ovn: Add '--restart' flag to ovn-controller exit.

When "--restart" is passed to ovn-controller's exit command, then
database entries are not removed for this hypervisor. This means that
* Encaps
* Chassis
* OVS ports
are not removed.

The reasoning is that if the intent is to restart ovn-controller, this
will allow for tunnels to remain up and allow for traffic not to be
interrupted during the restart. When ovn-controller is started again, it
picks back up from where it was.

Signed-off-by: Mark Michelson <mmichels@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

controller/ovn-controller.c

@@ -544,11 +544,18 @@ ctrl_register_ovs_idl(struct ovsdb_idl *ovs_idl)
     physical_register_ovs_idl(ovs_idl);
 }
 
+struct ovn_controller_exit_args {
+    bool *exiting;
+    bool *restart;
+};
+
 int
 main(int argc, char *argv[])
 {
     struct unixctl_server *unixctl;
     bool exiting;
+    bool restart;
+    struct ovn_controller_exit_args exit_args = {&exiting, &restart};
     int retval;
 
     ovs_cmdl_proctitle_init(argc, argv);
@@ -563,7 +570,8 @@ main(int argc, char *argv[])
     if (retval) {
         exit(EXIT_FAILURE);
     }
-    unixctl_command_register("exit", "", 0, 0, ovn_controller_exit, &exiting);
+    unixctl_command_register("exit", "", 0, 1, ovn_controller_exit,
+                             &exit_args);
 
     /* Initialize group ids for loadbalancing. */
     struct ovn_extend_table group_table;
@@ -641,6 +649,7 @@ main(int argc, char *argv[])
     stopwatch_create(CONTROLLER_LOOP_STOPWATCH_NAME, SW_MS);
     /* Main loop. */
     exiting = false;
+    restart = false;
     while (!exiting) {
         /* Check OVN SB database. */
         char *new_ovnsb_remote = get_ovnsb_remote(ovs_idl_loop.idl);
@@ -859,42 +868,45 @@ main(int argc, char *argv[])
         }
     }
 
-    /* It's time to exit.  Clean up the databases. */
-    bool done = false;
-    while (!done) {
-        struct ovsdb_idl_txn *ovs_idl_txn = ovsdb_idl_loop_run(&ovs_idl_loop);
-        struct ovsdb_idl_txn *ovnsb_idl_txn
-            = ovsdb_idl_loop_run(&ovnsb_idl_loop);
+    /* It's time to exit.  Clean up the databases if we are not restarting */
+    if (!restart) {
+        bool done = false;
+        while (!done) {
+            struct ovsdb_idl_txn *ovs_idl_txn
+                = ovsdb_idl_loop_run(&ovs_idl_loop);
+            struct ovsdb_idl_txn *ovnsb_idl_txn
+                = ovsdb_idl_loop_run(&ovnsb_idl_loop);
+
+            const struct ovsrec_bridge_table *bridge_table
+                = ovsrec_bridge_table_get(ovs_idl_loop.idl);
+            const struct ovsrec_open_vswitch_table *ovs_table
+                = ovsrec_open_vswitch_table_get(ovs_idl_loop.idl);
+
+            const struct sbrec_port_binding_table *port_binding_table
+                = sbrec_port_binding_table_get(ovnsb_idl_loop.idl);
+
+            const struct ovsrec_bridge *br_int = get_br_int(ovs_idl_txn,
+                                                            bridge_table,
+                                                            ovs_table);
+            const char *chassis_id = get_chassis_id(ovs_table);
+            const struct sbrec_chassis *chassis
+                = (chassis_id
+                   ? chassis_lookup_by_name(sbrec_chassis_by_name, chassis_id)
+                   : NULL);
+
+            /* Run all of the cleanup functions, even if one of them returns
+             * false. We're done if all of them return true. */
+            done = binding_cleanup(ovnsb_idl_txn, port_binding_table, chassis);
+            done = chassis_cleanup(ovnsb_idl_txn, chassis) && done;
+            done = encaps_cleanup(ovs_idl_txn, br_int) && done;
+            if (done) {
+                poll_immediate_wake();
+            }
 
-        const struct ovsrec_bridge_table *bridge_table
-            = ovsrec_bridge_table_get(ovs_idl_loop.idl);
-        const struct ovsrec_open_vswitch_table *ovs_table
-            = ovsrec_open_vswitch_table_get(ovs_idl_loop.idl);
-
-        const struct sbrec_port_binding_table *port_binding_table
-            = sbrec_port_binding_table_get(ovnsb_idl_loop.idl);
-
-        const struct ovsrec_bridge *br_int = get_br_int(ovs_idl_txn,
-                                                        bridge_table,
-                                                        ovs_table);
-        const char *chassis_id = get_chassis_id(ovs_table);
-        const struct sbrec_chassis *chassis
-            = (chassis_id
-               ? chassis_lookup_by_name(sbrec_chassis_by_name, chassis_id)
-               : NULL);
-
-        /* Run all of the cleanup functions, even if one of them returns false.
-         * We're done if all of them return true. */
-        done = binding_cleanup(ovnsb_idl_txn, port_binding_table, chassis);
-        done = chassis_cleanup(ovnsb_idl_txn, chassis) && done;
-        done = encaps_cleanup(ovs_idl_txn, br_int) && done;
-        if (done) {
-            poll_immediate_wake();
+            ovsdb_idl_loop_commit_and_wait(&ovnsb_idl_loop);
+            ovsdb_idl_loop_commit_and_wait(&ovs_idl_loop);
+            poll_block();
         }
-
-        ovsdb_idl_loop_commit_and_wait(&ovnsb_idl_loop);
-        ovsdb_idl_loop_commit_and_wait(&ovs_idl_loop);
-        poll_block();
     }
 
     unixctl_server_destroy(unixctl);
@@ -1010,12 +1022,12 @@ usage(void)
 }
 
 static void
-ovn_controller_exit(struct unixctl_conn *conn, int argc OVS_UNUSED,
-             const char *argv[] OVS_UNUSED, void *exiting_)
+ovn_controller_exit(struct unixctl_conn *conn, int argc,
+             const char *argv[], void *exit_args_)
 {
-    bool *exiting = exiting_;
-    *exiting = true;
-
+    struct ovn_controller_exit_args *exit_args = exit_args_;
+    *exit_args->exiting = true;
+    *exit_args->restart = argc == 2 && !strcmp(argv[1], "--restart");
     unixctl_command_reply(conn, NULL);
 }