Add option to use JSON formatter

This adds the use_json option, which will use the JSON formatter
instead of the deafult ContextFormatter if set.

Closes-Bug: #1729331
Change-Id: I1b7b7b9e66215e8e1c59a2c0a37cb0abaebf228a

oslo_log/_options.py

@@ -97,6 +97,10 @@ logging_cli_opts = [
                default='LOG_USER',
                help='Syslog facility to receive log lines. '
                     + _IGNORE_MESSAGE),
+    cfg.BoolOpt('use-json',
+                default=False,
+                help='Use JSON formatting for logging. '
+                     + _IGNORE_MESSAGE),
 ]
 
 generic_log_opts = [

oslo_log/log.py

@@ -383,11 +383,15 @@ def _setup_logging_from_conf(conf, project, version):
         log_root.addHandler(syslog_handler)
 
     datefmt = conf.log_date_format
-    for handler in log_root.handlers:
-        handler.setFormatter(formatters.ContextFormatter(project=project,
-                                                         version=version,
-                                                         datefmt=datefmt,
-                                                         config=conf))
+    if not conf.use_json:
+        for handler in log_root.handlers:
+            handler.setFormatter(formatters.ContextFormatter(project=project,
+                                                             version=version,
+                                                             datefmt=datefmt,
+                                                             config=conf))
+    else:
+        for handler in log_root.handlers:
+            handler.setFormatter(formatters.JSONFormatter(datefmt=datefmt))
     _refresh_root_level(conf.debug)
 
     for pair in conf.default_log_levels:

oslo_log/tests/unit/test_log.py

@@ -1496,6 +1496,7 @@ class LogConfigOptsTestCase(BaseTestCase):
                          self.CONF.log_date_format)
 
         self.assertEqual(False, self.CONF.use_syslog)
+        self.assertEqual(False, self.CONF.use_json)
 
     def test_log_file(self):
         log_file = '/some/path/foo-bar.log'
@@ -1553,6 +1554,15 @@ class LogConfigOptsTestCase(BaseTestCase):
             self.assertIsInstance(formatter,
                                   formatters.ContextFormatter)
 
+    def test_json_formatter(self):
+        self.CONF(['--use-json'])
+        log._setup_logging_from_conf(self.CONF, 'test', 'test')
+        logger = log._loggers[None].logger
+        for handler in logger.handlers:
+            formatter = handler.formatter
+            self.assertIsInstance(formatter,
+                                  formatters.JSONFormatter)
+
     def test_handlers_cleanup(self):
         """Test that all old handlers get removed from log_root."""
         old_handlers = [log.handlers.ColorHandler(),