isc::asiolink::ProcessSpawn Class Reference

Utility class for spawning new processes. More...

#include <process_spawn.h>

Inheritance diagram for isc::asiolink::ProcessSpawn:

Public Types
enum	SpawnMode { ASYNC , SYNC }
	The spawn type. More...

Public Member Functions
	ProcessSpawn (const SpawnMode mode, const std::string &executable, const ProcessArgs &args=ProcessArgs(), const ProcessEnvVars &vars=ProcessEnvVars(), const bool inherit_env=false)
	Constructor.
	~ProcessSpawn ()=default
	Destructor.
void	clearState (const pid_t pid)
	Removes the status of the process with a specified PID.
std::string	getCommandLine () const
	Returns full command line, including arguments, for the process.
int	getExitStatus (const pid_t pid) const
	Returns exit status of the process.
bool	isAnyRunning () const
	Checks if any of the spawned processes is still running.
bool	isRunning (const pid_t pid) const
	Checks if the process is still running.
pid_t	spawn (bool dismiss=false)
	Spawn the new process.

Static Public Member Functions
static isc::asiolink::IOServicePtr	getIOService ()
	Get the I/O service.
static void	setIOService (isc::asiolink::IOServicePtr io_service)
	Set the I/O service.

Detailed Description

Utility class for spawning new processes.

This class is used to spawn new process by Kea. It forks the current process and then uses the execve function to execute the specified binary with parameters. The ProcessSpawn installs the handler for the SIGCHLD signal, which is executed when the child process ends. The handler checks the exit code returned by the process and records it. The exit code can be retrieved by the caller using the ProcessSpawn::getExitStatus method.

This class is made noncopyable so that we don't have attempts to make multiple copies of an object. This avoid problems with multiple copies of objects for a single global resource such as the SIGCHLD signal handler. In addition making it noncopyable keeps the static check code from flagging the lack of a copy constructor as an issue.

Note

The ProcessSpawn uses full path for the program to execute.

Definition at line 61 of file process_spawn.h.

Member Enumeration Documentation

SpawnMode

enum isc::asiolink::ProcessSpawn::SpawnMode

The spawn type.

Enumerator
ASYNC
SYNC

Definition at line 65 of file process_spawn.h.

Constructor & Destructor Documentation

ProcessSpawn()

isc::asiolink::ProcessSpawn::ProcessSpawn	(	const SpawnMode	mode,
		const std::string &	executable,
		const ProcessArgs &	args = ProcessArgs(),
		const ProcessEnvVars &	vars = ProcessEnvVars(),
		const bool	inherit_env = false )

Constructor.

Parameters

mode	specifies synchronous or asynchronous mode.
executable	A full path to the program to be executed.
args	Arguments for the program to be executed.
vars	Environment variables for the program to be executed.
inherit_env	whether the spawned process will inherit the environment before adding 'vars' on top.

Definition at line 483 of file process_spawn.cc.

~ProcessSpawn()

isc::asiolink::ProcessSpawn::~ProcessSpawn ( )

default

Destructor.

Member Function Documentation

clearState()

void isc::asiolink::ProcessSpawn::clearState

(

const pid_t

pid

)

Removes the status of the process with a specified PID.

This method removes the status of the process with a specified PID. If the process is still running, the status is not removed and the exception is thrown.

Note ProcessSpawn::isRunning must be called and have returned false before using clearState(). And of course ProcessSpawn::getExitStatus should be called first, if there is some interest in the status.

Parameters

pid	A process pid.

Definition at line 517 of file process_spawn.cc.

getCommandLine()

std::string isc::asiolink::ProcessSpawn::getCommandLine

(

)

const

Returns full command line, including arguments, for the process.

Definition at line 492 of file process_spawn.cc.

getExitStatus()

int isc::asiolink::ProcessSpawn::getExitStatus

(

const pid_t

pid

)

const

Returns exit status of the process.

If the process is still running, the previous status is returned or 0, if the process is being ran for the first time.

Note

ProcessSpawn::isRunning should be called and have returned false before using ProcessSpawn::getExitStatus.

Parameters

pid	ID of the child process for which exit status should be returned.

Returns

Exit code of the process.

Definition at line 512 of file process_spawn.cc.

getIOService()

static isc::asiolink::IOServicePtr isc::asiolink::ProcessSpawn::getIOService ( )

inlinestatic

Get the I/O service.

Returns

the I/O service.

Definition at line 152 of file process_spawn.h.

Referenced by isc::asiolink::ProcessSpawnImpl::spawn().

isAnyRunning()

bool isc::asiolink::ProcessSpawn::isAnyRunning

(

)

const

Checks if any of the spawned processes is still running.

Returns

true if at least one child process is still running.

Definition at line 507 of file process_spawn.cc.

isRunning()

bool isc::asiolink::ProcessSpawn::isRunning

(

const pid_t

pid

)

const

Checks if the process is still running.

Note that only a negative (false) result is reliable as the child process can exit between the time its state is checked and this function returns.

Parameters

pid	ID of the child processes for which state should be checked.

Returns

true if the child process is running, false otherwise.

Definition at line 502 of file process_spawn.cc.

setIOService()

static void isc::asiolink::ProcessSpawn::setIOService ( isc::asiolink::IOServicePtr io_service )

inlinestatic

Set the I/O service.

Parameters

io_service

the I/O service.

Definition at line 159 of file process_spawn.h.

Referenced by isc::dhcp::ControlledDhcpv4Srv::ControlledDhcpv4Srv(), and isc::dhcp::ControlledDhcpv6Srv::ControlledDhcpv6Srv().

spawn()

pid_t isc::asiolink::ProcessSpawn::spawn

(

bool

dismiss = false

)

Spawn the new process.

This method forks the current process and executes the specified binary with arguments within the child process.

The child process will return EXIT_FAILURE if the method was unable to start the executable, e.g. as a result of insufficient permissions or when the executable does not exist. If the process ends successfully the EXIT_SUCCESS is returned.

Parameters

dismiss

The flag which indicated if the process status can be disregarded.

Exceptions

ProcessSpawnError

if forking a current process failed.

Definition at line 497 of file process_spawn.cc.

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The documentation for this class was generated from the following files:

• process_spawn.h
• process_spawn.cc