1 files changed, 288 insertions, 0 deletions
diff --git a/src/spawn/spawn.c b/src/spawn/spawn.c
new file mode 100644
index 000000000..a6e53718a
--- /dev/null
+++ b/src/spawn/spawn.c
@@ -0,0 +1,288 @@
+// 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.");
+}