mm::auto_tuning::detail Namespace Reference

Classes
struct	Child
	A started child, as the platform identifies it. More...

Functions
std::expected< Child, std::string >	spawnChild (const std::filesystem::path &binary, const std::vector< std::string > &args, const std::filesystem::path &logFile)
	Runs binary with args, with its output appended to logFile.
bool	childAlive (const Child &child)
	Whether child is still running.
bool	terminateChild (const Child &child, std::chrono::milliseconds grace)
	Asks child to exit, waits up to grace, then kills it and everything it started.

Function Documentation

childAlive()

bool mm::auto_tuning::detail::childAlive

(

const Child &

child

)

Whether child is still running.

This reaps a child that exited, which is how the exit is detected at all, and it is why only Process::start calls it: a reaped process id may be reissued to an unrelated process, so the caller must forget the child as soon as this returns false.

spawnChild()

std::expected< Child, std::string > mm::auto_tuning::detail::spawnChild	(	const std::filesystem::path &	binary,
		const std::vector< std::string > &	args,
		const std::filesystem::path &	logFile
	)

Runs binary with args, with its output appended to logFile.

The child inherits this process's stdout and stderr when logFile is empty. It never inherits stdin: the auto-tuning program reads none, and a child sharing a terminal's stdin can stop the whole process group.

Returns

The started child, or an error string. A missing or non-executable binary is reported here, by the platform, rather than pre-checked — a check followed by a spawn would still have to handle the spawn failing.

terminateChild()

bool mm::auto_tuning::detail::terminateChild	(	const Child &	child,
		std::chrono::milliseconds	grace
	)

Asks child to exit, waits up to grace, then kills it and everything it started.

Returns once the child is gone. The auto-tuning program handles a termination signal and shuts its server down; the kill is for a child wedged inside a numerical routine, and it takes the whole group so that nothing is left holding the port.

Returns

false when the signal was enough, true when the kill was needed. The caller logs the difference: a child that ignores a termination signal is worth knowing about, and it is the case where a leftover process could hold the port against the next start.