Negative feedback for bad headers. Purge cache logs on startup.

Milter/plock.py

@@ -0,0 +1,62 @@
+# Author: Stuart D. Gathman <stuart@bmsi.com>
+# Copyright 2001 Business Management Systems, Inc.
+# This code is under the GNU General Public License.  See COPYING for details.
+
+import os
+from time import sleep
+
+class PLock(object):
+  "A simple /etc/passwd style lock,update,rename protocol for updating files."
+  def __init__(self,basename):
+    self.basename = basename
+    self.fp = None
+
+  def lock(self,lockname=None):
+    "Start an update transaction.  Return FILE to write new version."
+    self.unlock()
+    if not lockname:
+      lockname = self.basename + '.lock'
+    self.lockname = lockname
+    st = os.stat(self.basename)
+    u = os.umask(0002)
+    try:
+      fd = os.open(lockname,os.O_WRONLY+os.O_CREAT+os.O_EXCL,st.st_mode|0660)
+    finally:
+      os.umask(u)
+    self.fp = os.fdopen(fd,'w')
+    try:
+      os.chown(self.lockname,-1,st.st_gid)
+    except:
+      self.unlock()
+      raise
+    return self.fp
+
+  def wlock(self,lockname=None):
+    "Wait until lock is free, then start an update transaction."
+    while True:
+      try:
+        return self.lock(lockname)
+      except OSError:
+        sleep(2)
+
+  def commit(self,backname=None):
+    "Commit update transaction with optional backup file."
+    if not self.fp:
+      raise IOError,"File not locked"
+    self.fp.close()
+    self.fp = None
+    if backname:
+      try:
+	os.remove(backname)
+      except OSError: pass
+      os.link(self.basename,backname)
+    os.rename(self.lockname,self.basename)
+
+  def unlock(self):
+    "Cancel update transaction."
+    if self.fp:
+      try:
+        self.fp.close()
+      except: pass
+      self.fp = None
+      os.remove(self.lockname)