src/spawn/spawn.c
// SPDX-License-Identifier: GPL-3.0-or-later
#include "spawn.h"
static uv_thread_t thread;
int spawn_thread_error;
int spawn_thread_shutdown;
struct spawn_queue spawn_cmd_queue;
static struct spawn_cmd_info *create_spawn_cmd(const char *command_to_run)
{
struct spawn_cmd_info *cmdinfo;
cmdinfo = mallocz(sizeof(*cmdinfo));
fatal_assert(0 == uv_cond_init(&cmdinfo->cond));
fatal_assert(0 == uv_mutex_init(&cmdinfo->mutex));
cmdinfo->serial = 0; /* invalid */
cmdinfo->command_to_run = strdupz(command_to_run);
cmdinfo->exit_status = -1; /* invalid */
cmdinfo->pid = -1; /* invalid */
cmdinfo->flags = 0;
return cmdinfo;
}
void destroy_spawn_cmd(struct spawn_cmd_info *cmdinfo)
{
uv_cond_destroy(&cmdinfo->cond);
uv_mutex_destroy(&cmdinfo->mutex);
freez(cmdinfo->command_to_run);
freez(cmdinfo);
}
int spawn_cmd_compare(void *a, void *b)
{
struct spawn_cmd_info *cmda = a, *cmdb = b;
/* No need for mutex, serial will never change and the entries cannot be deallocated yet */
if (cmda->serial < cmdb->serial) return -1;
if (cmda->serial > cmdb->serial) return 1;
return 0;
}
static void init_spawn_cmd_queue(void)
{
spawn_cmd_queue.cmd_tree.root = NULL;
spawn_cmd_queue.cmd_tree.compar = spawn_cmd_compare;
spawn_cmd_queue.size = 0;
spawn_cmd_queue.latest_serial = 0;
fatal_assert(0 == uv_cond_init(&spawn_cmd_queue.cond));
fatal_assert(0 == uv_mutex_init(&spawn_cmd_queue.mutex));
}
/*
* Returns serial number of the enqueued command
*/
uint64_t spawn_enq_cmd(const char *command_to_run)
{
unsigned queue_size;
uint64_t serial;
avl_t *avl_ret;
struct spawn_cmd_info *cmdinfo;
cmdinfo = create_spawn_cmd(command_to_run);
/* wait for free space in queue */
uv_mutex_lock(&spawn_cmd_queue.mutex);
while ((queue_size = spawn_cmd_queue.size) == SPAWN_MAX_OUTSTANDING) {
uv_cond_wait(&spawn_cmd_queue.cond, &spawn_cmd_queue.mutex);
}
fatal_assert(queue_size < SPAWN_MAX_OUTSTANDING);
spawn_cmd_queue.size = queue_size + 1;
serial = ++spawn_cmd_queue.latest_serial; /* 0 is invalid */
cmdinfo->serial = serial; /* No need to take the cmd mutex since it is unreachable at the moment */
/* enqueue command */
avl_ret = avl_insert(&spawn_cmd_queue.cmd_tree, (avl_t *)cmdinfo);
fatal_assert(avl_ret == (avl_t *)cmdinfo);
uv_mutex_unlock(&spawn_cmd_queue.mutex);
/* wake up event loop */
fatal_assert(0 == uv_async_send(&spawn_async));
return serial;
}
/*
* Blocks until command with serial finishes running. Only one thread is allowed to wait per command.
*/
void spawn_wait_cmd(uint64_t serial, int *exit_status, time_t *exec_run_timestamp)
{
avl_t *avl_ret;
struct spawn_cmd_info tmp, *cmdinfo;
tmp.serial = serial;
uv_mutex_lock(&spawn_cmd_queue.mutex);
avl_ret = avl_search(&spawn_cmd_queue.cmd_tree, (avl_t *)&tmp);
uv_mutex_unlock(&spawn_cmd_queue.mutex);
fatal_assert(avl_ret); /* Could be NULL if more than 1 threads wait for the command */
cmdinfo = (struct spawn_cmd_info *)avl_ret;
uv_mutex_lock(&cmdinfo->mutex);
while (!(cmdinfo->flags & SPAWN_CMD_DONE)) {
/* Only 1 thread is allowed to wait for this command to finish */
uv_cond_wait(&cmdinfo->cond, &cmdinfo->mutex);
}
uv_mutex_unlock(&cmdinfo->mutex);
spawn_deq_cmd(cmdinfo);
*exit_status = cmdinfo->exit_status;
*exec_run_timestamp = cmdinfo->exec_run_timestamp;
destroy_spawn_cmd(cmdinfo);
}
void spawn_deq_cmd(struct spawn_cmd_info *cmdinfo)
{
unsigned queue_size;
avl_t *avl_ret;
uv_mutex_lock(&spawn_cmd_queue.mutex);
queue_size = spawn_cmd_queue.size;
fatal_assert(queue_size);
/* dequeue command */
avl_ret = avl_remove(&spawn_cmd_queue.cmd_tree, (avl_t *)cmdinfo);
fatal_assert(avl_ret);
spawn_cmd_queue.size = queue_size - 1;
/* wake up callers */
uv_cond_signal(&spawn_cmd_queue.cond);
uv_mutex_unlock(&spawn_cmd_queue.mutex);
}
/*
* Must be called from the spawn client event loop context. This way no mutex is needed because the event loop is the
* only writer as far as struct spawn_cmd_info entries are concerned.
*/
static int find_unprocessed_spawn_cmd_cb(void *entry, void *data)
{
struct spawn_cmd_info **cmdinfop = data, *cmdinfo = entry;
if (!(cmdinfo->flags & SPAWN_CMD_PROCESSED)) {
*cmdinfop = cmdinfo;
return -1; /* break tree traversal */
}
return 0; /* continue traversing */
}
struct spawn_cmd_info *spawn_get_unprocessed_cmd(void)
{
struct spawn_cmd_info *cmdinfo;
unsigned queue_size;
int ret;
uv_mutex_lock(&spawn_cmd_queue.mutex);
queue_size = spawn_cmd_queue.size;
if (queue_size == 0) {
uv_mutex_unlock(&spawn_cmd_queue.mutex);
return NULL;
}
/* find command */
cmdinfo = NULL;
ret = avl_traverse(&spawn_cmd_queue.cmd_tree, find_unprocessed_spawn_cmd_cb, (void *)&cmdinfo);
if (-1 != ret) { /* no commands available for processing */
uv_mutex_unlock(&spawn_cmd_queue.mutex);
return NULL;
}
uv_mutex_unlock(&spawn_cmd_queue.mutex);
return cmdinfo;
}
/**
* This function spawns a process that shares a libuv IPC pipe with the caller and performs spawn server duties.
* The spawn server process will close all open file descriptors except for the pipe, UV_STDOUT_FD, and UV_STDERR_FD.
* The caller has to be the netdata user as configured.
*
* @param loop the libuv loop of the caller context
* @param spawn_channel the bidirectional libuv IPC pipe that the server and the caller will share
* @param process the spawn server libuv process context
* @return 0 on success or the libuv error code
*/
int create_spawn_server(uv_loop_t *loop, uv_pipe_t *spawn_channel, uv_process_t *process)
{
uv_process_options_t options = {0};
char *args[3];
int ret;
#define SPAWN_SERVER_DESCRIPTORS (3)
uv_stdio_container_t stdio[SPAWN_SERVER_DESCRIPTORS];
struct passwd *passwd = NULL;
char *user = NULL;
passwd = getpwuid(getuid());
user = (passwd && passwd->pw_name) ? passwd->pw_name : "";
args[0] = netdata_exe_file;
args[1] = SPAWN_SERVER_COMMAND_LINE_ARGUMENT;
args[2] = NULL;
memset(&options, 0, sizeof(options));
options.file = netdata_exe_file;
options.args = args;
options.exit_cb = NULL; //exit_cb;
options.stdio = stdio;
options.stdio_count = SPAWN_SERVER_DESCRIPTORS;
stdio[0].flags = UV_CREATE_PIPE | UV_READABLE_PIPE | UV_WRITABLE_PIPE;
stdio[0].data.stream = (uv_stream_t *)spawn_channel; /* bidirectional libuv pipe */
stdio[1].flags = UV_INHERIT_FD;
stdio[1].data.fd = 1 /* UV_STDOUT_FD */;
stdio[2].flags = UV_INHERIT_FD;
stdio[2].data.fd = nd_log_health_fd() /* UV_STDERR_FD */;
ret = uv_spawn(loop, process, &options); /* execute the netdata binary again as the netdata user */
if (0 != ret) {
netdata_log_error("uv_spawn (process: \"%s\") (user: %s) failed (%s).", netdata_exe_file, user, uv_strerror(ret));
fatal("Cannot start netdata without the spawn server.");
}
return ret;
}
#define CONCURRENT_SPAWNS 16
#define SPAWN_ITERATIONS 10000
#undef CONCURRENT_STRESS_TEST
void spawn_init(void)
{
struct completion completion;
int error;
netdata_log_info("Initializing spawn client.");
init_spawn_cmd_queue();
completion_init(&completion);
error = uv_thread_create(&thread, spawn_client, &completion);
if (error) {
netdata_log_error("uv_thread_create(): %s", uv_strerror(error));
goto after_error;
}
/* wait for spawn client thread to initialize */
completion_wait_for(&completion);
completion_destroy(&completion);
if (spawn_thread_error) {
error = uv_thread_join(&thread);
if (error) {
netdata_log_error("uv_thread_create(): %s", uv_strerror(error));
}
goto after_error;
}
#ifdef CONCURRENT_STRESS_TEST
signals_reset();
signals_unblock();
sleep(60);
uint64_t serial[CONCURRENT_SPAWNS];
for (int j = 0 ; j < SPAWN_ITERATIONS ; ++j) {
for (int i = 0; i < CONCURRENT_SPAWNS; ++i) {
char cmd[64];
sprintf(cmd, "echo CONCURRENT_STRESS_TEST %d 1>&2", j * CONCURRENT_SPAWNS + i + 1);
serial[i] = spawn_enq_cmd(cmd);
netdata_log_info("Queued command %s for spawning.", cmd);
}
int exit_status;
time_t exec_run_timestamp;
for (int i = 0; i < CONCURRENT_SPAWNS; ++i) {
netdata_log_info("Started waiting for serial %llu exit status %d run timestamp %llu.", serial[i], exit_status,
exec_run_timestamp);
spawn_wait_cmd(serial[i], &exit_status, &exec_run_timestamp);
netdata_log_info("Finished waiting for serial %llu exit status %d run timestamp %llu.", serial[i], exit_status,
exec_run_timestamp);
}
}
exit(0);
#endif
return;
after_error:
netdata_log_error("Failed to initialize spawn service. The alarms notifications will not be spawned.");
}