Restart services with a delay in case they are restarted too often

In case a service is restarted while the DP is not ready yet, it gets
restarted again immediatelly, which means the DP might still not be
ready. The allowed number of restarts is then depleted quickly.

This patch changes the restart mechanism such that the first restart
happens immediatelly, the second is scheduled after 2 second, then 4
etc..

https://fedorahosted.org/sssd/ticket/1528

1 files changed, 59 insertions, 14 deletions

diff --git a/src/monitor/monitor.c b/src/monitor/monitor.c
index 5293a3453..7be8e5093 100644
--- a/src/monitor/monitor.c
+++ b/src/monitor/monitor.c
@@ -60,6 +60,19 @@
  * monitor will get crazy hammering children with messages */
 #define MONITOR_DEF_PING_TIME 10
 
+/* TODO: get the restart related values from config */
+#define MONITOR_RESTART_CNT_INTERVAL_RESET   30
+/* maximum allowed number of service restarts if the restarts
+ * were less than MONITOR_RESTART_CNT_INTERVAL_RESET apart, which would
+ * indicate a crash after startup or after every request */
+#define MONITOR_MAX_SVC_RESTARTS    2
+/* The services are restarted with a delay in case the restart was
+ * hitting a race condition where the DP is not ready yet either.
+ * The MONITOR_MAX_RESTART_DELAY defines the maximum delay between
+ * restarts.
+ */
+#define MONITOR_MAX_RESTART_DELAY   4
+
 /* Special value to leave the Kerberos Replay Cache set to use
  * the libkrb5 defaults
  */
@@ -2304,10 +2317,43 @@ static void service_startup_handler(struct tevent_context *ev,
     _exit(1);
 }
 
+static void mt_svc_restart(struct tevent_context *ev,
+                           struct tevent_timer *te,
+                           struct timeval t, void *ptr)
+{
+    struct mt_svc *svc;
+
+    svc = talloc_get_type(ptr, struct mt_svc);
+    if (svc == NULL) {
+        return;
+    }
+
+    DEBUG(SSSDBG_TRACE_FUNC, ("Scheduling service %s for restart %d\n",
+                              svc->name, svc->restarts+1));
+
+    if (svc->type == MT_SVC_SERVICE) {
+        add_new_service(svc->mt_ctx, svc->name, svc->restarts + 1);
+    } else if (svc->type == MT_SVC_PROVIDER) {
+        add_new_provider(svc->mt_ctx, svc->name, svc->restarts + 1);
+    } else {
+        /* Invalid type? */
+        DEBUG(SSSDBG_CRIT_FAILURE,
+              ("BUG: Invalid child process type [%d]\n", svc->type));
+    }
+
+    /* Free the old service (which will also remove it
+     * from the child list)
+     */
+    talloc_free(svc);
+}
+
 static void mt_svc_exit_handler(int pid, int wait_status, void *pvt)
 {
     struct mt_svc *svc = talloc_get_type(pvt, struct mt_svc);
     time_t now = time(NULL);
+    struct tevent_timer *te;
+    struct timeval tv;
+    int restart_delay;
 
     if WIFEXITED(wait_status) {
         DEBUG(SSSDBG_OP_FAILURE,
@@ -2328,32 +2374,31 @@ static void mt_svc_exit_handler(int pid, int wait_status, void *pvt)
         return;
     }
 
-    if ((now - svc->last_restart) > 30) { /* TODO: get val from config */
+    if ((now - svc->last_restart) > MONITOR_RESTART_CNT_INTERVAL_RESET) {
         svc->restarts = 0;
     }
 
     /* Restart the service */
-    if (svc->restarts > 2) { /* TODO: get val from config */
+    if (svc->restarts > MONITOR_MAX_SVC_RESTARTS) {
         DEBUG(SSSDBG_FATAL_FAILURE,
               ("Process [%s], definitely stopped!\n", svc->name));
         talloc_free(svc);
         return;
     }
 
-    if (svc->type == MT_SVC_SERVICE) {
-        add_new_service(svc->mt_ctx, svc->name, svc->restarts + 1);
-    } else if (svc->type == MT_SVC_PROVIDER) {
-        add_new_provider(svc->mt_ctx, svc->name, svc->restarts + 1);
-    } else {
-        /* Invalid type? */
-        DEBUG(SSSDBG_CRIT_FAILURE,
-              ("BUG: Invalid child process type [%d]\n", svc->type));
+    /* restarts are schedule after 0, 2, 4 seconds */
+    restart_delay = svc->restarts << 1;
+    if (restart_delay > MONITOR_MAX_RESTART_DELAY) {
+        restart_delay = MONITOR_MAX_RESTART_DELAY;
     }
 
-    /* Free the old service (which will also remove it
-     * from the child list)
-     */
-    talloc_free(svc);
+    tv = tevent_timeval_current_ofs(restart_delay, 0);
+    te = tevent_add_timer(svc->mt_ctx->ev, svc, tv, mt_svc_restart, svc);
+    if (!te) {
+        /* Nothing much we can do */
+        DEBUG(SSSDBG_CRIT_FAILURE, ("Out of memory?!\n"));
+        return;
+    }
 }
 
 int main(int argc, const char *argv[])