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I would like to find a Ubuntu Linux 16.04 systen command similar to strace to find out why my C++ program , ServiceController.exe , which 

[execle  ("/usr/lib/mono/4.5/mono-service","/usr/lib/mono/4.5/mono-service",
         "./Debug/ComputationalImageClientServer.exe", 
          0, char const* EnvironmentPtr)]

mysteriously stop running after 90 seconds * where * ComputationalImageClientServer.exe and ComputatationalImageClientServer.exe are C#/.NET 4.5 executables

In contrast, when I run /usr/lib/mono/4.5/mono-service.exe  ./Debug/ComputatationalImageVideoServer.exe" at the command prompt,

it runs continually for 24 hours by 7 days at least.

Why cannot the first example run continuously 24X7? How might I diagnose, debug and fix this error?

open("Delaware_Client_Server.exe", O_RDONLY) = 3
pipe2([4, 5], O_CLOEXEC)                = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f743e4dca10) = 3509
close(5)                                = 0
fcntl(4, F_SETFD, 0)                    = 0
fstat(4, {st_mode=S_IFIFO|0600, st_size=0, ...}) = 0
read(4, "", 4096)                       = 0
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=3509, si_uid=1000, si_status=1, si_utime=0, si_stime=0} ---
close(4)                                = 0
wait4(3509, [{WIFEXITED(s) && WEXITSTATUS(s) == 1}], 0, NULL) = 3509
write(1, "\n", 1)                       = 1
write(1, "Process returned 256\n", 21)  = 21
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  • Is there a difference between 24x7 and continuous that I am not aware of?
    – Anthon
    May 28, 2016 at 11:26
  • @Anthon, Thank you for your comment and nice edit. There is no difference between 24x7 and continuous for us. I am curious to find out why my C++ program , ServiceController.exe , which [execle ("/usr/lib/mono/4.5/monoservice", "/usr/lib/mono/4.5/mono-service", "./Debug/ComputationalImageClientServer.exe", 0, char const* Envp)] mysteriously stops running after 90 seconds.
    – Frank
    May 28, 2016 at 14:15
  • @Anthon, I forget to say that the executable , "./Debug/ComputationalImageClientServer.exe", is a C#/.NET 4.5 which reads and writes a MySQL database. Thank you,
    – Frank
    May 28, 2016 at 14:23
  • Try out strace first. Maybe it dies due to signal.
    – user140866
    May 28, 2016 at 15:45
  • @siblynx, Thank you for your message. What signals could cause it to die?
    – Frank
    May 29, 2016 at 1:14

2 Answers 2

Reset to default
2

Use the GNU debugger, gdb, or something similar.

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  • @ojs, Thank you for your answer. How could gdb inspect a C# program? I know that Monodevelop can debug C# programs if attached properly which I do not know how to do in this case.
    – Frank
    May 28, 2016 at 14:26
  • Sorry, but I can't be any more specific on my answer. I don't know that much about Mono. Perhaps asking in stackoverflow would be more appropriate since this is kind of a programming question. But I think you have to get a debugger to solve this.
    – ojs
    May 28, 2016 at 14:50
0

What's the difference between running a program as a daemon and forking it into background with '&'?

states that perhaps SIGHUP is the culprit signal which causes ServiceController.exe to stop running after 90 seconds. nohup command & prevents this from happening.

With command & Your process will be killed by a SIGHUP signal when the parent dies.

Sysadmins have access to some workarounds, though.

On a bash system, you can use: (trap '' HUP; command) &

This opens a subshell, traps the HUP signal with an empty handler and ampersand/forks it.

Output might still get redirected to the wrong tty. Or get lost. You may fix that with &>command.out, 1>output.out, or 2>errors.out

You might also have access, on most systems, to the nohup command. nohup simplifies this process greatly. It's quite standard, but I found many busybox embedded ARM distributions missing it. You just write: nohup command &

..and you're done. Output gets redirected, IIRC, to nohup.out, but this filename can be changed with an option.

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11
  • @siblynx, Could you look at this answer and see if it is plausible? Thank you.
    – Frank
    May 30, 2016 at 7:13
  • On my systems I do not care and, if I do not need any output from process I just force it go daemon mode. I dislike & shell operand because process spawned this way still have controlling tty and other attributes which I usually do not need at all. If I need output from process, I just spawn a subshell in a fork sh -c 'cmds &>out.log' way. And my processes do not get HUPed because they are already lose their ttys and obtain only raw IO fds allocated by shell or fork. fork.c
    – user140866
    May 31, 2016 at 13:28
  • Now about SIGCHLD. If your process receives this then there is a reason to. But, if you really cannot change the situation (you have no source code for the program you running?), maybe you will try this program to forcibly ignore signals? How about sigign? sigign.c You specify numeric values of signals to ignore and then specify cmdline to run with ignored signals. See sigign.README
    – user140866
    May 31, 2016 at 13:36
  • But I still think you should try to see what changes are there after 90s timeout when your process receives CHLD. Specifically what process did exited or what else raised CHLD signal.
    – user140866
    May 31, 2016 at 13:47
  • @siblynx, I just added the strace output at the bottom of the original question for everyone to see. Evidently SIGCHLD is not being masked. Thank you.
    – Frank
    May 31, 2016 at 14:21

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