move daemonize support to own module

git-svn-id: https://svn.mcs.anl.gov/repos/bcfg/trunk/bcfg2@4113 ce84e21b-d406-0410-9b95-82705330c041

1 files changed, 44 insertions, 0 deletions

diff --git a/src/lib/Daemon.py b/src/lib/Daemon.py
new file mode 100644
index 000000000..1886f5569
--- /dev/null
+++ b/src/lib/Daemon.py
@@ -0,0 +1,44 @@
+'''Bcfg2 daemon support'''
+__revision__ = '$Revision'
+
+import os, sys
+
+def daemonize(filename):
+    '''Do the double fork/setsession dance'''
+    # Check if the pid is active
+    try:
+        pidfile = open(filename, "r")
+        oldpid = int(pidfile.readline())
+        # getpgid() will retun an IO error if all fails
+        os.getpgid(oldpid)
+        pidfile.close()
+
+        # If we got this far without exceptions, there is another instance
+        # running. Exit gracefully.
+        print "PID File (%s) exists and listed PID (%d) is active." % \
+              (filename, oldpid)
+        raise SystemExit, 1
+    except OSError:
+        pidfile.close()
+    except IOError: 
+        # pid file doesn't
+        pass
+
+    # Fork once
+    if os.fork() != 0:      
+        os._exit(0)         
+    os.setsid()                     # Create new session
+    pid = os.fork()
+    if pid != 0:
+        pidfile = open(filename, "w")
+        pidfile.write("%i" % pid)
+        pidfile.close()
+        os._exit(0)     
+    os.chdir("/")         
+    os.umask(0)
+
+    null = open("/dev/null", "w+")
+
+    os.dup2(null.fileno(), sys.__stdin__.fileno())
+    os.dup2(null.fileno(), sys.__stdout__.fileno())
+    os.dup2(null.fileno(), sys.__stderr__.fileno())