Enable stdio inheritance.

Enable inheritance for stdio file descriptors in daemon mode. It allows
you in daemon mode to redirect the output to a file if needed.

By default in daemon mode gunicorn will close all file handle except if
you pass the "-R" options. In this cases STDIO will be preserved.

fix #309

gunicorn/app/base.py

@@ -119,8 +119,9 @@ class Application(object):
 
         if self.cfg.spew:
             debug.spew()
+
         if self.cfg.daemon:
-            util.daemonize()
+            util.daemonize(self.cfg.enable_stdio_inheritance)
 
         # set python paths
         if self.cfg.pythonpath and self.cfg.pythonpath is not None:

gunicorn/config.py

@@ -1292,3 +1292,17 @@ class SyslogFacility(Setting):
     desc = """\
     Syslog facility name
     """
+
+
+class EnableStdioInheritance(Setting):
+    name = "enable_stdio_inheritance"
+    section = "Logging"
+    cli = ["-R", "--enable-stdio-inheritance"]
+    validator = validate_bool
+    default = False
+    action = "store_true"
+    desc = """\
+    Enable stdio inheritance
+
+    Enable inheritance for stdio file descriptors in daemon mode.
+    """

gunicorn/util.py

@@ -403,7 +403,15 @@ def is_hoppish(header):
     return header.lower().strip() in hop_headers
 
 
-def daemonize():
+def disable_stdout_buffering():
+    _old_write = sys.stdout.write
+    def _write(*args, **kwargs):
+        _old_write(*args, **kwargs)
+        sys.stdout.flush()
+
+    sys.stdout.write = _write
+
+def daemonize(enable_stdio_inheritance=False):
     """\
     Standard daemonization of a process.
     http://www.svbug.com/documentation/comp.unix.programmer-FAQ/faq_2.html#SEC16
@@ -417,13 +425,27 @@ def daemonize():
             os._exit(0)
 
         os.umask(0)
+
         maxfd = get_maxfd()
-        closerange(0, maxfd)
-
-        os.open(REDIRECT_TO, os.O_RDWR)
-        os.dup2(0, 1)
-        os.dup2(0, 2)
+        if not enable_stdio_inheritance:
+            closerange(0, maxfd)
 
+            os.open(REDIRECT_TO, os.O_RDWR)
+            os.dup2(0, 1)
+            os.dup2(0, 2)
+        else:
+            closerange(3, maxfd)
+            os.open(REDIRECT_TO, os.O_RDWR)
+            for stream in (sys.stdin, sys.stdout, sys.stderr):
+                fd = stream.fileno()
+                try:
+                    if stream.isatty():
+                        os.close(fd)
+                        if fd in (1, 2):
+                            os.dup2(0, fd)
+                except AttributeError:
+                    pass
+            disable_stdout_buffering()
 
 def seed():
     try: