From: Lucas Alvares Gomes <[email protected]>

NOTE: SENDING THIS PATCH AS A RFC TO SEE WHAT OTHERS MIGHT THINK ABOUT
THE IDEA PRIOR TO WRITTING TESTS TO IT.

CMSes integrating with OVN often uses the nb_cfg mechanism as a way to
check the health status of the ovn-controller process but, the current
implementation isn't ideal for that purpose because it floods the control
plane with update notifications every time the nb_cfg value is
incremented.

This patch is merging two ideas:

1) Han Zhou proposed a patch [0] creating a table called Chassis_Private
   where each hypervisor *only* writes and monitors its own record to
   avoid this flooding problem.

2) Having ovn-controller to periodically log that it's alive instead of
   relying on the nb_cfg mechanism.

By using this mechanism, a CMS can more easily just read this new
Chassis_Private table and figure out the status of each Chassis
(ovn-controller) in the cluster.

Here's some reasons why I believe this approach is better than having
to bump the  nb_cfg value:

1) Simple integration. Before, the CMS had to increment the nb_cfg
   value in the NB_Global table and wait for it to be propagated to the
   Southbound database (ovn-northd and then ovn-controllers) Chassis
   table in order to know the status of the Chassis.

   Now, it can just read the Chassis_Private table and compare the
   alive_at column against the current time.

2) Less costy. Just one read from the db is needed, no writing. Code
   using the nb_cfg mechanism had to implement a few safe-guard code to
   make less error prone. See [1] and [2] for example.

3) Backwards compatibility. The patch [0] was moving the nb_cfg value
   to new table so, systems relying on it would need to update their
   code upon updating OVN.

To enable this new mechanism set an option called
chassis_liveness_interval=N to the "options" column in the NB_Global
table, where N is the time (in seconds) in which the ovn-controller
should updates the alive_at column. If not set or set to 0, the
mechanism is disabled. By default, it's disabled.

[0] https://patchwork.ozlabs.org/patch/899608/
[1] https://review.opendev.org/#/c/703612/
[2] https://review.opendev.org/#/c/704530/

Co-authored-by: Han Zhou <[email protected]>
Co-authored-by: Numan Siddique <[email protected]>
Co-authored-by: Dumitru Ceara <[email protected]>
Signed-off-by: Lucas Alvares Gomes <[email protected]>
---
 controller/chassis.c        | 56 +++++++++++++++++++++++++++++++++++--
 controller/chassis.h        | 11 ++++++--
 controller/ovn-controller.c | 44 +++++++++++++++++++++++++++--
 lib/chassis-index.c         | 26 +++++++++++++++++
 lib/chassis-index.h         |  5 ++++
 northd/ovn-northd.c         |  4 +++
 ovn-sb.ovsschema            | 13 +++++++--
 ovn-sb.xml                  | 35 +++++++++++++++++++++++
 8 files changed, 185 insertions(+), 9 deletions(-)

diff --git a/controller/chassis.c b/controller/chassis.c
index 522893ead..7892cb966 100644
--- a/controller/chassis.c
+++ b/controller/chassis.c
@@ -24,6 +24,7 @@
 #include "openvswitch/dynamic-string.h"
 #include "openvswitch/vlog.h"
 #include "openvswitch/ofp-parse.h"
+#include "openvswitch/poll-loop.h"
 #include "lib/chassis-index.h"
 #include "lib/ovn-sb-idl.h"
 #include "ovn-controller.h"
@@ -47,11 +48,16 @@ struct chassis_info {
 
     /* True if Chassis SB record is initialized, false otherwise. */
     uint32_t id_inited : 1;
+
+    /* Next livennes update time to update the 'alive_at' column of
+     * Chassis_Private table. */
+    long long int next_liveness_update;
 };
 
 static struct chassis_info chassis_state = {
     .id = DS_EMPTY_INITIALIZER,
     .id_inited = false,
+    .next_liveness_update = LLONG_MAX,
 };
 
 static void
@@ -581,18 +587,38 @@ chassis_update(const struct sbrec_chassis *chassis_rec,
     free(encaps);
 }
 
+static void
+chassis_update_liveness_cfg(const struct sbrec_chassis_private *chassis_rec,
+                            struct chassis_info *ch_info,
+                            int chassis_liveness_interval)
+{
+    if (ch_info->next_liveness_update == LLONG_MAX ||
+        time_msec() > ch_info->next_liveness_update) {
+        sbrec_chassis_private_set_alive_at(
+            chassis_rec,
+            xastrftime_msec("%Y-%m-%d %H:%M:%S", time_wall_msec(), true));
+        ch_info->next_liveness_update =
+            time_msec() + chassis_liveness_interval * 1000;
+    }
+}
+
 /* Returns this chassis's Chassis record, if it is available. */
 const struct sbrec_chassis *
 chassis_run(struct ovsdb_idl_txn *ovnsb_idl_txn,
             struct ovsdb_idl_index *sbrec_chassis_by_name,
+            struct ovsdb_idl_index *sbrec_chassis_private_by_name,
             const struct ovsrec_open_vswitch_table *ovs_table,
             const struct sbrec_chassis_table *chassis_table,
             const char *chassis_id,
             const struct ovsrec_bridge *br_int,
-            const struct sset *transport_zones)
+            const struct sset *transport_zones,
+            const struct sbrec_chassis_private **chassis_private,
+            int chassis_liveness_interval)
 {
     struct ovs_chassis_cfg ovs_cfg;
 
+    *chassis_private = NULL;
+
     /* Get the chassis config from the ovs table. */
     ovs_chassis_cfg_init(&ovs_cfg);
     if (!chassis_parse_ovs_config(ovs_table, br_int, &ovs_cfg)) {
@@ -616,6 +642,24 @@ chassis_run(struct ovsdb_idl_txn *ovnsb_idl_txn,
                                   chassis_id);
     }
 
+    /* Create the Chassis_Private entry if it's not there yet */
+    const struct sbrec_chassis_private *chassis_private_rec =
+        chassis_private_lookup_by_name(sbrec_chassis_private_by_name,
+                                       chassis_id);
+    if (!chassis_private_rec && ovnsb_idl_txn) {
+        chassis_private_rec = sbrec_chassis_private_insert(ovnsb_idl_txn);
+        sbrec_chassis_private_set_name(chassis_private_rec, chassis_id);
+    }
+
+    /* Update the alive_at column from the Chassis_Private table if
+     * the chassis liveness mechanism is enabled */
+    if (chassis_private_rec && ovnsb_idl_txn && chassis_liveness_interval) {
+        chassis_update_liveness_cfg(chassis_private_rec, &chassis_state,
+                                    chassis_liveness_interval);
+    }
+
+    *chassis_private = chassis_private_rec;
+
     ovs_chassis_cfg_destroy(&ovs_cfg);
     return chassis_rec;
 }
@@ -669,7 +713,8 @@ chassis_get_mac(const struct sbrec_chassis *chassis_rec,
  * required. */
 bool
 chassis_cleanup(struct ovsdb_idl_txn *ovnsb_idl_txn,
-                const struct sbrec_chassis *chassis_rec)
+                const struct sbrec_chassis *chassis_rec,
+                const struct sbrec_chassis_private *chassis_private_rec)
 {
     if (!chassis_rec) {
         return true;
@@ -679,6 +724,7 @@ chassis_cleanup(struct ovsdb_idl_txn *ovnsb_idl_txn,
                                   "ovn-controller: unregistering chassis '%s'",
                                   chassis_rec->name);
         sbrec_chassis_delete(chassis_rec);
+        sbrec_chassis_private_delete(chassis_private_rec);
     }
     return false;
 }
@@ -695,3 +741,9 @@ chassis_get_id(void)
 
     return NULL;
 }
+
+void chassis_wait(int chassis_liveness_interval) {
+    if (chassis_liveness_interval) {
+        poll_timer_wait_until(chassis_state.next_liveness_update);
+    }
+}
diff --git a/controller/chassis.h b/controller/chassis.h
index 178d2957e..38a549553 100644
--- a/controller/chassis.h
+++ b/controller/chassis.h
@@ -17,6 +17,7 @@
 #define OVN_CHASSIS_H 1
 
 #include <stdbool.h>
+#include "lib/ovn-sb-idl.h"
 
 struct ovsdb_idl;
 struct ovsdb_idl_index;
@@ -33,17 +34,21 @@ void chassis_register_ovs_idl(struct ovsdb_idl *);
 const struct sbrec_chassis *chassis_run(
     struct ovsdb_idl_txn *ovnsb_idl_txn,
     struct ovsdb_idl_index *sbrec_chassis_by_name,
+    struct ovsdb_idl_index *sbrec_chassis_private_by_name,
     const struct ovsrec_open_vswitch_table *,
     const struct sbrec_chassis_table *,
     const char *chassis_id, const struct ovsrec_bridge *br_int,
-    const struct sset *transport_zones);
+    const struct sset *transport_zones,
+    const struct sbrec_chassis_private **chassis_private,
+    int chassis_liveness_interval);
 bool chassis_cleanup(struct ovsdb_idl_txn *ovnsb_idl_txn,
-                     const struct sbrec_chassis *);
+                     const struct sbrec_chassis *,
+                     const struct sbrec_chassis_private *);
 bool chassis_get_mac(const struct sbrec_chassis *chassis,
                      const char *bridge_mapping,
                      struct eth_addr *chassis_mac);
 const char *chassis_get_id(void);
 const char * get_chassis_mac_mappings(const struct smap *ext_ids);
-
+void chassis_wait(int chassis_liveness_interval);
 
 #endif /* controller/chassis.h */
diff --git a/controller/ovn-controller.c b/controller/ovn-controller.c
index 4d245ca28..fd9d95da2 100644
--- a/controller/ovn-controller.c
+++ b/controller/ovn-controller.c
@@ -155,6 +155,7 @@ update_sb_monitors(struct ovsdb_idl *ovnsb_idl,
     struct ovsdb_idl_condition ce =  OVSDB_IDL_CONDITION_INIT(&ce);
     struct ovsdb_idl_condition ip_mcast = OVSDB_IDL_CONDITION_INIT(&ip_mcast);
     struct ovsdb_idl_condition igmp = OVSDB_IDL_CONDITION_INIT(&igmp);
+    struct ovsdb_idl_condition chprv = OVSDB_IDL_CONDITION_INIT(&chprv);
 
     if (monitor_all) {
         ovsdb_idl_condition_add_clause_true(&pb);
@@ -165,6 +166,7 @@ update_sb_monitors(struct ovsdb_idl *ovnsb_idl,
         ovsdb_idl_condition_add_clause_true(&ce);
         ovsdb_idl_condition_add_clause_true(&ip_mcast);
         ovsdb_idl_condition_add_clause_true(&igmp);
+        ovsdb_idl_condition_add_clause_true(&chprv);
         goto out;
     }
 
@@ -196,6 +198,10 @@ update_sb_monitors(struct ovsdb_idl *ovnsb_idl,
                                                   &chassis->header_.uuid);
         sbrec_igmp_group_add_clause_chassis(&igmp, OVSDB_F_EQ,
                                             &chassis->header_.uuid);
+
+        /* Monitors Chassis_Private record for current chassis only */
+        sbrec_chassis_private_add_clause_name(&chprv, OVSDB_F_EQ,
+                                              chassis->name);
     }
     if (local_ifaces) {
         const char *name;
@@ -229,6 +235,7 @@ out:
     sbrec_controller_event_set_condition(ovnsb_idl, &ce);
     sbrec_ip_multicast_set_condition(ovnsb_idl, &ip_mcast);
     sbrec_igmp_group_set_condition(ovnsb_idl, &igmp);
+    sbrec_chassis_private_set_condition(ovnsb_idl, &chprv);
     ovsdb_idl_condition_destroy(&pb);
     ovsdb_idl_condition_destroy(&lf);
     ovsdb_idl_condition_destroy(&mb);
@@ -237,6 +244,7 @@ out:
     ovsdb_idl_condition_destroy(&ce);
     ovsdb_idl_condition_destroy(&ip_mcast);
     ovsdb_idl_condition_destroy(&igmp);
+    ovsdb_idl_condition_destroy(&chprv);
 }
 
 static const char *
@@ -687,6 +695,15 @@ get_transport_zones(const struct ovsrec_open_vswitch_table 
*ovs_table)
     return smap_get_def(&cfg->external_ids, "ovn-transport-zones", "");
 }
 
+static uint16_t
+get_chassis_liveness_interval(const struct sbrec_sb_global_table
+                              *sb_global_table)
+{
+    const struct sbrec_sb_global *sb
+        = sbrec_sb_global_table_first(sb_global_table);
+    return atoi(smap_get_def(&sb->options, "chassis_liveness_interval", "0"));
+}
+
 static void
 ctrl_register_ovs_idl(struct ovsdb_idl *ovs_idl)
 {
@@ -1760,6 +1777,8 @@ main(int argc, char *argv[])
 
     struct ovsdb_idl_index *sbrec_chassis_by_name
         = chassis_index_create(ovnsb_idl_loop.idl);
+    struct ovsdb_idl_index *sbrec_chassis_private_by_name
+        = chassis_private_index_create(ovnsb_idl_loop.idl);
     struct ovsdb_idl_index *sbrec_multicast_group_by_name_datapath
         = mcast_group_index_create(ovnsb_idl_loop.idl);
     struct ovsdb_idl_index *sbrec_port_binding_by_name
@@ -1821,6 +1840,10 @@ main(int argc, char *argv[])
     ovsdb_idl_omit(ovnsb_idl_loop.idl, &sbrec_connection_col_status);
     ovsdb_idl_omit(ovnsb_idl_loop.idl, &sbrec_connection_col_target);
 
+    /* Do not monitor the Chassis_Private external_ids column */
+    ovsdb_idl_omit(ovnsb_idl_loop.idl,
+                   &sbrec_chassis_private_col_external_ids);
+
     update_sb_monitors(ovnsb_idl_loop.idl, NULL, NULL, NULL, false);
 
     stopwatch_create(CONTROLLER_LOOP_STOPWATCH_NAME, SW_MS);
@@ -1998,10 +2021,16 @@ main(int argc, char *argv[])
                 process_br_int(ovs_idl_txn, bridge_table, ovs_table);
             const char *chassis_id = get_ovs_chassis_id(ovs_table);
             const struct sbrec_chassis *chassis = NULL;
+            const struct sbrec_chassis_private *chassis_private = NULL;
+            uint16_t chassis_liveness_interval = get_chassis_liveness_interval(
+                sbrec_sb_global_table_get(ovnsb_idl_loop.idl));
             if (chassis_id) {
                 chassis = chassis_run(ovnsb_idl_txn, sbrec_chassis_by_name,
+                                      sbrec_chassis_private_by_name,
                                       ovs_table, chassis_table, chassis_id,
-                                      br_int, &transport_zones);
+                                      br_int, &transport_zones,
+                                      &chassis_private,
+                                      chassis_liveness_interval);
             }
 
             if (br_int) {
@@ -2164,6 +2193,10 @@ main(int argc, char *argv[])
                 ofctrl_wait();
                 pinctrl_wait(ovnsb_idl_txn);
             }
+
+            if (chassis) {
+                chassis_wait(chassis_liveness_interval);
+            }
         }
 
         unixctl_server_run(unixctl);
@@ -2232,10 +2265,17 @@ main(int argc, char *argv[])
                    ? chassis_lookup_by_name(sbrec_chassis_by_name, chassis_id)
                    : NULL);
 
+            const struct sbrec_chassis_private *chassis_private
+                = (chassis_id
+                   ? chassis_private_lookup_by_name(
+                       sbrec_chassis_private_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 = chassis_cleanup(ovnsb_idl_txn, chassis,
+                                   chassis_private) && done;
             done = encaps_cleanup(ovs_idl_txn, br_int) && done;
             done = igmp_group_cleanup(ovnsb_idl_txn, sbrec_igmp_group) && done;
             if (done) {
diff --git a/lib/chassis-index.c b/lib/chassis-index.c
index 39066f4cc..d9bbba8e4 100644
--- a/lib/chassis-index.c
+++ b/lib/chassis-index.c
@@ -40,6 +40,32 @@ chassis_lookup_by_name(struct ovsdb_idl_index 
*sbrec_chassis_by_name,
     return retval;
 }
 
+struct ovsdb_idl_index *
+chassis_private_index_create(struct ovsdb_idl *idl)
+{
+    return ovsdb_idl_index_create1(
+        idl, &sbrec_chassis_private_col_name);
+}
+
+/* Finds and returns the chassis with the given 'name', or NULL if no such
+ * chassis exists. */
+const struct sbrec_chassis_private *
+chassis_private_lookup_by_name(
+    struct ovsdb_idl_index *sbrec_chassis_private_by_name,
+    const char *name)
+{
+    struct sbrec_chassis_private *target = \
+        sbrec_chassis_private_index_init_row(sbrec_chassis_private_by_name);
+    sbrec_chassis_private_index_set_name(target, name);
+
+    struct sbrec_chassis_private *retval = sbrec_chassis_private_index_find(
+        sbrec_chassis_private_by_name, target);
+
+    sbrec_chassis_private_index_destroy_row(target);
+
+    return retval;
+}
+
 struct ovsdb_idl_index *
 ha_chassis_group_index_create(struct ovsdb_idl *idl)
 {
diff --git a/lib/chassis-index.h b/lib/chassis-index.h
index 302e5f0fd..77d2e1f99 100644
--- a/lib/chassis-index.h
+++ b/lib/chassis-index.h
@@ -23,6 +23,11 @@ struct ovsdb_idl_index *chassis_index_create(struct 
ovsdb_idl *);
 const struct sbrec_chassis *chassis_lookup_by_name(
     struct ovsdb_idl_index *sbrec_chassis_by_name, const char *name);
 
+struct ovsdb_idl_index *chassis_private_index_create(struct ovsdb_idl *);
+
+const struct sbrec_chassis_private *chassis_private_lookup_by_name(
+    struct ovsdb_idl_index *sbrec_chassis_private_by_name, const char *name);
+
 struct ovsdb_idl_index *ha_chassis_group_index_create(struct ovsdb_idl *idl);
 const struct sbrec_ha_chassis_group *ha_chassis_group_lookup_by_name(
     struct ovsdb_idl_index *sbrec_ha_chassis_grp_by_name, const char *name);
diff --git a/northd/ovn-northd.c b/northd/ovn-northd.c
index 2580b4ec9..1b16f5ef6 100644
--- a/northd/ovn-northd.c
+++ b/northd/ovn-northd.c
@@ -11555,6 +11555,10 @@ main(int argc, char *argv[])
     ovsdb_idl_add_column(ovnsb_idl_loop.idl, &sbrec_chassis_col_name);
     ovsdb_idl_add_column(ovnsb_idl_loop.idl, &sbrec_chassis_col_external_ids);
 
+    ovsdb_idl_add_table(ovnsb_idl_loop.idl, &sbrec_table_chassis_private);
+    add_column_noalert(ovnsb_idl_loop.idl,
+                       &sbrec_chassis_private_col_external_ids);
+
     ovsdb_idl_add_table(ovnsb_idl_loop.idl, &sbrec_table_ha_chassis);
     add_column_noalert(ovnsb_idl_loop.idl,
                        &sbrec_ha_chassis_col_chassis);
diff --git a/ovn-sb.ovsschema b/ovn-sb.ovsschema
index d89f8dbbb..88da05849 100644
--- a/ovn-sb.ovsschema
+++ b/ovn-sb.ovsschema
@@ -1,7 +1,7 @@
 {
     "name": "OVN_Southbound",
-    "version": "2.7.0",
-    "cksum": "4286723485 21693",
+    "version": "2.8.0",
+    "cksum": "293994447 22064",
     "tables": {
         "SB_Global": {
             "columns": {
@@ -43,6 +43,15 @@
                                               "max": "unlimited"}}},
             "isRoot": true,
             "indexes": [["name"]]},
+        "Chassis_Private": {
+            "columns": {
+                "name": {"type": "string"},
+                "alive_at": {"type": "string"},
+                "external_ids": {
+                    "type": {"key": "string", "value": "string",
+                             "min": 0, "max": "unlimited"}}},
+            "isRoot": true,
+            "indexes": [["name"]]},
         "Encap": {
             "columns": {
                 "type": {"type": {"key": {
diff --git a/ovn-sb.xml b/ovn-sb.xml
index 3ae9d4f92..8c9822fdb 100644
--- a/ovn-sb.xml
+++ b/ovn-sb.xml
@@ -366,6 +366,41 @@
     </group>
   </table>
 
+  <table name="Chassis_Private" title="Chassis Private">
+    <p>
+      Each row in this table maintains per chassis private data that are
+      accessed only by the owning chassis (write only) and ovn-northd, not by
+      any other chassis.  These data are stored in this separate table instead
+      of the <ref table="Chassis"/> table for performance considerations:
+      the rows in this table can be conditionally monitored by chassises so
+      that each chassis only get update notifications for its own row, to avoid
+      unnecessary chassis private data update flooding in a large scale
+      deployment.  (Future: this separation can be avoided if ovsdb conditional
+      monitoring is supported on a set of columns)
+    </p>
+
+    <column name="name">
+      The name of the chassis that owns these chassis-private data.
+    </column>
+
+    <column name="alive_at">
+      A timestamp indicating the last time ovn-controller
+      signalized it's alive. For monitoring purposes, setting the
+      chassis_liveness_interval configuration to the OVN_Northhbound's
+      <ref table="NB_Global" column="options"/> with an integer value (in
+      seconds) causes the <code>ovn-controller</code> to update this
+      column with a timestamp every N seconds. If the value is not set
+      or 0, then <code>ovn-controller</code> doesn't update this column.
+    </column>
+
+    <group title="Common Columns">
+      The overall purpose of these columns is described under <code>Common
+      Columns</code> at the beginning of this document.
+
+      <column name="external_ids"/>
+    </group>
+  </table>
+
   <table name="Encap" title="Encapsulation Types">
     <p>
       The <ref column="encaps" table="Chassis"/> column in the <ref
-- 
2.25.0

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