py3: Make seamless reloads work

Starting with Python 3.4, newly-created file descriptors are non-inheritable
[0], which causes trouble when we try to use a pipe for IPC. Fortunately, the
same PEP that implemented this change *also* provided a new API to mark file
descriptors as being inheritable -- so just do that.

While we're at it,

* Fix up the probe tests to work on py3
* Fix up the probe tests to work when policy-0 is erasure-coded
* Decode the bytes read so py3 doesn't log a b'pid'
* Log a warning if the read() is empty; something surely went wrong
  in the re-exec

[0] https://www.python.org/dev/peps/pep-0446/

Change-Id: I2a8a9f3dc78abb99bf9cbcf6b44c32ca644bb07b
Related-Change: I3e5229d2fb04be67e53533ff65b0870038accbb7

swift/common/wsgi.py

@@ -1288,6 +1288,9 @@ def run_wsgi(conf_path, app_section, *args, **kwargs):
             myself = os.path.realpath(sys.argv[0])
             logger.info("Old server PID=%d re'execing as: %r",
                         orig_server_pid, [myself] + list(sys.argv))
+            if hasattr(os, 'set_inheritable'):
+                # See https://www.python.org/dev/peps/pep-0446/
+                os.set_inheritable(write_fd, True)
             os.execv(myself, sys.argv)
             logger.error('Somehow lived past os.execv()?!')
             exit('Somehow lived past os.execv()?!')
@@ -1299,12 +1302,19 @@ def run_wsgi(conf_path, app_section, *args, **kwargs):
                         os.getpid(), orig_server_pid)
             try:
                 got_pid = os.read(read_fd, 30)
-                logger.info('Old server temporary child PID=%d notified '
-                            'to shutdown old listen sockets by PID=%s',
-                            os.getpid(), got_pid)
             except Exception as e:
                 logger.warning('Unexpected exception while reading from '
                                'pipe:', exc_info=True)
+            else:
+                got_pid = got_pid.decode('ascii')
+                if got_pid:
+                    logger.info('Old server temporary child PID=%d notified '
+                                'to shutdown old listen sockets by PID=%s',
+                                os.getpid(), got_pid)
+                else:
+                    logger.warning('Old server temporary child PID=%d *NOT* '
+                                   'notified to shutdown old listen sockets; '
+                                   'the pipe just *died*.', os.getpid())
             try:
                 os.close(read_fd)
             except Exception:

test/probe/test_signals.py

@@ -27,7 +27,6 @@ from uuid import uuid4
 
 from six.moves import http_client as httplib
 
-from swift.common.storage_policy import POLICIES
 from swift.common.ring import Ring
 from swift.common.manager import Manager
 
@@ -230,9 +229,9 @@ class TestObjectServerReloadBase(TestWSGIServerProcessHandling):
     PID_TIMEOUT = 35
 
     def get_ip_port(self):
-        policy = random.choice(list(POLICIES))
-        policy.load_ring('/etc/swift')
-        self.ring_node = random.choice(policy.object_ring.get_part_nodes(1))
+        self.policy.load_ring('/etc/swift')
+        self.ring_node = random.choice(
+            self.policy.object_ring.get_part_nodes(1))
         return self.ring_node['ip'], self.ring_node['port']
 
     def start_write_req(self, conn, suffix):
@@ -240,7 +239,8 @@ class TestObjectServerReloadBase(TestWSGIServerProcessHandling):
             self.ring_node['device'], self.account, self.container, suffix),
             headers={'X-Timestamp': str(time.time()),
                      'Content-Type': 'application/octet-string',
-                     'Content-Length': len(self.BODY)})
+                     'Content-Length': len(self.BODY),
+                     'X-Backend-Storage-Policy-Index': str(self.policy.idx)})
 
     def finish_write_req(self, conn):
         conn.send(self.BODY)
@@ -250,12 +250,12 @@ class TestObjectServerReloadBase(TestWSGIServerProcessHandling):
         got_body = resp.read()
         self.assertEqual(resp.status // 100, 2, 'Got status %d; %r' %
                          (resp.status, got_body))
-        self.assertEqual('', got_body)
+        self.assertEqual(b'', got_body)
         return resp
 
 
 class TestObjectServerReload(OldReloadMixin, TestObjectServerReloadBase):
-    BODY = 'test-object' * 10
+    BODY = b'test-object' * 10
 
     def test_object_reload(self):
         self._check_reload()
@@ -263,7 +263,7 @@ class TestObjectServerReload(OldReloadMixin, TestObjectServerReloadBase):
 
 class TestObjectServerReloadSeamless(SeamlessReloadMixin,
                                      TestObjectServerReloadBase):
-    BODY = 'test-object' * 10
+    BODY = b'test-object' * 10
 
     def test_object_reload_seamless(self):
         self._check_reload()
@@ -331,12 +331,12 @@ class TestProxyServerReloadBase(TestWSGIServerProcessHandling):
         got_body = resp.read()
         self.assertEqual(resp.status // 100, 2, 'Got status %d; %r' %
                          (resp.status, got_body))
-        self.assertEqual('', got_body)
+        self.assertEqual(b'', got_body)
         return resp
 
 
 class TestProxyServerReload(OldReloadMixin, TestProxyServerReloadBase):
-    BODY = 'proxy' * 10
+    BODY = b'proxy' * 10
 
     def test_proxy_reload(self):
         self._check_reload()
@@ -344,7 +344,7 @@ class TestProxyServerReload(OldReloadMixin, TestProxyServerReloadBase):
 
 class TestProxyServerReloadSeamless(SeamlessReloadMixin,
                                     TestProxyServerReloadBase):
-    BODY = 'proxy-seamless' * 10
+    BODY = b'proxy-seamless' * 10
 
     def test_proxy_reload_seamless(self):
         self._check_reload()