docs: Add supported versions and fix-backport policy

[lttng-tools.git] / src / bin / lttng-sessiond / health.cpp

/*
 * Copyright (C) 2012 David Goulet <dgoulet@efficios.com>
 * Copyright (C) 2018 Jérémie Galarneau <jeremie.galarneau@efficios.com>
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 */

#include "health-sessiond.hpp"
#include "lttng-sessiond.hpp"
#include "thread.hpp"
#include "utils.hpp"

#include <common/error.hpp>
#include <common/macros.hpp>
#include <common/pipe.hpp>
#include <common/utils.hpp>

#include <fcntl.h>
#include <inttypes.h>
#include <sys/stat.h>

namespace {
struct thread_notifiers {
	struct lttng_pipe *quit_pipe;
	sem_t ready;
};
} /* namespace */

static void mark_thread_as_ready(struct thread_notifiers *notifiers)
{
	DBG("Marking health management thread as ready");
	sem_post(&notifiers->ready);
}

static void wait_until_thread_is_ready(struct thread_notifiers *notifiers)
{
	DBG("Waiting for health management thread to be ready");
	sem_wait(&notifiers->ready);
	DBG("Health management thread is ready");
}

static void cleanup_health_management_thread(void *data)
{
	struct thread_notifiers *notifiers = (thread_notifiers *) data;

	lttng_pipe_destroy(notifiers->quit_pipe);
	sem_destroy(&notifiers->ready);
	free(notifiers);
}

/*
 * Thread managing health check socket.
 */
static void *thread_manage_health(void *data)
{
	const bool is_root = (getuid() == 0);
	int sock = -1, new_sock = -1, ret, i, err = -1;
	uint32_t nb_fd;
	struct lttng_poll_event events;
	struct health_comm_msg msg;
	struct health_comm_reply reply;
	/* Thread-specific quit pipe. */
	struct thread_notifiers *notifiers = (thread_notifiers *) data;
	const auto thread_quit_pipe_fd = lttng_pipe_get_readfd(notifiers->quit_pipe);

	DBG("[thread] Manage health check started");

	rcu_register_thread();

	/*
	 * Created with a size of two for:
	 *   - health client socket
	 *   - thread quit pipe
	 */
	ret = lttng_poll_create(&events, 2, LTTNG_CLOEXEC);
	if (ret < 0) {
		goto error;
	}

	/* Create unix socket */
	sock = lttcomm_create_unix_sock(the_config.health_unix_sock_path.value);
	if (sock < 0) {
		ERR("Unable to create health check Unix socket");
		goto error;
	}

	if (is_root) {
		/* lttng health client socket path permissions */
		gid_t gid;

		ret = utils_get_group_id(the_config.tracing_group_name.value, true, &gid);
		if (ret) {
			/* Default to root group. */
			gid = 0;
		}

		ret = chown(the_config.health_unix_sock_path.value, 0, gid);
		if (ret < 0) {
			ERR("Unable to set group on %s", the_config.health_unix_sock_path.value);
			PERROR("chown");
			goto error;
		}

		ret = chmod(the_config.health_unix_sock_path.value,
			    S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
		if (ret < 0) {
			ERR("Unable to set permissions on %s",
			    the_config.health_unix_sock_path.value);
			PERROR("chmod");
			goto error;
		}
	}

	/*
	 * Set the CLOEXEC flag. Return code is useless because either way, the
	 * show must go on.
	 */
	(void) utils_set_fd_cloexec(sock);

	ret = lttcomm_listen_unix_sock(sock);
	if (ret < 0) {
		goto error;
	}

	ret = lttng_poll_add(&events, thread_quit_pipe_fd, LPOLLIN);
	if (ret < 0) {
		goto error;
	}

	/* Add the health client socket. */
	ret = lttng_poll_add(&events, sock, LPOLLIN | LPOLLPRI);
	if (ret < 0) {
		goto error;
	}

	mark_thread_as_ready(notifiers);
	while (true) {
		DBG("Health check ready");

		/* Infinite blocking call, waiting for transmission */
	restart:
		ret = lttng_poll_wait(&events, -1);
		if (ret < 0) {
			/*
			 * Restart interrupted system call.
			 */
			if (errno == EINTR) {
				goto restart;
			}
			goto error;
		}

		nb_fd = ret;

		for (i = 0; i < nb_fd; i++) {
			/* Fetch once the poll data */
			const auto revents = LTTNG_POLL_GETEV(&events, i);
			const auto pollfd = LTTNG_POLL_GETFD(&events, i);

			/* Activity on thread quit pipe, exiting. */
			if (pollfd == thread_quit_pipe_fd) {
				DBG("Activity on thread quit pipe");
				err = 0;
				goto exit;
			}

			/* Event on the health client socket. */
			if (revents & LPOLLIN) {
				continue;
			} else if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
				ERR("Health socket poll error");
				goto error;
			} else {
				ERR("Unexpected poll events %u for sock %d", revents, pollfd);
				goto error;
			}
		}

		new_sock = lttcomm_accept_unix_sock(sock);
		if (new_sock < 0) {
			goto error;
		}

		/*
		 * Set the CLOEXEC flag. Return code is useless because either way, the
		 * show must go on.
		 */
		(void) utils_set_fd_cloexec(new_sock);

		DBG("Receiving data from client for health...");
		ret = lttcomm_recv_unix_sock(new_sock, (void *) &msg, sizeof(msg));
		if (ret <= 0) {
			DBG("Nothing recv() from client... continuing");
			ret = close(new_sock);
			if (ret) {
				PERROR("close");
			}
			continue;
		}

		rcu_thread_online();

		memset(&reply, 0, sizeof(reply));
		for (i = 0; i < NR_HEALTH_SESSIOND_TYPES; i++) {
			/*
			 * health_check_state returns 0 if health is
			 * bad.
			 */
			if (!health_check_state(the_health_sessiond, i)) {
				reply.ret_code |= 1ULL << i;
			}
		}

		DBG2("Health check return value %" PRIx64, reply.ret_code);

		ret = lttcomm_send_unix_sock(new_sock, (void *) &reply, sizeof(reply));
		if (ret < 0) {
			ERR("Failed to send health data back to client");
		}

		/* End of transmission */
		ret = close(new_sock);
		if (ret) {
			PERROR("close");
		}
	}

exit:
error:
	if (err) {
		ERR("Health error occurred in %s", __func__);
	}
	DBG("Health check thread dying");
	unlink(the_config.health_unix_sock_path.value);
	if (sock >= 0) {
		ret = close(sock);
		if (ret) {
			PERROR("close");
		}
	}

	lttng_poll_clean(&events);
	rcu_unregister_thread();
	return nullptr;
}

static bool shutdown_health_management_thread(void *data)
{
	struct thread_notifiers *notifiers = (thread_notifiers *) data;
	const int write_fd = lttng_pipe_get_writefd(notifiers->quit_pipe);

	return notify_thread_pipe(write_fd) == 1;
}

bool launch_health_management_thread()
{
	struct thread_notifiers *notifiers;
	struct lttng_thread *thread;

	notifiers = zmalloc<thread_notifiers>();
	if (!notifiers) {
		goto error_alloc;
	}

	sem_init(&notifiers->ready, 0, 0);
	notifiers->quit_pipe = lttng_pipe_open(FD_CLOEXEC);
	if (!notifiers->quit_pipe) {
		goto error;
	}
	thread = lttng_thread_create("Health management",
				     thread_manage_health,
				     shutdown_health_management_thread,
				     cleanup_health_management_thread,
				     notifiers);
	if (!thread) {
		goto error;
	}

	wait_until_thread_is_ready(notifiers);
	lttng_thread_put(thread);
	return true;
error:
	cleanup_health_management_thread(notifiers);
error_alloc:
	return false;
}