radvd: pass -m syslog to avoid thread lock for radvd 2.0+

Since radvd 2.0, the daemon does not use daemon_fork() function from
libdaemon, but instead calls Linux daemon() function directly. It also
passes (1, 1) arguments when logging method (-m) is either stderr (the
default) or stderr_syslog. The second argument's value = 1 means that
stderr is not closed and left there for (some) log messages.

For neutron, it means that corresponding execute() call that spawns
radvd and expects the invoked process to close stderr does not ever get
completed. The current thread that spawned radvd is locked waiting for
radvd to exit, which does not ever occur unless the process crashes or
receives a signal.

Since L3 agent gives exclusive access to updates queue for each router
to one of processing threads only, it means that the thread that got to
serve a radvd-powered subnet will not proceed and not update any new
ports or other changes to the router anymore.

Passing -m syslog makes radvd 2.0+ close stderr and return to execute()
caller, proceeding with router update processing. The same arguments
should work for old (pre 2.0) versions of radvd too, so passing them
unconditionally.

We could instead use -m logfile and pass appropriate -l <logfile>
argument to radvd to make it log to a log file located in router's
namespace storage path. Though that would be not in line with what
dnsmasq processes currently do for dhcp agent, where we log all messages
to syslog, so sticking to syslog for radvd for consistency.

Change-Id: I131db0639bc46d332ed48faa2bbe68a214264062
Closes-Bug: #1398779

diff --git a/neutron/agent/linux/ra.py b/neutron/agent/linux/ra.py
index 66fa0129f16da3ff87e986d95044af331a64564f..6bdfea57c5179f23a026f4eca344aae27abd8420 100644 (file)
--- a/neutron/agent/linux/ra.py
+++ b/neutron/agent/linux/ra.py
@@ -82,9 +82,15 @@ def _generate_radvd_conf(router_id, router_ports, dev_name_helper):
 
 def _spawn_radvd(router_id, radvd_conf, router_ns, root_helper):
     def callback(pid_file):
+        # we need to use -m syslog and f.e. not -m stderr (the default)
+        # or -m stderr_syslog so that radvd 2.0+ will close stderr and
+        # exit after daemonization; otherwise, the current thread will
+        # be locked waiting for result from radvd that won't ever come
+        # until the process dies
         radvd_cmd = ['radvd',
                      '-C', '%s' % radvd_conf,
-                     '-p', '%s' % pid_file]
+                     '-p', '%s' % pid_file,
+                     '-m', 'syslog']
         return radvd_cmd
 
     radvd = external_process.ProcessManager(cfg.CONF,

diff --git a/neutron/tests/unit/test_l3_agent.py b/neutron/tests/unit/test_l3_agent.py
index 54ae156cf6befc1765f8d15edc91dca83640b33b..339dae14eca651ef02a6ad49748330c8fe7f22dc 100644 (file)
--- a/neutron/tests/unit/test_l3_agent.py
+++ b/neutron/tests/unit/test_l3_agent.py
@@ -27,6 +27,7 @@ from neutron.agent.common import config as agent_config
 from neutron.agent import l3_agent
 from neutron.agent import l3_ha_agent
 from neutron.agent.linux import interface
+from neutron.agent.linux import ra
 from neutron.common import config as base_config
 from neutron.common import constants as l3_constants
 from neutron.common import exceptions as n_exc
@@ -2315,6 +2316,38 @@ vrrp_instance VR_1 {
         self.assertFalse(nat.add_rule.called)
         nat.clear_rules_by_tag.assert_called_once_with('floating_ip')
 
+    def test_spawn_radvd(self):
+        router = prepare_router_data()
+
+        conffile = '/fake/radvd.conf'
+        pidfile = '/fake/radvd.pid'
+        agent = l3_agent.L3NATAgent(HOSTNAME, self.conf)
+
+        # we don't want the whole process manager to be mocked to be
+        # able to catch execute() calls
+        self.external_process_p.stop()
+        self.ip_cls_p.stop()
+
+        get_pid_file_name = ('neutron.agent.linux.external_process.'
+                             'ProcessManager.get_pid_file_name')
+        with mock.patch('neutron.agent.linux.utils.execute') as execute:
+            with mock.patch(get_pid_file_name) as get_pid:
+                get_pid.return_value = pidfile
+                ra._spawn_radvd(router['id'],
+                                conffile,
+                                agent.get_ns_name(router['id']),
+                                self.conf.root_helper)
+            cmd = execute.call_args[0][0]
+
+        self.assertIn('radvd', cmd)
+
+        _join = lambda *args: ' '.join(args)
+
+        cmd = _join(*cmd)
+        self.assertIn(_join('-C', conffile), cmd)
+        self.assertIn(_join('-p', pidfile), cmd)
+        self.assertIn(_join('-m', 'syslog'), cmd)
+
 
 class TestL3AgentEventHandler(base.BaseTestCase):