Add --print-cachedir option

The option allows other programs to find the cache directory and files
without having access to OS_CONFIG_FILES.

Change-Id: Iad87efb65ea4db387e94160376c9eaf956fff413

os_collect_config/collect.py

@@ -55,6 +55,9 @@ opts = [
     cfg.FloatOpt('polling-interval', short='i', default=300,
                  help='When running continuously, pause this many seconds'
                       ' between collecting data.'),
+    cfg.BoolOpt('print-cachedir',
+                default=False,
+                help='Print out the value of cachedir and exit immediately.'),
 ]
 
 CONF = cfg.CONF
@@ -161,6 +164,10 @@ def __main__(args=sys.argv, requests_impl_map=None):
     if not log.getLogger(None).logger.handlers:
         log.setup("os-collect-config")
 
+    if CONF.print_cachedir:
+        print(CONF.cachedir)
+        return
+
     unknown_collectors = set(CONF.collectors) - set(DEFAULT_COLLECTORS)
     if unknown_collectors:
         raise exc.InvalidArguments(

os_collect_config/tests/test_collect.py

@@ -156,6 +156,21 @@ class TestCollect(testtools.TestCase):
         self.assertIn('ec2', out_struct)
         self.assertIn('cfn', out_struct)
 
+    def test_main_print_cachedir(self):
+        fake_cachedir = self.useFixture(fixtures.TempDir())
+        fake_args = [
+            'os-collect-config',
+            '--cachedir', fake_cachedir.path,
+            '--config-file', '/dev/null',
+            '--print-cachedir',
+        ]
+        output = self.useFixture(fixtures.StringStream('stdout'))
+        self.useFixture(
+            fixtures.MonkeyPatch('sys.stdout', output.stream))
+        self._call_main(fake_args)
+        cache_dir = output.getDetails()['stdout'].as_text().strip()
+        self.assertEquals(fake_cachedir.path, cache_dir)
+
     def test_main_invalid_collector(self):
         fake_args = ['os-collect-config', 'invalid']
         self.assertRaises(exc.InvalidArguments, self._call_main, fake_args)