A computationally intensive process run from the command line works fine, runs to completion after several minutes, writing a few hundred lines of text to standard output and creating, writing to and closing around 200 files of size around 20KB.

Now run from std.process.pipeProcess and periodically tested for completion with tryWait interleaved with sleep everything seems fine for a while. htop reveals that one core is running this at 100% CPU, and the first 76 files appear one after another, but the 77th file is opened and nothing is written to it, and htop reveals that the CPU usage has dropped to zero, and yet the process is still running according to ps, and this continues indefinitely, no error message, no indication from tryWait that it is done. htop does not reveal at any point that memory use is even half of what is available.

Previously with similar processes that are a somewhat scaled back version of the one that fails as above, there's been no difference between what happened at the command line and what's happening here.

Any ideas or suggestions?

On Friday, 1 June 2018 at 13:40:51 UTC, Carl Sturtivant wrote:
> A computationally intensive process run from the command line works fine, runs to completion after several minutes, writing a few hundred lines of text to standard output and creating, writing to and closing around 200 files of size around 20KB.
>
> Now run from std.process.pipeProcess and periodically tested for completion with tryWait interleaved with sleep everything seems fine for a while. htop reveals that one core is running this at 100% CPU, and the first 76 files appear one after another, but the 77th file is opened and nothing is written to it, and htop reveals that the CPU usage has dropped to zero, and yet the process is still running according to ps, and this continues indefinitely, no error message, no indication from tryWait that it is done. htop does not reveal at any point that memory use is even half of what is available.
>
> Previously with similar processes that are a somewhat scaled back version of the one that fails as above, there's been no difference between what happened at the command line and what's happening here.
>
> Any ideas or suggestions?

1/ Maybe something with stdin

I don't believe this is the issue but if one proc expects input and if its stdin is not closed then it'll stuck in the code where input is read. E.g maybe something like

    ProcessPipes pp = pipeProcess(...);
    pp.stdin.close;

is needed somewhere ?

2/ Maybe something with stdout

If not all the output is read then the proc doesn't finish.
So something like this is needed maybe ?

    ProcessPipes pp = pipeProcess(...);
    foreach(c; pp.stdout.byChunk(4096)) {...}


These are blind ideas.
It would better if you can show some code.

On 6/1/18 9:40 AM, Carl Sturtivant wrote:
> A computationally intensive process run from the command line works fine, runs to completion after several minutes, writing a few hundred lines of text to standard output and creating, writing to and closing around 200 files of size around 20KB.
> 
> Now run from std.process.pipeProcess and periodically tested for completion with tryWait interleaved with sleep everything seems fine for a while. htop reveals that one core is running this at 100% CPU, and the first 76 files appear one after another, but the 77th file is opened and nothing is written to it, and htop reveals that the CPU usage has dropped to zero, and yet the process is still running according to ps, and this continues indefinitely, no error message, no indication from tryWait that it is done. htop does not reveal at any point that memory use is even half of what is available.
> 
> Previously with similar processes that are a somewhat scaled back version of the one that fails as above, there's been no difference between what happened at the command line and what's happening here.
> 
> Any ideas or suggestions?

Are the sub-processes outputting anything? Because that is what can cause issues like this -- you have to process the pipe output or else it stalls when the pipe buffer gets full. It seems like you aren't processing the output from your description, but hard to tell without more context.

-Steve