northd: Allow delay of northd engine runs

Add config option called "northd-backoff-interval-ms" that allows to delay northd engine runs capped by the config option. When the config option is set to 0 or unspecified, the engine will run without any restrictions. If the value >0 we will delay northd engine run by the previous run time capped by the config option. Signed-off-by: Ales Musil <amusil@redhat.com>
almusil · Aug 8, 2023 · 4244808 · 4244808
1 parent d1d6975
commit 4244808
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Showing 5 changed files with 41 additions and 4 deletions.
diff --git a/NEWS b/NEWS
@@ -10,6 +10,8 @@ Post v23.06.0
   - To allow optimizing ovn-controller's monitor conditions for the regular
     VIF case, ovn-controller now unconditionally monitors all sub-ports
     (ports with parent_port set).
+  - Add "northd-backoff-interval-ms" config option to delay northd engine
+    runs capped at the set value.
 
 OVN v23.06.0 - 01 Jun 2023
 --------------------------

diff --git a/northd/inc-proc-northd.c b/northd/inc-proc-northd.c
@@ -42,6 +42,8 @@ VLOG_DEFINE_THIS_MODULE(inc_proc_northd);
 
 static unixctl_cb_func chassis_features_list;
 
+static int64_t next_northd_run_ms = 0;
+
 #define NB_NODES \
     NB_NODE(nb_global, "nb_global") \
     NB_NODE(logical_switch, "logical_switch") \
@@ -295,8 +297,10 @@ void inc_proc_northd_init(struct ovsdb_idl_loop *nb,
 /* Returns true if the incremental processing ended up updating nodes. */
 bool inc_proc_northd_run(struct ovsdb_idl_txn *ovnnb_txn,
                          struct ovsdb_idl_txn *ovnsb_txn,
-                         bool recompute) {
+                         bool recompute, uint32_t backoff_ms) {
     ovs_assert(ovnnb_txn && ovnsb_txn);
+
+    int64_t start = time_msec();
     engine_init_run();
 
     /* Force a full recompute if instructed to, for example, after a NB/SB
@@ -330,6 +334,12 @@ bool inc_proc_northd_run(struct ovsdb_idl_txn *ovnnb_txn,
     } else {
         engine_set_force_recompute(false);
     }
+
+    int64_t now = time_msec();
+    /* Postpone the next run by length of current run with maximum capped
+     * by "northd-backoff-interval-ms" interval. */
+    next_northd_run_ms = now + MIN(now - start, backoff_ms);
+
     return engine_has_updated();
 }
 
@@ -339,6 +349,17 @@ void inc_proc_northd_cleanup(void)
     engine_set_context(NULL);
 }
 
+bool
+inc_proc_northd_can_run(bool recompute)
+{
+    if (recompute || time_msec() >= next_northd_run_ms) {
+        return true;
+    }
+
+    poll_timer_wait_until(next_northd_run_ms);
+    return false;
+}
+
 static void
 chassis_features_list(struct unixctl_conn *conn, int argc OVS_UNUSED,
                       const char *argv[] OVS_UNUSED, void *features_)

diff --git a/northd/inc-proc-northd.h b/northd/inc-proc-northd.h
@@ -10,7 +10,8 @@ void inc_proc_northd_init(struct ovsdb_idl_loop *nb,
                           struct ovsdb_idl_loop *sb);
 bool inc_proc_northd_run(struct ovsdb_idl_txn *ovnnb_txn,
                          struct ovsdb_idl_txn *ovnsb_txn,
-                         bool recompute);
+                         bool recompute, uint32_t backoff_ms);
 void inc_proc_northd_cleanup(void);
+bool inc_proc_northd_can_run(bool recompute);
 
 #endif /* INC_PROC_NORTHD */
diff --git a/northd/ovn-northd.c b/northd/ovn-northd.c
@@ -868,6 +868,7 @@ main(int argc, char *argv[])
     /* Main loop. */
     exiting = false;
 
+    uint32_t northd_backoff_ms = 0;
     bool recompute = false;
     while (!exiting) {
         update_ssl_config();
@@ -932,10 +933,12 @@ main(int argc, char *argv[])
 
             if (ovsdb_idl_has_lock(ovnsb_idl_loop.idl)) {
                 bool activity = false;
-                if (ovnnb_txn && ovnsb_txn) {
+                if (ovnnb_txn && ovnsb_txn &&
+                    inc_proc_northd_can_run(recompute)) {
                     int64_t loop_start_time = time_wall_msec();
                     activity = inc_proc_northd_run(ovnnb_txn, ovnsb_txn,
-                                                        recompute);
+                                                   recompute,
+                                                   northd_backoff_ms);
                     recompute = false;
                     check_and_add_supported_dhcp_opts_to_sb_db(
                                  ovnsb_txn, ovnsb_idl_loop.idl);
@@ -1019,6 +1022,9 @@ main(int argc, char *argv[])
         if (nb) {
             interval = smap_get_int(&nb->options, "northd_probe_interval",
                                     interval);
+            northd_backoff_ms = smap_get_uint(&nb->options,
+                                              "northd-backoff-interval-ms",
+                                              200);
         }
         set_idl_probe_interval(ovnnb_idl_loop.idl, ovnnb_db, interval);
         set_idl_probe_interval(ovnsb_idl_loop.idl, ovnsb_db, interval);

diff --git a/ovn-nb.xml b/ovn-nb.xml
@@ -349,6 +349,13 @@
         of HWOL compatibility with GDP.
       </column>
 
+      <column name="options" key="northd-backoff-interval-ms">
+        Maximum interval that the northd incremental engine is delayed by
+        in milliseconds. Setting the value to nonzero delays the next northd
+        engine run by the previous run time, capped by the specified value.
+        If the value is zero the engine won't be delayed at all.
+      </column>
+
       <group title="Options for configuring interconnection route advertisement">
         <p>
           These options control how routes are advertised between OVN