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confd: skip bootstrap on restart using a sentinel file

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After a successful bootstrap confd writes a sentinel to /run/confd.boot
If Finit restarts confd — whether after a crash or a clean exit — the
sentinel is found and the destructive bootstrap phases are skipped:

 - gen-config fork (factory/failure configs already exist)
 - wipe_sysrepo_shm() (other daemons, e.g. statd, are live)
 - sr_install_factory_config() (datastores are already initialised)
 - sr_replace_config(NULL, NULL) (running datastore is consistent)
 - bootstrap_config() / load startup-config (not needed; sysrepo has
   the right state; plugins resync via SR_EV_ENABLED on re-subscribe)

On restart confd reconnects to sysrepo, re-initialises plugins (which
re-subscribe and receive SR_EV_ENABLED to resync with the live running
datastore), then enters the steady-state event loop.

The sentinel lives on tmpfs so a real reboot always produces a clean
slate.  Crash-loop protection is delegated to Finit's max-restarts (10).

As a side-effect this also enables a future "run-once" mode for resource
constrained systems: confd can exit after bootstrap and the sentinel
ensures any later restart just re-attaches without re-bootstrapping.

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>
This commit is contained in:
Joachim Wiberg
2026-03-20 16:18:15 +01:00
parent ed1d6b7d5c
commit 7b4e9b3366
1 changed files with 111 additions and 65 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/confd/src/main.c
+111 -65
View File
@@ -39,6 +39,16 @@
/* Maximum number of sysrepo event pipe file descriptors across all plugins */
#define MAX_EVENT_FDS 64
/*
* Restart sentinel: written to tmpfs after a successful bootstrap.
* Survives crash and clean exit within the same boot session (cleared by
* reboot since /run is tmpfs). On restart confd detects it and skips the
* destructive bootstrap phases (gen-config, SHM wipe, sr_install_factory_config,
* clearing the running datastore, loading startup-config), letting the already-
* consistent sysrepo state drive a lightweight re-attach.
*/
#define SENTINEL_PATH "/run/confd.boot"
/* Callback type names from sysrepo plugin API */
#define SRP_INIT_CB "sr_plugin_init_cb"
#define SRP_CLEANUP_CB "sr_plugin_cleanup_cb"
@@ -64,6 +74,7 @@ struct plugin {
};
static sig_atomic_t pump_running = 1;
static int restart; /* set when sentinel found; suppresses conout() */
int debug = 0;
@@ -77,6 +88,9 @@ static void conout(int rc, const char *fmt, ...)
char buf[80];
va_list ap;
if (restart)
return;
snprintf(buf, sizeof(buf), sta, cr, col[rc], msg[rc], fmt);
va_start(ap, fmt);
vfprintf(stderr, buf, ap);
@@ -593,7 +607,7 @@ int main(int argc, char **argv)
struct plugin *plugins = NULL;
sr_conn_ctx_t *conn = NULL;
int log_level = LOG_ERR;
pid_t gen_pid, pump_pid;
pid_t gen_pid = -1, pump_pid = -1;
uint32_t timeout_s = 60;
int plugin_count = 0;
int fatal_fail = 0;
@@ -682,19 +696,30 @@ int main(int argc, char **argv)
if (load_plugins(&plugins, &plugin_count))
ERROR("load_plugins failed (continuing)");
/* Start gen-config in parallel — child is reaped before we need the result */
conout(3, "Generating factory-config and failure-config");
gen_pid = fork();
if (gen_pid < 0) {
ERRNO("Failed to fork gen-config");
conout(1, "\n");
goto cleanup;
}
if (gen_pid == 0)
_exit(systemf("/usr/libexec/confd/gen-config"));
/*
* Check for restart sentinel. If present, sysrepo and the system are
* already in a consistent state from a prior completed bootstrap — skip
* all destructive phases and re-attach to the live datastore instead.
*/
restart = fexist(SENTINEL_PATH);
if (restart)
NOTE("Restart sentinel found, skipping bootstrap and re-attaching to sysrepo");
/* Phase 1: Wipe stale SHM for a clean slate */
wipe_sysrepo_shm();
if (!restart) {
/* Start gen-config in parallel — child is reaped before we need the result */
conout(3, "Generating factory-config and failure-config");
gen_pid = fork();
if (gen_pid < 0) {
ERRNO("Failed to fork gen-config");
conout(1, "\n");
goto cleanup;
}
if (gen_pid == 0)
_exit(systemf("/usr/libexec/confd/gen-config"));
/* Phase 1: Wipe stale SHM for a clean slate */
wipe_sysrepo_shm();
}
/* Phase 2: Connect to sysrepo (rebuilds SHM from installed YANG modules) */
r = sr_connect(0, &conn);
@@ -703,25 +728,27 @@ int main(int argc, char **argv)
goto cleanup;
}
/* Phase 3: Wait for gen-config to finish */
waitpid(gen_pid, &status, 0);
if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
ERROR("gen-config failed (status=%d)", status);
conout(1, "\n");
goto cleanup;
}
conout(0, "\n");
if (!restart) {
/* Phase 3: Wait for gen-config to finish */
waitpid(gen_pid, &status, 0);
if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
ERROR("gen-config failed (status=%d)", status);
conout(1, "\n");
goto cleanup;
}
conout(0, "\n");
/* Phase 4: Install factory defaults into all datastores */
NOTE("Loading factory-default datastore from %s ...", factory_path);
conout(3, "Loading factory-default datastore");
r = sr_install_factory_config(conn, factory_path);
if (r != SR_ERR_OK) {
ERROR("sr_install_factory_config failed: %s", sr_strerror(r));
conout(1, "\n");
goto cleanup;
/* Phase 4: Install factory defaults into all datastores */
NOTE("Loading factory-default datastore from %s ...", factory_path);
conout(3, "Loading factory-default datastore");
r = sr_install_factory_config(conn, factory_path);
if (r != SR_ERR_OK) {
ERROR("sr_install_factory_config failed: %s", sr_strerror(r));
conout(1, "\n");
goto cleanup;
}
conout(0, "\n");
}
conout(0, "\n");
/* Phase 5: Start running-datastore session */
r = sr_session_start(conn, SR_DS_RUNNING, &sess);
@@ -730,19 +757,21 @@ int main(int argc, char **argv)
goto cleanup;
}
/* Phase 6: Clear running datastore so plugin init sees an empty
* tree. This matches the original bootstrap flow where running
* was cleared with '{}' before sysrepo-plugind started. When we
* later load startup-config, the diff will be all-create which is
* what the plugin callbacks expect. */
r = sr_replace_config(sess, NULL, NULL, timeout_ms);
if (r != SR_ERR_OK) {
ERROR("Failed to clear running datastore: %s", sr_strerror(r));
goto cleanup;
}
if (!restart) {
/* Phase 6: Clear running datastore so plugin init sees an empty
* tree. This matches the original bootstrap flow where running
* was cleared with '{}' before sysrepo-plugind started. When we
* later load startup-config, the diff will be all-create which is
* what the plugin callbacks expect. */
r = sr_replace_config(sess, NULL, NULL, timeout_ms);
if (r != SR_ERR_OK) {
ERROR("Failed to clear running datastore: %s", sr_strerror(r));
goto cleanup;
}
/* Enable test-mode YANG feature if needed */
maybe_enable_test_mode();
/* Enable test-mode YANG feature if needed */
maybe_enable_test_mode();
}
/* Phase 7: Initialize plugins (subscribe to YANG module changes) */
conout(3, "Loading confd plugins");
@@ -767,33 +796,35 @@ int main(int argc, char **argv)
plugins[i].get_subs(plugins[i].private_data, &plugins[i].sub, &plugins[i].fsub);
}
/* Phase 9: Fork event pump process for bootstrap.
* With SR_SUBSCR_NO_THREAD, sr_replace_config() blocks waiting
* for callbacks. The pump process processes those events. */
pump_pid = fork();
if (pump_pid < 0) {
ERRNO("Failed to fork event pump");
goto cleanup;
}
if (pump_pid == 0)
event_pump(plugins, plugin_count);
if (!restart) {
/* Phase 9: Fork event pump process for bootstrap.
* With SR_SUBSCR_NO_THREAD, sr_replace_config() blocks waiting
* for callbacks. The pump process processes those events. */
pump_pid = fork();
if (pump_pid < 0) {
ERRNO("Failed to fork event pump");
goto cleanup;
}
if (pump_pid == 0)
event_pump(plugins, plugin_count);
/* Phase 10: Load startup config -- plugins are now subscribed, so
* sr_replace_config() will trigger their change callbacks.
* The event pump process processes those callbacks. */
conout(3, "Loading startup-config");
if (bootstrap_config(conn, sess, factory_path, startup_path,
failure_path, test_path, timeout_ms)) {
/* Phase 10: Load startup config -- plugins are now subscribed, so
* sr_replace_config() will trigger their change callbacks.
* The event pump process processes those callbacks. */
conout(3, "Loading startup-config");
if (bootstrap_config(conn, sess, factory_path, startup_path,
failure_path, test_path, timeout_ms)) {
kill(pump_pid, SIGTERM);
waitpid(pump_pid, NULL, 0);
conout(1, "\n");
goto cleanup;
}
conout(0, "\n");
/* Phase 11: Stop event pump — bootstrap is done */
kill(pump_pid, SIGTERM);
waitpid(pump_pid, NULL, 0);
conout(1, "\n");
goto cleanup;
}
conout(0, "\n");
/* Phase 11: Stop event pump — bootstrap is done */
kill(pump_pid, SIGTERM);
waitpid(pump_pid, NULL, 0);
/* No more progress to show, go to quiet daemon mode */
quiet_now();
@@ -801,6 +832,21 @@ int main(int argc, char **argv)
/* Signal that bootstrap is complete (dbus, resolvconf depend on this) */
symlink("/run/finit/cond/reconf", "/run/finit/cond/usr/bootstrap");
/*
* Write restart sentinel. From this point on, sysrepo and the system
* are in a consistent state. If confd exits for any reason (crash or
* clean shutdown) and Finit restarts it, the sentinel tells it to skip
* the destructive bootstrap phases and re-attach to the live datastore.
* The sentinel lives in /run (tmpfs) so a real reboot always starts clean.
*/
{
int sfd = open(SENTINEL_PATH, O_CREAT | O_WRONLY | O_TRUNC, 0644);
if (sfd >= 0)
close(sfd);
else
WARN("Failed to write restart sentinel %s: %m", SENTINEL_PATH);
}
/* Phase 12: Steady-state — libev event loop */
{
struct ev_signal sigterm_w, sigint_w, sighup_w, sigquit_w;