Append 'Openstack-Request-Id' header to the response

This patch will append request_id to response headers. This is helpful
for admin to track problems across projects.

Accroding to OpenStack HTTP Header Guidelines, use
'Openstack-Request-Id' instead of 'X-Openstack-Request-ID'.

According the suggestions from API WG, a microversion is not needed here.

Change-Id: Ica067aff19fe17052fcaf9c7384c9da7d1f7997d
Partial-Bug: #1505119

ironic/api/hooks.py

@@ -89,6 +89,15 @@ class ContextHook(hooks.PecanHook):
             show_password=show_password,
             **creds)
 
+    def after(self, state):
+        if state.request.context == {}:
+            # An incorrect url path will not create RequestContext
+            return
+        # NOTE(lintan): RequestContext will generate a request_id if no one
+        # passing outside, so it always contain a request_id.
+        request_id = state.request.context.request_id
+        state.response.headers['Openstack-Request-Id'] = request_id
+
 
 class RPCHook(hooks.PecanHook):
     """Attach the rpcapi object to the request so controllers can get to it."""

ironic/tests/unit/api/test_hooks.py

@@ -285,6 +285,26 @@ class TestContextHook(base.BaseApiTest):
             is_admin=False,
             roles=headers['X-Roles'].split(','))
 
+    @mock.patch.object(context, 'RequestContext')
+    def test_context_hook_after_add_request_id(self, mock_ctx):
+        headers = fake_headers(admin=True)
+        reqstate = FakeRequestState(headers=headers)
+        reqstate.set_context()
+        reqstate.request.context.request_id = 'fake-id'
+        context_hook = hooks.ContextHook(None)
+        context_hook.after(reqstate)
+        self.assertIn('Openstack-Request-Id',
+                      reqstate.response.headers)
+        self.assertEqual(
+            'fake-id',
+            reqstate.response.headers['Openstack-Request-Id'])
+
+    def test_context_hook_after_miss_context(self):
+        response = self.get_json('/bad/path',
+                                 expect_errors=True)
+        self.assertNotIn('Openstack-Request-Id',
+                         response.headers)
+
 
 class TestTrustedCallHook(base.BaseApiTest):
     def test_trusted_call_hook_not_admin(self):

releasenotes/notes/opentack-baremetal-request-id-daa72b785eaaaa8d.yaml

@@ -0,0 +1,4 @@
+---
+features:
+  - Append request_id as ``Openstack-Request-Id`` header to the response.
+