Re-execute after commands and on SIGHUP

After we have run a command and committed, re-execute ourselves. This
ensures that we will get any configurations that may have come from
underlying commands. Also re-execute if os-collect-config is sent HUP.

Change-Id: I87b4d8ce44fcbc9458a3a4fbb2445e4c9d0ad4e7

os_collect_config/collect.py

@@ -15,6 +15,7 @@
 
 import json
 import os
+import signal
 import subprocess
 import sys
 import time
@@ -114,7 +115,23 @@ def collect_all(collectors, store=False, requests_impl_map=None):
     return (any_changed, paths_or_content)
 
 
+def reexec_self(signal=None, frame=None):
+    if signal:
+        logger.info('Signal received. Re-executing %s' % sys.argv)
+    # Close all but stdin/stdout/stderr
+    os.closerange(3, 255)
+    os.execv(sys.argv[0], sys.argv)
+
+
+def call_command(files, command):
+    env = dict(os.environ)
+    env["OS_CONFIG_FILES"] = ':'.join(files)
+    logger.info("Executing %s" % command)
+    subprocess.call(CONF.command, env=env, shell=True)
+
+
 def __main__(args=sys.argv, requests_impl_map=None):
+    signal.signal(signal.SIGHUP, reexec_self)
     setup_conf()
     CONF(args=args[1:], prog="os-collect-config")
 
@@ -133,12 +150,13 @@ def __main__(args=sys.argv, requests_impl_map=None):
             requests_impl_map=requests_impl_map)
         if CONF.command:
             if any_changed:
-                env = dict(os.environ)
-                env["OS_CONFIG_FILES"] = ':'.join(content)
-                logger.info("Executing %s" % CONF.command)
-                subprocess.call(CONF.command, env=env, shell=True)
+                # ignore HUP now since we will reexec after commit anyway
+                signal.signal(signal.SIGHUP, signal.SIG_IGN)
+                call_command(content, CONF.command)
                 for collector in cfg.CONF.collectors:
                     cache.commit(collector)
+                if not CONF.one_time:
+                    reexec_self()
             else:
                 logger.debug("No changes detected.")
             if CONF.one_time:

os_collect_config/tests/test_collect.py

@@ -18,8 +18,11 @@ import extras
 import fixtures
 import json
 import os
-from oslo.config import cfg
+import signal
+import sys
 import tempfile
+
+from oslo.config import cfg
 import testtools
 from testtools import matchers
 
@@ -39,6 +42,7 @@ def _setup_local_metadata(test_case):
 
 
 class TestCollect(testtools.TestCase):
+
     def setUp(self):
         super(TestCollect, self).setUp()
         self.useFixture(fixtures.FakeLogger())
@@ -235,8 +239,35 @@ class TestCollectAll(testtools.TestCase):
 
 
 class TestConf(testtools.TestCase):
+
     def test_setup_conf(self):
         collect.setup_conf()
         self.assertEquals('/var/run/os-collect-config', cfg.CONF.cachedir)
         self.assertTrue(extras.safe_hasattr(cfg.CONF, 'ec2'))
         self.assertTrue(extras.safe_hasattr(cfg.CONF, 'cfn'))
+
+
+class TestHup(testtools.TestCase):
+
+    def setUp(self):
+        super(TestHup, self).setUp()
+        self.log = self.useFixture(fixtures.FakeLogger())
+
+        def fake_closerange(low, high):
+            self.assertEquals(3, low)
+            self.assertEquals(255, high)
+
+        def fake_execv(path, args):
+            self.assertEquals(sys.argv[0], path)
+            self.assertEquals(sys.argv, args)
+
+        self.useFixture(fixtures.MonkeyPatch('os.execv', fake_execv))
+        self.useFixture(fixtures.MonkeyPatch('os.closerange', fake_closerange))
+
+    def test_reexec_self_signal(self):
+        collect.reexec_self(signal.SIGHUP, None)
+        self.assertIn('Signal received', self.log.output)
+
+    def test_reexec_self(self):
+        collect.reexec_self()
+        self.assertNotIn('Signal received', self.log.output)