process_wrap/std/
job_object.rs

1use std::{
2	io::Result,
3	os::windows::{io::AsRawHandle, process::CommandExt},
4	process::{Child, Command, ExitStatus},
5	time::Duration,
6};
7
8#[cfg(feature = "tracing")]
9use tracing::{debug, instrument};
10use windows::Win32::{
11	Foundation::{CloseHandle, HANDLE},
12	System::Threading::CREATE_SUSPENDED,
13};
14
15use crate::{
16	windows::{make_job_object, resume_threads, terminate_job, wait_on_job, JobPort},
17	ChildExitStatus,
18};
19
20#[cfg(feature = "creation-flags")]
21use super::CreationFlags;
22use super::{StdChildWrapper, StdCommandWrap, StdCommandWrapper};
23
24/// Wrapper which creates a job object context for a `Command`.
25///
26/// This wrapper is only available on Windows.
27///
28/// It creates a Windows Job Object and associates the [`Command`] to it. This behaves analogously
29/// to process groups on Unix or even cgroups on Linux, with the ability to restrict resource use.
30/// See [Job Objects](https://docs.microsoft.com/en-us/windows/win32/procthread/job-objects).
31///
32/// This wrapper provides a child wrapper: [`JobObjectChild`].
33#[derive(Clone, Copy, Debug)]
34pub struct JobObject;
35
36impl StdCommandWrapper for JobObject {
37	#[cfg_attr(feature = "tracing", instrument(level = "debug", skip(self)))]
38	fn pre_spawn(&mut self, command: &mut Command, core: &StdCommandWrap) -> Result<()> {
39		let mut flags = CREATE_SUSPENDED;
40		#[cfg(feature = "creation-flags")]
41		if let Some(CreationFlags(user_flags)) = core.get_wrap::<CreationFlags>() {
42			flags |= *user_flags;
43		}
44
45		command.creation_flags(flags.0);
46		Ok(())
47	}
48
49	#[cfg_attr(feature = "tracing", instrument(level = "debug", skip(self)))]
50	fn wrap_child(
51		&mut self,
52		inner: Box<dyn StdChildWrapper>,
53		core: &StdCommandWrap,
54	) -> Result<Box<dyn StdChildWrapper>> {
55		#[cfg(feature = "creation-flags")]
56		let create_suspended = core
57			.get_wrap::<CreationFlags>()
58			.map_or(false, |flags| flags.0.contains(CREATE_SUSPENDED));
59		#[cfg(not(feature = "creation-flags"))]
60		let create_suspended = false;
61
62		debug!(?create_suspended, "options from other wrappers");
63
64		let handle = HANDLE(inner.inner().as_raw_handle() as _);
65
66		let job_port = make_job_object(handle, false)?;
67
68		// only resume if the user didn't specify CREATE_SUSPENDED
69		if !create_suspended {
70			resume_threads(handle)?;
71		}
72
73		Ok(Box::new(JobObjectChild::new(inner, job_port)))
74	}
75}
76
77/// Wrapper for `Child` which waits on all processes within the job.
78#[derive(Debug)]
79pub struct JobObjectChild {
80	inner: Box<dyn StdChildWrapper>,
81	exit_status: ChildExitStatus,
82	job_port: JobPort,
83}
84
85impl JobObjectChild {
86	#[cfg_attr(feature = "tracing", instrument(level = "debug", skip(job_port)))]
87	pub(crate) fn new(inner: Box<dyn StdChildWrapper>, job_port: JobPort) -> Self {
88		Self {
89			inner,
90			exit_status: ChildExitStatus::Running,
91			job_port,
92		}
93	}
94}
95
96impl StdChildWrapper for JobObjectChild {
97	fn inner(&self) -> &Child {
98		self.inner.inner()
99	}
100	fn inner_mut(&mut self) -> &mut Child {
101		self.inner.inner_mut()
102	}
103	fn into_inner(self: Box<Self>) -> Child {
104		// manually drop the completion port
105		let its = std::mem::ManuallyDrop::new(self.job_port);
106		unsafe { CloseHandle(its.completion_port.0) }.ok();
107		// we leave the job handle unclosed, otherwise the Child is useless
108		// (as closing it will terminate the job)
109
110		self.inner.into_inner()
111	}
112
113	#[cfg_attr(feature = "tracing", instrument(level = "debug", skip(self)))]
114	fn start_kill(&mut self) -> Result<()> {
115		terminate_job(self.job_port.job, 1)
116	}
117
118	#[cfg_attr(feature = "tracing", instrument(level = "debug", skip(self)))]
119	fn wait(&mut self) -> Result<ExitStatus> {
120		if let ChildExitStatus::Exited(status) = &self.exit_status {
121			return Ok(*status);
122		}
123
124		// always wait for parent to exit first, as by the time it does,
125		// it's likely that all its children have already exited.
126		let status = self.inner.wait()?;
127		self.exit_status = ChildExitStatus::Exited(status);
128
129		// nevertheless, now wait and make sure we reap all children.
130		let JobPort {
131			completion_port, ..
132		} = self.job_port;
133		wait_on_job(completion_port, None)?;
134		Ok(status)
135	}
136
137	#[cfg_attr(feature = "tracing", instrument(level = "debug", skip(self)))]
138	fn try_wait(&mut self) -> Result<Option<ExitStatus>> {
139		wait_on_job(self.job_port.completion_port, Some(Duration::ZERO))?;
140		self.inner.try_wait()
141	}
142}
process_wrap/std/job_object.rs

process_wrap/std/
job_object.rs
