src/spawn/spawn_server.c
// SPDX-License-Identifier: GPL-3.0-or-later
#include "spawn.h"
static uv_loop_t *loop;
static uv_pipe_t server_pipe;
static int server_shutdown = 0;
static uv_thread_t thread;
/* spawn outstanding execution structure */
static avl_tree_lock spawn_outstanding_exec_tree;
static char prot_buffer[MAX_COMMAND_LENGTH];
static unsigned prot_buffer_len = 0;
struct spawn_execution_info {
avl_t avl;
void *handle;
int exit_status;
pid_t pid;
struct spawn_execution_info *next;
};
int spawn_exec_compare(void *a, void *b)
{
struct spawn_execution_info *spwna = a, *spwnb = b;
if (spwna->pid < spwnb->pid) return -1;
if (spwna->pid > spwnb->pid) return 1;
return 0;
}
/* wake up waiter thread to reap the spawned processes */
static uv_mutex_t wait_children_mutex;
static uv_cond_t wait_children_cond;
static uint8_t spawned_processes;
static struct spawn_execution_info *child_waited_list;
static uv_async_t child_waited_async;
static inline struct spawn_execution_info *dequeue_child_waited_list(void)
{
struct spawn_execution_info *exec_info;
uv_mutex_lock(&wait_children_mutex);
if (NULL == child_waited_list) {
exec_info = NULL;
} else {
exec_info = child_waited_list;
child_waited_list = exec_info->next;
}
uv_mutex_unlock(&wait_children_mutex);
return exec_info;
}
static inline void enqueue_child_waited_list(struct spawn_execution_info *exec_info)
{
uv_mutex_lock(&wait_children_mutex);
exec_info->next = child_waited_list;
child_waited_list = exec_info;
uv_mutex_unlock(&wait_children_mutex);
}
static void after_pipe_write(uv_write_t *req, int status)
{
(void)status;
#ifdef SPAWN_DEBUG
fprintf(stderr, "SERVER %s called status=%d\n", __func__, status);
#endif
void **data = req->data;
freez(data[0]);
freez(data[1]);
freez(data);
}
static void child_waited_async_cb(uv_async_t *async_handle)
{
uv_buf_t *writebuf;
int ret;
struct spawn_execution_info *exec_info;
struct write_context *write_ctx;
(void)async_handle;
while (NULL != (exec_info = dequeue_child_waited_list())) {
write_ctx = mallocz(sizeof(*write_ctx));
void **data = callocz(2, sizeof(void *));
writebuf = callocz(2, sizeof(uv_buf_t));
data[0] = write_ctx;
data[1] = writebuf;
write_ctx->write_req.data = data;
write_ctx->header.opcode = SPAWN_PROT_CMD_EXIT_STATUS;
write_ctx->header.handle = exec_info->handle;
write_ctx->exit_status.exec_exit_status = exec_info->exit_status;
writebuf[0] = uv_buf_init((char *) &write_ctx->header, sizeof(write_ctx->header));
writebuf[1] = uv_buf_init((char *) &write_ctx->exit_status, sizeof(write_ctx->exit_status));
#ifdef SPAWN_DEBUG
fprintf(stderr, "SERVER %s SPAWN_PROT_CMD_EXIT_STATUS\n", __func__);
#endif
ret = uv_write(&write_ctx->write_req, (uv_stream_t *) &server_pipe, writebuf, 2, after_pipe_write);
fatal_assert(ret == 0);
freez(exec_info);
}
}
static void wait_children(void *arg)
{
siginfo_t i;
struct spawn_execution_info tmp, *exec_info;
avl_t *ret_avl;
(void)arg;
while (!server_shutdown) {
uv_mutex_lock(&wait_children_mutex);
while (!spawned_processes) {
uv_cond_wait(&wait_children_cond, &wait_children_mutex);
}
spawned_processes = 0;
uv_mutex_unlock(&wait_children_mutex);
while (!server_shutdown) {
i.si_pid = 0;
if (os_waitid(P_ALL, (id_t) 0, &i, WEXITED) == -1) {
if (errno != ECHILD)
fprintf(stderr, "SPAWN: Failed to wait: %s\n", strerror(errno));
break;
}
if (i.si_pid == 0) {
fprintf(stderr, "SPAWN: No child exited.\n");
break;
}
#ifdef SPAWN_DEBUG
fprintf(stderr, "SPAWN: Successfully waited for pid:%d.\n", (int) i.si_pid);
#endif
fatal_assert(CLD_EXITED == i.si_code);
tmp.pid = (pid_t)i.si_pid;
while (NULL == (ret_avl = avl_remove_lock(&spawn_outstanding_exec_tree, (avl_t *)&tmp))) {
fprintf(stderr,
"SPAWN: race condition detected, waiting for child process %d to be indexed.\n",
(int)tmp.pid);
(void)sleep_usec(10000); /* 10 msec */
}
exec_info = (struct spawn_execution_info *)ret_avl;
exec_info->exit_status = i.si_status;
enqueue_child_waited_list(exec_info);
/* wake up event loop */
fatal_assert(0 == uv_async_send(&child_waited_async));
}
}
}
void spawn_protocol_execute_command(void *handle, char *command_to_run, uint16_t command_length)
{
uv_buf_t *writebuf;
int ret;
avl_t *avl_ret;
struct spawn_execution_info *exec_info;
struct write_context *write_ctx;
write_ctx = mallocz(sizeof(*write_ctx));
void **data = callocz(2, sizeof(void *));
writebuf = callocz(2, sizeof(uv_buf_t));
data[0] = write_ctx;
data[1] = writebuf;
write_ctx->write_req.data = data;
command_to_run[command_length] = '\0';
#ifdef SPAWN_DEBUG
fprintf(stderr, "SPAWN: executing command '%s'\n", command_to_run);
#endif
if (netdata_spawn(command_to_run, &write_ctx->spawn_result.exec_pid)) {
fprintf(stderr, "SPAWN: Cannot spawn(\"%s\", \"r\").\n", command_to_run);
write_ctx->spawn_result.exec_pid = 0;
} else { /* successfully spawned command */
write_ctx->spawn_result.exec_run_timestamp = now_realtime_sec();
/* record it for when the process finishes execution */
exec_info = mallocz(sizeof(*exec_info));
exec_info->handle = handle;
exec_info->pid = write_ctx->spawn_result.exec_pid;
avl_ret = avl_insert_lock(&spawn_outstanding_exec_tree, (avl_t *)exec_info);
fatal_assert(avl_ret == (avl_t *)exec_info);
/* wake up the thread that blocks waiting for processes to exit */
uv_mutex_lock(&wait_children_mutex);
spawned_processes = 1;
uv_cond_signal(&wait_children_cond);
uv_mutex_unlock(&wait_children_mutex);
}
write_ctx->header.opcode = SPAWN_PROT_SPAWN_RESULT;
write_ctx->header.handle = handle;
writebuf[0] = uv_buf_init((char *)&write_ctx->header, sizeof(write_ctx->header));
writebuf[1] = uv_buf_init((char *)&write_ctx->spawn_result, sizeof(write_ctx->spawn_result));
#ifdef SPAWN_DEBUG
fprintf(stderr, "SERVER %s SPAWN_PROT_SPAWN_RESULT\n", __func__);
#endif
ret = uv_write(&write_ctx->write_req, (uv_stream_t *)&server_pipe, writebuf, 2, after_pipe_write);
fatal_assert(ret == 0);
}
static void server_parse_spawn_protocol(unsigned source_len, char *source)
{
unsigned required_len;
struct spawn_prot_header *header;
struct spawn_prot_exec_cmd *payload;
uint16_t command_length;
while (source_len) {
required_len = sizeof(*header);
if (prot_buffer_len < required_len)
copy_to_prot_buffer(prot_buffer, &prot_buffer_len, required_len - prot_buffer_len, &source, &source_len);
if (prot_buffer_len < required_len)
return; /* Source buffer ran out */
header = (struct spawn_prot_header *)prot_buffer;
fatal_assert(SPAWN_PROT_EXEC_CMD == header->opcode);
fatal_assert(NULL != header->handle);
required_len += sizeof(*payload);
if (prot_buffer_len < required_len)
copy_to_prot_buffer(prot_buffer, &prot_buffer_len, required_len - prot_buffer_len, &source, &source_len);
if (prot_buffer_len < required_len)
return; /* Source buffer ran out */
payload = (struct spawn_prot_exec_cmd *)(header + 1);
command_length = payload->command_length;
required_len += command_length;
if (unlikely(required_len > MAX_COMMAND_LENGTH - 1)) {
fprintf(stderr, "SPAWN: Ran out of protocol buffer space.\n");
command_length = (MAX_COMMAND_LENGTH - 1) - (sizeof(*header) + sizeof(*payload));
required_len = MAX_COMMAND_LENGTH - 1;
}
if (prot_buffer_len < required_len)
copy_to_prot_buffer(prot_buffer, &prot_buffer_len, required_len - prot_buffer_len, &source, &source_len);
if (prot_buffer_len < required_len)
return; /* Source buffer ran out */
spawn_protocol_execute_command(header->handle, payload->command_to_run, command_length);
prot_buffer_len = 0;
}
}
static void on_pipe_read(uv_stream_t *pipe, ssize_t nread, const uv_buf_t *buf)
{
if (0 == nread) {
fprintf(stderr, "SERVER %s: Zero bytes read from spawn pipe.\n", __func__);
} else if (UV_EOF == nread) {
fprintf(stderr, "EOF found in spawn pipe.\n");
} else if (nread < 0) {
fprintf(stderr, "%s: %s\n", __func__, uv_strerror(nread));
}
if (nread < 0) { /* stop spawn server due to EOF or error */
int error;
uv_mutex_lock(&wait_children_mutex);
server_shutdown = 1;
spawned_processes = 1;
uv_cond_signal(&wait_children_cond);
uv_mutex_unlock(&wait_children_mutex);
fprintf(stderr, "Shutting down spawn server event loop.\n");
/* cleanup operations of the event loop */
(void)uv_read_stop((uv_stream_t *) pipe);
uv_close((uv_handle_t *)&server_pipe, NULL);
error = uv_thread_join(&thread);
if (error) {
fprintf(stderr, "uv_thread_create(): %s", uv_strerror(error));
}
/* After joining it is safe to destroy child_waited_async */
uv_close((uv_handle_t *)&child_waited_async, NULL);
} else if (nread) {
#ifdef SPAWN_DEBUG
fprintf(stderr, "SERVER %s nread %u\n", __func__, (unsigned)nread);
#endif
server_parse_spawn_protocol(nread, buf->base);
}
if (buf && buf->len) {
freez(buf->base);
}
}
static void on_read_alloc(uv_handle_t *handle,
size_t suggested_size,
uv_buf_t* buf)
{
(void)handle;
buf->base = mallocz(suggested_size);
buf->len = suggested_size;
}
static void ignore_signal_handler(int signo) {
/*
* By having a signal handler we allow spawned processes to reset default signal dispositions. Setting SIG_IGN
* would be inherited by the spawned children which is not desirable.
*/
(void)signo;
}
void spawn_server(void)
{
int error;
// initialize the system clocks
clocks_init();
// close all open file descriptors, except the standard ones
// the caller may have left open files (lxc-attach has this issue)
for_each_open_fd(OPEN_FD_ACTION_CLOSE, OPEN_FD_EXCLUDE_STDIN | OPEN_FD_EXCLUDE_STDOUT | OPEN_FD_EXCLUDE_STDERR);
// Have the libuv IPC pipe be closed when forking child processes
(void) fcntl(0, F_SETFD, FD_CLOEXEC);
fprintf(stderr, "Spawn server is up.\n");
// Define signals we want to ignore
struct sigaction sa;
int signals_to_ignore[] = {SIGPIPE, SIGINT, SIGQUIT, SIGTERM, SIGHUP, SIGUSR1, SIGUSR2, SIGBUS, SIGCHLD};
unsigned ignore_length = sizeof(signals_to_ignore) / sizeof(signals_to_ignore[0]);
unsigned i;
for (i = 0; i < ignore_length ; ++i) {
sa.sa_flags = 0;
sigemptyset(&sa.sa_mask);
sa.sa_handler = ignore_signal_handler;
if(sigaction(signals_to_ignore[i], &sa, NULL) == -1)
fprintf(stderr, "SPAWN: Failed to change signal handler for signal: %d.\n", signals_to_ignore[i]);
}
signals_unblock();
loop = uv_default_loop();
loop->data = NULL;
error = uv_pipe_init(loop, &server_pipe, 1);
if (error) {
fprintf(stderr, "uv_pipe_init(): %s\n", uv_strerror(error));
exit(error);
}
fatal_assert(server_pipe.ipc);
error = uv_pipe_open(&server_pipe, 0 /* UV_STDIN_FD */);
if (error) {
fprintf(stderr, "uv_pipe_open(): %s\n", uv_strerror(error));
exit(error);
}
avl_init_lock(&spawn_outstanding_exec_tree, spawn_exec_compare);
spawned_processes = 0;
fatal_assert(0 == uv_cond_init(&wait_children_cond));
fatal_assert(0 == uv_mutex_init(&wait_children_mutex));
child_waited_list = NULL;
error = uv_async_init(loop, &child_waited_async, child_waited_async_cb);
if (error) {
fprintf(stderr, "uv_async_init(): %s\n", uv_strerror(error));
exit(error);
}
error = uv_thread_create(&thread, wait_children, NULL);
if (error) {
fprintf(stderr, "uv_thread_create(): %s\n", uv_strerror(error));
exit(error);
}
prot_buffer_len = 0;
error = uv_read_start((uv_stream_t *)&server_pipe, on_read_alloc, on_pipe_read);
fatal_assert(error == 0);
while (!server_shutdown) {
uv_run(loop, UV_RUN_DEFAULT);
}
fprintf(stderr, "Shutting down spawn server loop complete.\n");
fatal_assert(0 == uv_loop_close(loop));
exit(0);
}