Only start crond if there exist at least one schedule configured

package/confd/confd.mk

@@ -38,6 +38,8 @@ endif
 define CONFD_INSTALL_EXTRA
 	for fn in confd.conf crond.conf resolvconf.conf; do \
 		cp $(CONFD_PKGDIR)/$$fn  $(FINIT_D)/available/; \
+	done
+	for fn in confd.conf resolvconf.conf; do \
 		ln -sf ../available/$$fn $(FINIT_D)/enabled/$$fn; \
 	done
 	cp $(CONFD_PKGDIR)/tmpfiles.conf $(TARGET_DIR)/etc/tmpfiles.d/confd.conf

src/confd/src/schedule.c

@@ -11,7 +11,9 @@
 #include "core.h"
 
 #define XPATH_BASE    "/ietf-system:system/infix-schedule:schedules"
-#define CRONTAB_FILE  "/var/spool/cron/crontabs/admin"
+#define CRONTAB_DIR   "/var/spool/cron/crontabs"
+#define CRONTAB_FILE  CRONTAB_DIR "/admin"
+#define CRONTAB_NEXT  CRONTAB_DIR "/admin.next"
 
 /* Features register a consumer to run a command on a schedule. */
 static const struct cron_consumer **consumers;
@@ -176,11 +178,13 @@ static void build_cron_expr(struct lyd_node *recurrence, char *expr, size_t sz)
 	snprintf(expr, sz, "%s %s %s %s %s", min, hr, dom, mon, dow);
 }
 
-static void reload_crond(void)
+static void crond_apply(int active)
 {
-	char *args[] = { "pkill", "-HUP", "crond", NULL };
-
-	runbg(args, 0);
+	if (active) {
+		finit_enable("crond");
+	} else {
+		finit_disable("crond");
+	}
 }
 
 /*
@@ -217,21 +221,23 @@ static int schedule_to_cron(struct lyd_node *config, const char *name,
 }
 
 /*
- * Rebuild the crontab from every registered consumer.  Each consumer points
- * at a feature container holding a schedule-ref; we resolve that to cron
- * fields and emit one line running the consumer's own command.
+ * Generate the next crontab from every registered consumer.  Each consumer
+ * points at a feature container holding a schedule-ref; we resolve that to
+ * cron fields and emit one line running the consumer's own command.  Written
+ * to CRONTAB_NEXT, promoted in SR_EV_DONE.  Returns the active job count;
+ * CRONTAB_NEXT is removed when there are none, so DONE knows to stop crond.
  */
-static void apply_schedules(struct lyd_node *config)
+static int gen_schedules(struct lyd_node *config)
 {
 	int count = 0;
 	FILE *fp;
 	size_t i;
 
-	makepath("/var/spool/cron/crontabs");
-	fp = fopen(CRONTAB_FILE, "w");
+	makepath(CRONTAB_DIR);
+	fp = fopen(CRONTAB_NEXT, "w");
 	if (!fp) {
-		ERROR("schedule: failed to open %s", CRONTAB_FILE);
-		return;
+		ERROR("schedule: failed to open %s", CRONTAB_NEXT);
+		return -1;
 	}
 	fprintf(fp, "# Managed by infix-schedule\n");
 
@@ -267,16 +273,41 @@ static void apply_schedules(struct lyd_node *config)
 
 out:
 	fclose(fp);
-	reload_crond();
-	NOTE("schedule: %d active job(s) written to crontab", count);
+	if (!count)
+		(void)remove(CRONTAB_NEXT);
+
+	return count;
 }
 
 int schedule_change(sr_session_ctx_t *session, struct lyd_node *config,
 		    struct lyd_node *diff, sr_event_t event, struct confd *confd)
 {
-	if (event != SR_EV_DONE && event != SR_EV_ENABLED)
+	if (diff && !lydx_get_xpathf(diff, XPATH_BASE))
 		return SR_ERR_OK;
 
-	apply_schedules(config);
+	switch (event) {
+	case SR_EV_ENABLED:	/* first time, on register */
+	case SR_EV_CHANGE:	/* regular change */
+		gen_schedules(config);
+		break;
+
+	case SR_EV_ABORT:	/* user abort, or another plugin failed */
+		(void)remove(CRONTAB_NEXT);
+		break;
+
+	case SR_EV_DONE:
+		if (fexist(CRONTAB_NEXT)) {
+			(void)rename(CRONTAB_NEXT, CRONTAB_FILE);
+			crond_apply(1);
+		} else {
+			(void)remove(CRONTAB_FILE);
+			crond_apply(0);
+		}
+		break;
+
+	default:
+		break;
+	}
+
 	return SR_ERR_OK;
 }