance router count on all l3 agents')
     ap.add_argument('--replicate-dhcp', action='store_true', default=False,
@@ -93,6 +95,7 @@ def run(args):
                             tenant_name=os.environ['OS_TENANT_NAME'],
                             password=os.environ['OS_PASSWORD'],
                             endpoint_type='internalURL',
+                            region_name=os.environ['OS_REGION_NAME'],
                             insecure=args.insecure,
                             ca_cert=ca)
 
@@ -107,6 +110,11 @@ def run(args):
         LOG.info("Performing L3 Agent Migration for Offline L3 Agents")
         l3_agent_migrate(qclient, args.noop, args.now)
 
+    if args.l3_agent_evacuate:
+        LOG.info("Performing L3 Agent Evacuation from agent %s",
+                 args.l3_agent_evacuate)
+        l3_agent_evacuate(qclient, args.l3_agent_evacuate, args.noop)
+
     if args.l3_agent_rebalance:
         LOG.info("Rebalancing L3 Agent Router Count")
         l3_agent_rebalance(qclient, args.noop)
@@ -308,6 +316,56 @@ def l3_agent_migrate(qclient, noop=False, now=False):
                  migration_count)
 
 
+def l3_agent_evacuate(qclient, excludeagent, noop=False):
+    """
+    Retreive a list of routers scheduled on the listed agent, and move that
+    to another agent.
+
+    :param qclient: A neutronclient
+    :param noop: Optional noop flag
+    :param excludeagent: the name of the L3 agent to migrate routers from
+
+    """
+
+    agent_list = list_agents(qclient, agent_type='L3 agent')
+    target_list = target_agent_list(agent_list, 'L3 agent', excludeagent)
+
+    migration_count = 0
+
+    if len(target_list) < 1:
+        LOG.exception("There are no l3 agents alive to migrate "
+                      "routers onto")
+
+    agent_to_exclude = None
+    for agent in agent_list:
+        if agent.get('host', None) == excludeagent:
+            agent_to_exclude = agent
+            break
+
+    if not agent_to_exclude:
+        LOG.exception("Could not locate agent to evacuate")
+
+    agent_id = agent_to_exclude['id']
+    LOG.info("Querying agent_id=%s for routers to migrate", agent_id)
+    router_id_list = list_routers_on_l3_agent(qclient, agent_id)
+
+    for router_id in router_id_list:
+        target_id = random.choice(target_list)
+        LOG.info("Migrating router=%s to agent=%s",
+                 router_id, target_id)
+
+        try:
+            if not noop:
+                migrate_router(qclient, router_id, agent_id, target_id)
+        except Exception:
+            LOG.exception("There was an error migrating a router")
+            continue
+        migration_count += 1
+
+    LOG.info("%s routers required migration from L3 agent %s",
+             migration_count, excludeagent)
+
+
 def replicate_dhcp(qclient, noop=False):
     """
     Retrieve a network list and then probe each DHCP agent to ensure
@@ -524,6 +582,22 @@ def agent_alive_id_list(agent_list, agent_type):
             if agent['agent_type'] == agent_type and agent['alive'] is True]
 
 
+def target_agent_list(agent_list, agent_type, excludeagent):
+    """
+    Return a list of agents that are alive, excluding the one we want to
+    migrate from
+
+    :param agent_list: API response for list_agents()
+    :param agent_type: used to filter the type of agent
+    :param excludeagent: which agent should we exclude from the list
+
+    """
+    return [agent['id'] for agent in agent_list
+            if agent['agent_type'] == agent_type
+            and agent['alive']
+            and agent['host'] != excludeagent]
+
+
 def agent_dead_id_list(agent_list, agent_type):
     """
     Return a list of agents that are dead from an API list of agents