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2a0e09842e
For some reason that I was unable to determine, trying to cover
the case failure to fork during the second fork causes an error
when running the testsuite with coverage, such as:
$ ./coverage.sh -j16 --enable-color tests/LC28-010__daemon_utest
We get a crash during the execution of the at_exit handling when
the coverage framework tries to create a file in the root ("/")
directory, presumably to save the coverage information. I couldn't
figure out why this was happening, nor could I find a fix. Since
the code we're trying is not expected to change much over time,
and the second fork error handling is only about damage control,
I gave up on the idea. Instead, I commented out the corresponding
testing code, so as for it to be available should we try to solve
that mystery again, and I added a "pragma nocover" in run_in_daemon.
This had the side-effect of dropping one call to syslog that was
contributing to full coverage. This commit simply extends the unit
test to include a call to that function as well.
TN: U627-007
Change-Id: Iaacfd174747ff43a921f5d17e3a74900ad96a78e
98 lines
2.7 KiB
Python
98 lines
2.7 KiB
Python
"""A module to handle daemonization...
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"""
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from __future__ import print_function
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import os
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import sys
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from syslog import syslog
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def daemonize(output_fd=None):
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"""Create a daemon process.
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PARAMETERS
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output_fd: If not none, a file descriptor where stdout and
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stderr should be redirected.
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RETURN VALUE
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This function returns True for the child (daemon) process,
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while it returns False for the parent process.
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"""
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# Flush the output a first time to make sure the child processes
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# do not inherit some buffered output from the parent, causing
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# some output generated by the parent to be printed multiple times
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# due to both parent and child printing it at flush time.
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for f in sys.stdout, sys.stderr:
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f.flush()
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# Perform the first fork.
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try:
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pid = os.fork()
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if pid > 0:
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# In the parent. We can now return.
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return False
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except OSError as e:
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sys.stderr.write("fork #1 failed: (%d) %s\n" % (e.errno, e.strerror))
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return False
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# Decouple ourselves from the parent environment.
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os.chdir("/")
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os.umask(0)
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os.setsid()
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# Perform the second fork, to daemonize ourselves.
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try:
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pid = os.fork()
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if pid > 0:
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# In the second parent. Exit.
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sys.exit(0)
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except OSError as e: # pragma: no cover (really hard to cover -- see U627-007)
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syslog("git-hooks: fork #2 failed: (%d) %s" % (e.errno, e.strerror))
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sys.exit(1)
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# Flush the output...
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for f in sys.stdout, sys.stderr:
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f.flush()
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# Perform the input/output redirection.
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os.close(0)
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os.dup2(os.open("/dev/null", os.O_RDONLY), 0)
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if output_fd is None: # pragma: no cover (never true in testsuite mode)
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output_fd = os.open("/dev/null", os.O_WRONLY)
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os.close(1)
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os.dup2(output_fd, 1)
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os.close(2)
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os.dup2(output_fd, 2)
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return True
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def run_in_daemon(fun):
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"""Run the given callbable in a daemon process.
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In GIT_HOOKS_TESTSUITE_MODE, the function's stdout and stderr
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is redirected to a pipe and then re-printed on our stdout.
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But this is only for testing purposes. In normal mode,
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the function's stdout/stderr, as well as stdin are redirected
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to /dev/null.
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PARAMETERS
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fun: A callable.
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"""
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daemon_pipe = (None, None)
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if "GIT_HOOKS_TESTSUITE_MODE" in os.environ:
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daemon_pipe = os.pipe()
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in_daemon = daemonize(daemon_pipe[1])
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if in_daemon:
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fun()
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sys.exit(0)
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else:
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if daemon_pipe[0] is not None:
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os.close(daemon_pipe[1])
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daemon_stdout = os.fdopen(daemon_pipe[0])
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print(daemon_stdout.read(), file=sys.stderr, end="")
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daemon_stdout.close()
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