Process Manager

Process Manager (procman) helps to create daemons and applications that is sensible to process properties. When the application starts in UNIX environment, it inherits a lot of process properties that are inappropriate for daemons and may be undesirable for some utilities.

Below are problems, that procman helps to solve:

• set_no_std_fd() redirects stdin, stdout and stderr to /dev/null. It is mandatory for security reasons. Suppose you forked daemon from your terminal and switched off the session. Now if the other user will login on the same terminal device, she will receive all daemon's output.
• set_work_dir(std::string) changes current working directory to given, or to "/" by default. Helps avoid hanging when some daemon blocks unmount the filesystem because it's working directory is on it.
• set_umask(int) sets file mode creation mask to a known value. Daemon shouldn't rely on the parent's one - it could be rwxrwxrwx.
• set_close_all_fd() closes all file descriptors to prevent unneded holdings.
• set_pid_file(std::string) cause the application to create PID file and lock it. It helps to run only one copy of the application.
• set_signals() call on_stop callback on SIGTERM, SIGQUIT SIGINT receiving instead of unexpected process termination.
• set_no_control_tty() disassociate the process from the calling terminal, make it leader of the new session and process group.
• You can initiate normal stop process from any thread of the program with help of process singleton.
• You can easy register some useful operations on receiving SIGHUP, SIGUSR1 or SIGUSR2.
• and others ...

You don't have to do all the listed above. You can configure exactly what you need for your particular case - see "Example: fine tuning".

Building

The library is very small - just one cpp file. You can build it as usual library with help of cmake:

cd ~
git clone https://github.com/hoxnox/procman
cd ~/procman
mkdir build
cd build
cmake -DCMAKE_INSTALL_PREFIX=/path/to/procman ..
make install 
g++ -std=c++11 -I /path/to/procman/include -L /path/to/procman/lib test.cpp -l procman

or by hand:

cd ~
git clone https://github.com/hoxnox/procman
g++ -std=c++11 -I ~/procman/include -c -o procman.o ~/procman/src/procman.cpp
g++ -std=c++11 -I ~/procman/include test.cpp ptocman.o

Examples

Watch your messages:

sudo tail -f /var/log/messages

Launch the example and play with it - try to launch several copies, send signals with help of kill:

kill -s SIGHUP <PID>

daemonize

The code below is fully functional daemon with PID at /tmp/my_daemon.pid.

Default daemonize set PID at /var/run/<name>.pid. But I decided to change this location to /tmp/my_daemon.pid - in that case you don't need root privileges to start the daemon.

#include <syslog.h>
#include <unistd.h>

#include <procman.hpp>

using namespace procman;

int
main(int argc, char* argv[])
{
	bool stop = false;
	openlog("my_daemon", 0, LOG_USER);
	auto pm = proc_builder("my_daemon").daemonize()
		.set_pid_file("/tmp/my_daemon.pid")
		.on_stop([&stop](){ syslog(LOG_INFO, "stopped"); stop = true; })
		.on_hup([](){ syslog(LOG_INFO, "config update"); })
		.on_start([&stop]()
			{
				syslog(LOG_INFO, "started");
				while (!stop)
					usleep(100);
			});
	if (!pm.start())
		syslog(LOG_ERR, "Process error: %s", pm.strerror().c_str());
	return 0;
}

fine tuning

Try to start several instances and send them SIGHUP and SIGTERM.

#include <syslog.h>
#include <unistd.h>
#include <iostream>

#include <procman.hpp>

using namespace procman;

int
main(int argc, char* argv[])
{
	bool stop = false;
	openlog("my_daemon", 0, LOG_USER);
	auto pm = proc_builder("my_daemon")
		.set_work_dir("/tmp")
		.set_no_control_tty()
		.on_stop([&stop](process::stop_reason_t reason)
			{
				if (reason == process::STOP_SIGNAL)
					syslog(LOG_INFO, "stopped signal");
				syslog(LOG_INFO, "stopped normal");
				stop = true;
			})
		.on_hup([](std::shared_ptr<process> p) // set_signals() automatically
			{
				syslog(LOG_ERR, "imagine error, normal stop");
				p->stop();
			})
		.on_start([&stop]()
			{
				syslog(LOG_INFO, "started");
				std::cout << getpid() << std::endl;
				while (!stop)
					usleep(100);
			});
	if (!pm.start())
		syslog(LOG_ERR, "Process error: %s", pm.strerror().c_str());
	return 0;
}