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///
34/// When both [`CreationFlags`] and [`JobObject`] are used together, [`CreationFlags`] must come first.
35#[derive(Clone, Copy, Debug)]
36pub struct JobObject;
37
38impl StdCommandWrapper for JobObject {
39	#[cfg_attr(feature = "tracing", instrument(level = "debug", skip(self)))]
40	fn pre_spawn(&mut self, command: &mut Command, core: &StdCommandWrap) -> Result<()> {
41		let mut flags = CREATE_SUSPENDED;
42		#[cfg(feature = "creation-flags")]
43		if let Some(CreationFlags(user_flags)) = core.get_wrap::<CreationFlags>() {
44			flags |= *user_flags;
45		}
46
47		command.creation_flags(flags.0);
48		Ok(())
49	}
50
51	#[cfg_attr(feature = "tracing", instrument(level = "debug", skip(self)))]
52	fn wrap_child(
53		&mut self,
54		inner: Box<dyn StdChildWrapper>,
55		core: &StdCommandWrap,
56	) -> Result<Box<dyn StdChildWrapper>> {
57		#[cfg(feature = "creation-flags")]
58		let create_suspended = core
59			.get_wrap::<CreationFlags>()
60			.map_or(false, |flags| flags.0.contains(CREATE_SUSPENDED));
61		#[cfg(not(feature = "creation-flags"))]
62		let create_suspended = false;
63
64		debug!(?create_suspended, "options from other wrappers");
65
66		let handle = HANDLE(inner.inner().as_raw_handle() as _);
67
68		let job_port = make_job_object(handle, false)?;
69
70		// only resume if the user didn't specify CREATE_SUSPENDED
71		if !create_suspended {
72			resume_threads(handle)?;
73		}
74
75		Ok(Box::new(JobObjectChild::new(inner, job_port)))
76	}
77}
78
79/// Wrapper for `Child` which waits on all processes within the job.
80#[derive(Debug)]
81pub struct JobObjectChild {
82	inner: Box<dyn StdChildWrapper>,
83	exit_status: ChildExitStatus,
84	job_port: JobPort,
85}
86
87impl JobObjectChild {
88	#[cfg_attr(feature = "tracing", instrument(level = "debug", skip(job_port)))]
89	pub(crate) fn new(inner: Box<dyn StdChildWrapper>, job_port: JobPort) -> Self {
90		Self {
91			inner,
92			exit_status: ChildExitStatus::Running,
93			job_port,
94		}
95	}
96}
97
98impl StdChildWrapper for JobObjectChild {
99	fn inner(&self) -> &Child {
100		self.inner.inner()
101	}
102	fn inner_mut(&mut self) -> &mut Child {
103		self.inner.inner_mut()
104	}
105	fn into_inner(self: Box<Self>) -> Child {
106		// manually drop the completion port
107		let its = std::mem::ManuallyDrop::new(self.job_port);
108		unsafe { CloseHandle(its.completion_port.0) }.ok();
109		// we leave the job handle unclosed, otherwise the Child is useless
110		// (as closing it will terminate the job)
111
112		self.inner.into_inner()
113	}
114
115	#[cfg_attr(feature = "tracing", instrument(level = "debug", skip(self)))]
116	fn start_kill(&mut self) -> Result<()> {
117		terminate_job(self.job_port.job, 1)
118	}
119
120	#[cfg_attr(feature = "tracing", instrument(level = "debug", skip(self)))]
121	fn wait(&mut self) -> Result<ExitStatus> {
122		if let ChildExitStatus::Exited(status) = &self.exit_status {
123			return Ok(*status);
124		}
125
126		// always wait for parent to exit first, as by the time it does,
127		// it's likely that all its children have already exited.
128		let status = self.inner.wait()?;
129		self.exit_status = ChildExitStatus::Exited(status);
130
131		// nevertheless, now wait and make sure we reap all children.
132		let JobPort {
133			completion_port, ..
134		} = self.job_port;
135		wait_on_job(completion_port, None)?;
136		Ok(status)
137	}
138
139	#[cfg_attr(feature = "tracing", instrument(level = "debug", skip(self)))]
140	fn try_wait(&mut self) -> Result<Option<ExitStatus>> {
141		wait_on_job(self.job_port.completion_port, Some(Duration::ZERO))?;
142		self.inner.try_wait()
143	}
144}
process_wrap/std/job_object.rs

process_wrap/std/
job_object.rs
