issue #373: parse the child process wait status

Don't log the raw waitpid() result, convert it to a useful string first.

mitogen/parent.py

@@ -93,6 +93,12 @@ SYS_EXECUTABLE_MSG = (
 )
 _sys_executable_warning_logged = False
 
+SIGNAL_BY_NUM = dict(
+    (getattr(signal, name), name)
+    for name in sorted(vars(signal), reverse=True)
+    if name.startswith('SIG') and not name.startswith('SIG_')
+)
+
 
 def get_log_level():
     return (LOG.level or logging.getLogger().level or logging.INFO)
@@ -584,6 +590,21 @@ def _proxy_connect(name, method_name, kwargs, econtext):
     }
 
 
+def wstatus_to_str(status):
+    """
+    Parse and format a :func:`os.waitpid` exit status.
+    """
+    if os.WIFEXITED(status):
+        return 'exited with return code %d' % (os.WEXITSTATUS(status),)
+    if os.WIFSIGNALED(status):
+        n = os.WTERMSIG(status)
+        return 'exited due to signal %d (%s)' % (n, SIGNAL_BY_NUM.get(n))
+    if os.WIFSTOPPED(status):
+        n = os.WSTOPSIG(status)
+        return 'stopped due to signal %d (%s)' % (n, SIGNAL_BY_NUM.get(n))
+    return 'unknown wait status (%d)' % (status,)
+
+
 class Argv(object):
     """
     Wrapper to defer argv formatting when debug logging is disabled.
@@ -961,7 +982,7 @@ class Stream(mitogen.core.Stream):
 
         self._reaped = True
         if pid:
-            LOG.debug('%r: child process exit status was %d', self, status)
+            LOG.debug('%r: PID %d %s', self, pid, wstatus_to_str(status))
             return
 
         # For processes like sudo we cannot actually send sudo a signal,

tests/parent_test.py

@@ -1,5 +1,6 @@
 import errno
 import os
+import signal
 import subprocess
 import sys
 import tempfile
@@ -44,6 +45,41 @@ class GetDefaultRemoteNameTest(testlib.TestCase):
         self.assertEquals("ECORP_Administrator@box:123", self.func())
 
 
+class WstatusToStrTest(testlib.TestCase):
+    func = staticmethod(mitogen.parent.wstatus_to_str)
+
+    def test_return_zero(self):
+        pid = os.fork()
+        if not pid:
+            os._exit(0)
+        (pid, status), _ = mitogen.core.io_op(os.waitpid, pid, 0)
+        self.assertEquals(self.func(status),
+                          'exited with return code 0')
+
+    def test_return_one(self):
+        pid = os.fork()
+        if not pid:
+            os._exit(1)
+        (pid, status), _ = mitogen.core.io_op(os.waitpid, pid, 0)
+        self.assertEquals(
+            self.func(status),
+            'exited with return code 1'
+        )
+
+    def test_sigkill(self):
+        pid = os.fork()
+        if not pid:
+            time.sleep(600)
+        os.kill(pid, signal.SIGKILL)
+        (pid, status), _ = mitogen.core.io_op(os.waitpid, pid, 0)
+        self.assertEquals(
+            self.func(status),
+            'exited due to signal %s (SIGKILL)' % (signal.SIGKILL,)
+        )
+
+    # can't test SIGSTOP without POSIX sessions rabbithole
+
+
 class ReapChildTest(testlib.RouterMixin, testlib.TestCase):
     def test_connect_timeout(self):
         # Ensure the child process is reaped if the connection times out.