From 796345558a3a17408be2812ff0432be4ee6fe3e8 Mon Sep 17 00:00:00 2001
From: Iustin Pop <iustin@google.com>
Date: Tue, 5 Oct 2010 13:36:45 +0200
Subject: [PATCH] Abstract daemon file descriptor setup
This does some slight changes:
- Daemonize() doesn't explicitly close the file-descriptors anymore, but
only implicitly via the usage of dup2
- StartDaemonChild uses separate devnull for stdin (rdonly) and
stdout/stderr (wronly), or if using a log file, it uses it in append
mode
Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>
---
lib/utils.py | 63 ++++++++++++++++++++++++++++------------------------
1 file changed, 34 insertions(+), 29 deletions(-)
diff --git a/lib/utils.py b/lib/utils.py
index 3a6d67a72..85ea39344 100644
--- a/lib/utils.py
+++ b/lib/utils.py
@@ -252,6 +252,38 @@ def SetupDaemonEnv(cwd="/", umask=077):
os.setsid()
+def SetupDaemonFDs(output_file, output_fd):
+ """Setups up a daemon's file descriptors.
+
+ @param output_file: if not None, the file to which to redirect
+ stdout/stderr
+ @param output_fd: if not None, the file descriptor for stdout/stderr
+
+ """
+ # check that at most one is defined
+ assert [output_file, output_fd].count(None) >= 1
+
+ # Open /dev/null (read-only, only for stdin)
+ devnull_fd = os.open(os.devnull, os.O_RDONLY)
+
+ if output_fd is not None:
+ pass
+ elif output_file is not None:
+ # Open output file
+ try:
+ output_fd = os.open(output_file,
+ os.O_WRONLY | os.O_CREAT | os.O_APPEND, 0600)
+ except EnvironmentError, err:
+ raise Exception("Opening output file failed: %s" % err)
+ else:
+ output_fd = os.open(os.devnull, os.O_WRONLY)
+
+ # Redirect standard I/O
+ os.dup2(devnull_fd, 0)
+ os.dup2(output_fd, 1)
+ os.dup2(output_fd, 2)
+
+
def StartDaemon(cmd, env=None, cwd="/", output=None, output_fd=None,
pidfile=None):
"""Start a daemon process after forking twice.
@@ -398,27 +430,7 @@ def _StartDaemonChild(errpipe_read, errpipe_write,
else:
fd_pidfile = None
- # Open /dev/null
- fd_devnull = os.open(os.devnull, os.O_RDWR)
-
- assert not output or (bool(output) ^ (fd_output is not None))
-
- if fd_output is not None:
- pass
- elif output:
- # Open output file
- try:
- # TODO: Implement flag to set append=yes/no
- fd_output = os.open(output, os.O_WRONLY | os.O_CREAT, 0600)
- except EnvironmentError, err:
- raise Exception("Opening output file failed: %s" % err)
- else:
- fd_output = fd_devnull
-
- # Redirect standard I/O
- os.dup2(fd_devnull, 0)
- os.dup2(fd_output, 1)
- os.dup2(fd_output, 2)
+ SetupDaemonFDs(output, fd_output)
# Send daemon PID to parent
RetryOnSignal(os.write, pidpipe_write, str(os.getpid()))
@@ -2162,14 +2174,7 @@ def Daemonize(logfile):
else:
os._exit(0) # Exit parent of the first child.
- for fd in range(3):
- _CloseFDNoErr(fd)
- i = os.open("/dev/null", os.O_RDONLY) # stdin
- assert i == 0, "Can't close/reopen stdin"
- i = os.open(logfile, os.O_WRONLY|os.O_CREAT|os.O_APPEND, 0600) # stdout
- assert i == 1, "Can't close/reopen stdout"
- # Duplicate standard output to standard error.
- os.dup2(1, 2)
+ SetupDaemonFDs(logfile, None)
return 0
--
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