don't use a property, instead use simple function. spotted by davisp:

"It seems too magical to me"

gunicorn/arbiter.py

@@ -15,7 +15,7 @@ import sys
 import time
 import traceback
 
-from gunicorn.pidfile import Pidfile
+from gunicorn.pidfile import set_pidfile, unlink_pidfile
 from gunicorn.sock import create_socket
 from gunicorn.workers.sync import SyncWorker
 from gunicorn import util
@@ -44,8 +44,6 @@ class Arbiter(object):
         if name[:3] == "SIG" and name[3] != "_"
     )
     
-    pidfile = Pidfile()
-
     def __init__(self, cfg, app):
         self.cfg = cfg
         self.app = app
@@ -64,7 +62,7 @@ class Arbiter(object):
             self.log.error("%s" % e)
             sys.exit(1)
         
-        self._pidfile = None
+        self.pidfile = None
         self.worker_age = 0
         self.reexec_pid = 0
         self.master_name = "Master"
@@ -94,7 +92,7 @@ class Arbiter(object):
         self.pid = os.getpid()
         self.init_signals()
         self.LISTENER = create_socket(self.cfg)
-        self.pidfile = self.cfg.pidfile
+        self.pidfile = set_pidfile(self.pid, self.cfg.pidfile, self.pidfile)
         self.log.info("Arbiter booted")
         self.log.info("Listening at: %s" % self.LISTENER)
         
@@ -155,13 +153,13 @@ class Arbiter(object):
                             traceback.format_exc())
                 self.stop(False)
                 if self.pidfile:
-                    del self.pidfile
+                    unlink_pidfile(self.pid, self.pidfile)
                 sys.exit(-1)
 
         self.stop()
         self.log.info("Shutting down: %s" % self.master_name)
         if self.pidfile:
-            del self.pidfile
+            unlink_pidfile(self.pid, self.pidfile)
         sys.exit(0)
         
     def handle_chld(self, sig, frame):
@@ -289,7 +287,7 @@ class Arbiter(object):
         """
         if self.pidfile:
             old_pidfile = "%s.oldbin" % self.pidfile
-            self.pidfile = old_pidfile            
+            self.pidfile = set_pidfile(self.pid, old_pidfile)            
         
         self.reexec_pid = os.fork()
         if self.reexec_pid != 0:

gunicorn/pidfile.py

@@ -9,65 +9,53 @@ import errno
 import os
 import tempfile
 
-class Pidfile(object):
+
+def set_pidfile(pid, path, oldpath=None):
+    oldpid = valid_pidfile(path)
+    if oldpid:
+        if oldpath is not None and path == oldpath and \
+                oldpid == os.getpid():
+            return path
+        raise RuntimeError("Already running on PID %s " \
+                    "(or pid file '%s' is stale)" % (os.getpid(), path))
+                    
+    if oldpath:    
+        unlink_pidfile(pid, path)
+
+    # write pidfile
+    fd, fname = tempfile.mkstemp(dir=os.path.dirname(path))
+    os.write(fd, "%s\n" % pid)
+    os.rename(fname, path)
+    os.close(fd)
+    return path
     
-    def __get__(self, instance, cls):
-        if instance is None:
-            return self
+def unlink_pidfile(pid, path):
+    """ delete pidfile"""
+    try:
+        with open(path, "r") as f:
+            pid1 =  int(f.read() or 0)
             
-        return instance._pidfile
-        
-    def __set__(self, instance, path):
-        if not path:
+        if pid1 == pid:
+            os.unlink(path)
+    except:
+        pass
+    
+def valid_pidfile(path):
+    """ Validate pidfile and make it stale if needed"""
+    try:
+        with open(path, "r") as f:
+            wpid = int(f.read() or 0)
+
+            if wpid <= 0: return None
+ 
+            try:
+                os.kill(wpid, 0)
+                return wpid
+            except OSError, e:
+                if e[0] == errno.ESRCH:
+                    return
+                raise
+    except IOError, e:
+        if e[0] == errno.ENOENT:
             return
-        pid = self.valid_pidfile(path)
-        if pid:
-            if instance._pidfile is not None and path == instance._pidfile and \
-                    pid == os.getpid():
-                return path
-            raise RuntimeError("Already running on PID %s " \
-                        "(or pid file '%s' is stale)" % (os.getpid(), path))
-        if instance._pidfile:    
-            self.unlink_pidfile(instance, instance._pidfile)
-
-        # write pidfile
-        fd, fname = tempfile.mkstemp(dir=os.path.dirname(path))
-        os.write(fd, "%s\n" % instance.pid)
-        os.rename(fname, path)
-        os.close(fd)
-        instance._pidfile = path
-        
-    def __delete__(self, instance):
-        self.unlink_pidfile(instance, instance._pidfile)
-        instance._pidfile = None
-        
-    def unlink_pidfile(self, instance, path):
-        """ delete pidfile"""
-        try:
-            with open(path, "r") as f:
-                pid =  int(f.read() or 0)
-                
-            if pid == instance.pid:
-                os.unlink(path)
-        except:
-            pass
-        
-    def valid_pidfile(self, path):
-        """ Validate pidfile and make it stale if needed"""
-        try:
-            with open(path, "r") as f:
-                wpid = int(f.read() or 0)
-
-                if wpid <= 0: return None
-     
-                try:
-                    os.kill(wpid, 0)
-                    return wpid
-                except OSError, e:
-                    if e[0] == errno.ESRCH:
-                        return
-                    raise
-        except IOError, e:
-            if e[0] == errno.ENOENT:
-                return
-            raise
+        raise