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digitalmars.D - Avoid zombie processes with std.process

reply FreeSlave <freeslave93 gmail.com> writes:
Are there plans on adding something like spawnProcessDetached 
that would start processes completely independent from parent? 
I.e. in other process group and, what is important, with no need 
for wait.

On Posix that could be done via double fork technique. Not sure 
about Windows.
Aug 24 2016
next sibling parent reply eugene <egordeev18 gmail.com> writes:
On Wednesday, 24 August 2016 at 11:04:58 UTC, FreeSlave wrote:

 Are there plans on adding something like spawnProcessDetached 
 that would start processes completely independent from parent? 
 I.e. in other process group and, what is important, with no 
 need for wait.

 On Posix that could be done via double fork technique. Not sure 
 about Windows.


could you give some use-cases and list drawbacks of that addition?
Aug 24 2016
next sibling parent FreeSlave <freeslave93 gmail.com> writes:
On Wednesday, 24 August 2016 at 15:48:24 UTC, eugene wrote:

 On Wednesday, 24 August 2016 at 11:04:58 UTC, FreeSlave wrote:

 Are there plans on adding something like spawnProcessDetached 
 that would start processes completely independent from parent? 
 I.e. in other process group and, what is important, with no 
 need for wait.

 On Posix that could be done via double fork technique. Not 
 sure about Windows.


 could you give some use-cases and list drawbacks of that 
 addition?


Use case: e.g. launch application from file manager. File manager 
may not care about waiting for applications to exit.

Drawbacks: why there should be one?
Aug 25 2016
prev sibling parent Brian <zoujiaqing gmail.com> writes:
On Wednesday, 24 August 2016 at 15:48:24 UTC, eugene wrote:

 On Wednesday, 24 August 2016 at 11:04:58 UTC, FreeSlave wrote:

 Are there plans on adding something like spawnProcessDetached 
 that would start processes completely independent from parent? 
 I.e. in other process group and, what is important, with no 
 need for wait.

 On Posix that could be done via double fork technique. Not 
 sure about Windows.


 could you give some use-cases and list drawbacks of that 
 addition?


collie ( https://github.com/putaolabs/collie ):
An asynchronous event-driven network framework written in D.
I'm sure you will like it :)
Sep 22 2016
prev sibling next sibling parent Basile B. <b2.temp gmx.com> writes:
On Wednesday, 24 August 2016 at 11:04:58 UTC, FreeSlave wrote:

 Are there plans on adding something like spawnProcessDetached 
 that would start processes completely independent from parent? 
 I.e. in other process group and, what is important, with no 
 need for wait.

 On Posix that could be done via double fork technique. Not sure 
 about Windows.


An async process is what you want.None of the D async frameworks 
implement this. They'are all focused on network, like if it's 
easyer to test /:

https://github.com/putaolabs/collie
https://github.com/dcarp/asynchronous
https://github.com/etcimon/libasync
Aug 24 2016
prev sibling parent reply Shachar Shemesh <shachar weka.io> writes:
On 24/08/16 14:04, FreeSlave wrote:

 Are there plans on adding something like spawnProcessDetached that would
 start processes completely independent from parent? I.e. in other
 process group and, what is important, with no need for wait.

 On Posix that could be done via double fork technique. Not sure about
 Windows.


Double fork on Posix is, usually, used for something slightly different. 
In particular, since you bring up the process group, I think you mean 
daemonization.

Daemonization, however, does a bit more than create a new process group 
and double forking.

http://forum.dlang.org/thread/d83ugn$265f$1 digitaldaemon.com has 
discussion and some code regarding this issue.

Shachar
Aug 25 2016
parent reply FreeSlave <freeslave93 gmail.com> writes:
On Thursday, 25 August 2016 at 07:32:29 UTC, Shachar Shemesh 
wrote:

 On 24/08/16 14:04, FreeSlave wrote:

 Are there plans on adding something like spawnProcessDetached 
 that would
 start processes completely independent from parent? I.e. in 
 other
 process group and, what is important, with no need for wait.

 On Posix that could be done via double fork technique. Not 
 sure about
 Windows.


 Double fork on Posix is, usually, used for something slightly 
 different. In particular, since you bring up the process group, 
 I think you mean daemonization.

 Daemonization, however, does a bit more than create a new 
 process group and double forking.

 http://forum.dlang.org/thread/d83ugn$265f$1 digitaldaemon.com 
 has discussion and some code regarding this issue.

 Shachar


It's not about daemonization only. Different process group is 
needed to prevent signal distribution. Again, e.g. file manager 
and launched application may want to not be connected in any way.
Aug 25 2016
parent reply Shachar Shemesh <shachar weka.io> writes:
On 25/08/16 11:46, FreeSlave wrote:

 On Thursday, 25 August 2016 at 07:32:29 UTC, Shachar Shemesh wrote:

 On 24/08/16 14:04, FreeSlave wrote:

 Are there plans on adding something like spawnProcessDetached that would
 start processes completely independent from parent? I.e. in other
 process group and, what is important, with no need for wait.

 On Posix that could be done via double fork technique. Not sure about
 Windows.


 Double fork on Posix is, usually, used for something slightly
 different. In particular, since you bring up the process group, I
 think you mean daemonization.

 Daemonization, however, does a bit more than create a new process
 group and double forking.

 http://forum.dlang.org/thread/d83ugn$265f$1 digitaldaemon.com has
 discussion and some code regarding this issue.

 Shachar


 It's not about daemonization only. Different process group is needed to
 prevent signal distribution. Again, e.g. file manager and launched
 application may want to not be connected in any way.


Yes, that's part of daemonization. So is chdir somewhere else and 
closing all open file descriptors, including stdin/out/err.

http://0pointer.de/public/systemd-man/daemon.html#SysV%20Daemons
Aug 25 2016
parent FreeSlave <freeslave93 gmail.com> writes:
On Thursday, 25 August 2016 at 14:53:30 UTC, Shachar Shemesh 
wrote:

 On 25/08/16 11:46, FreeSlave wrote:

 On Thursday, 25 August 2016 at 07:32:29 UTC, Shachar Shemesh 
 wrote:

 On 24/08/16 14:04, FreeSlave wrote:

 Are there plans on adding something like 
 spawnProcessDetached that would
 start processes completely independent from parent? I.e. in 
 other
 process group and, what is important, with no need for wait.

 On Posix that could be done via double fork technique. Not 
 sure about
 Windows.


 Double fork on Posix is, usually, used for something slightly
 different. In particular, since you bring up the process 
 group, I
 think you mean daemonization.

 Daemonization, however, does a bit more than create a new 
 process
 group and double forking.

 http://forum.dlang.org/thread/d83ugn$265f$1 digitaldaemon.com 
 has
 discussion and some code regarding this issue.

 Shachar


 It's not about daemonization only. Different process group is 
 needed to
 prevent signal distribution. Again, e.g. file manager and 
 launched
 application may want to not be connected in any way.


 Yes, that's part of daemonization. So is chdir somewhere else 
 and closing all open file descriptors, including stdin/out/err.

 http://0pointer.de/public/systemd-man/daemon.html#SysV%20Daemons


It's part of daemonization, but again, I'm not talking 
specifically about daemons. I'm talking about spawning of 
detached process (you may think about it as daemonization, but 
with less/different requirements)

Of course chdir and file descriptors should be configurable.

E.g. file managers usually set working directory of process to 
the path of executable.

When launching usual applications it's better to not close 
standard file descriptors, but redirect them to /dev/null, since 
real closing may break some apps.

Currently spawnProcess allows to set working directory and fds, 
but it implies you call wait afterwards. It would be cool if 
standard library provided the way to spawn process without 
worrying about zombies. And yes, with enough options it could 
provide support for full daemonization too (i.e. including 
closing standard fds).
Aug 25 2016