Add --print option to force printing

The use case for --print is an administrator wanting to view the
metadata that os-collect-config sees without running any commands.

Fixes bug #1213195

Change-Id: I0251f2c70574aeaa79997ce822d2a5ffbe08e345

os_collect_config/collect.py

@@ -62,6 +62,11 @@ opts = [
                 default=False,
                 help='Pass this to force running the command even if nothing'
                 ' has changed.'),
+    cfg.BoolOpt('print', dest='print_only',
+                default=False,
+                help='Query normally, print the resulting configs as a json'
+                ' map, and exit immediately without running command if it is'
+                ' configured.'),
 ]
 
 CONF = cfg.CONF
@@ -183,12 +188,13 @@ def __main__(args=sys.argv, requests_impl_map=None):
     config_files = CONF.config_file
     config_hash = getfilehash(config_files)
     while True:
+        store_and_run = bool(CONF.command and not CONF.print_only)
         (any_changed, content) = collect_all(
             cfg.CONF.collectors,
-            store=bool(CONF.command),
+            store=store_and_run,
             requests_impl_map=requests_impl_map)
-        if CONF.command:
-            if any_changed or cfg.CONF.force:
+        if store_and_run:
+            if any_changed or CONF.force:
                 # ignore HUP now since we will reexec after commit anyway
                 signal.signal(signal.SIGHUP, signal.SIG_IGN)
                 try:

os_collect_config/tests/test_collect.py

@@ -192,6 +192,7 @@ class TestCollect(testtools.TestCase):
             '--config-file', '/dev/null',
             '--print-cachedir',
         ]
+
         output = self.useFixture(fixtures.StringStream('stdout'))
         self.useFixture(
             fixtures.MonkeyPatch('sys.stdout', output.stream))
@@ -199,6 +200,41 @@ class TestCollect(testtools.TestCase):
         cache_dir = output.getDetails()['stdout'].as_text().strip()
         self.assertEquals(fake_cachedir.path, cache_dir)
 
+    def test_main_print_only(self):
+        cache_dir = self.useFixture(fixtures.TempDir())
+        fake_metadata = _setup_local_metadata(self)
+        args = [
+            'os-collect-config',
+            '--command', 'bar',
+            '--cachedir', cache_dir.path,
+            '--config-file', '/dev/null',
+            '--print',
+            '--cfn-metadata-url',
+            'http://127.0.0.1:8000/v1/',
+            '--cfn-stack-name',
+            'foo',
+            '--cfn-path',
+            'foo.Metadata',
+            '--cfn-access-key-id',
+            '0123456789ABCDEF',
+            '--cfn-secret-access-key',
+            'FEDCBA9876543210',
+            '--heat_local-path', fake_metadata,
+        ]
+
+        def fake_popen(args):
+            self.fail('Called command instead of printing')
+        self.useFixture(fixtures.FakePopen(fake_popen))
+        output = self.useFixture(fixtures.StringStream('stdout'))
+        self.useFixture(
+            fixtures.MonkeyPatch('sys.stdout', output.stream))
+        self._call_main(args)
+        out_struct = json.loads(output.getDetails()['stdout'].as_text())
+        self.assertThat(out_struct, matchers.IsInstance(dict))
+        self.assertIn('cfn', out_struct)
+        self.assertIn('heat_local', out_struct)
+        self.assertIn('ec2', out_struct)
+
     def test_main_invalid_collector(self):
         fake_args = ['os-collect-config', 'invalid']
         self.assertRaises(exc.InvalidArguments, self._call_main, fake_args)