[ovs-dev] [branch2.12] ovn-northd: Add the option to pause and resume

nusiddiq at redhat.com nusiddiq at redhat.com
Thu Aug 1 06:31:56 UTC 2019


From: Numan Siddique <nusiddiq at redhat.com>

This patch adds 3 unixctl socket comments - pause, resume and is-paused.

Usage: ovs-appctl -t ovn-northd pause/resume/is-paused

This feature will be useful if the CMS wants to
  - deploy OVN DB servers in active/passive mode and
  - run ovn-northd on all these nodes and use unix ctl sockets to
    connect to the local OVN DB servers.

On the nodes where OVN Db ovsdb-servers are in passive mode, the local ovn-northds
will process the DB changes and compute logical flows to be thrown out later,
because write transactions are not allowed by these ovsdb-servers. It results in
unncessary CPU usage.

With these commands, CMS can pause ovn-northd on these node. A node
which becomes master, can resume the ovn-northd.

One use case is to use this feature in ovn-kubernetes with the above deployment model.

Acked-by: Mark Michelson <mmichels at redhat.com>
Acked-by: Dumitru Ceara <dceara at redhat.com>
Signed-off-by: Numan Siddique <nusiddiq at redhat.com>
(cherry picked from ovn commit 03894e3e2374069c06ae97dafb24fb4fcb8c8e61)
---
 ovn/northd/ovn-northd.8.xml |  48 ++++++++++++++++
 ovn/northd/ovn-northd.c     | 111 +++++++++++++++++++++++++++---------
 tests/ovn-northd.at         |  38 ++++++++++++
 3 files changed, 169 insertions(+), 28 deletions(-)

diff --git a/ovn/northd/ovn-northd.8.xml b/ovn/northd/ovn-northd.8.xml
index d2267de0e..1d0243656 100644
--- a/ovn/northd/ovn-northd.8.xml
+++ b/ovn/northd/ovn-northd.8.xml
@@ -70,6 +70,23 @@
       <dd>
         Causes <code>ovn-northd</code> to gracefully terminate.
       </dd>
+
+      <dt><code>pause</code></dt>
+      <dd>
+        Pauses the ovn-northd operation from processing any Northbound and
+        Southbound database changes.
+      </dd>
+
+      <dt><code>resume</code></dt>
+      <dd>
+        Resumes the ovn-northd operation to process Northbound and
+        Southbound database contents and generate logical flows.
+      </dd>
+
+      <dt><code>is-paused</code></dt>
+      <dd>
+        Returns "true" if ovn-northd is currently paused, "false" otherwise.
+      </dd>
       </dl>
     </p>
 
@@ -82,6 +99,37 @@
       of <code>ovn-northd</code> will automatically take over.
     </p>
 
+    <h2> Active-Standby with multiple OVN DB servers</h2>
+    <p>
+      You may run multiple OVN DB servers in an OVN deployment with:
+      <ul>
+        <li>
+          OVN DB servers deployed in active/passive mode with one active
+          and multiple passive ovsdb-servers.
+        </li>
+
+        <li>
+          <code>ovn-northd</code> also deployed on all these nodes,
+          using unix ctl sockets to connect to the local OVN DB servers.
+        </li>
+      </ul>
+    </p>
+
+    <p>
+      In such deployments, the ovn-northds on the passive nodes will process
+      the DB changes and compute logical flows to be thrown out later,
+      because write transactions are not allowed by the passive ovsdb-servers.
+      It results in unnecessary CPU usage.
+    </p>
+
+    <p>
+      With the help of runtime management command <code>pause</code>, you can
+      pause <code>ovn-northd</code> on these nodes. When a passive node
+      becomes master, you can use the runtime management command
+      <code>resume</code> to resume the <code>ovn-northd</code> to process the
+      DB changes.
+    </p>
+
     <h1>Logical Flow Table Structure</h1>
 
     <p>
diff --git a/ovn/northd/ovn-northd.c b/ovn/northd/ovn-northd.c
index eb6c47cad..2e96e9cf4 100644
--- a/ovn/northd/ovn-northd.c
+++ b/ovn/northd/ovn-northd.c
@@ -52,6 +52,9 @@
 VLOG_DEFINE_THIS_MODULE(ovn_northd);
 
 static unixctl_cb_func ovn_northd_exit;
+static unixctl_cb_func ovn_northd_pause;
+static unixctl_cb_func ovn_northd_resume;
+static unixctl_cb_func ovn_northd_is_paused;
 
 struct northd_context {
     struct ovsdb_idl *ovnnb_idl;
@@ -9182,6 +9185,7 @@ main(int argc, char *argv[])
     struct unixctl_server *unixctl;
     int retval;
     bool exiting;
+    bool paused;
 
     fatal_ignore_sigpipe();
     ovs_cmdl_proctitle_init(argc, argv);
@@ -9196,6 +9200,10 @@ main(int argc, char *argv[])
         exit(EXIT_FAILURE);
     }
     unixctl_command_register("exit", "", 0, 0, ovn_northd_exit, &exiting);
+    unixctl_command_register("pause", "", 0, 0, ovn_northd_pause, &paused);
+    unixctl_command_register("resume", "", 0, 0, ovn_northd_resume, &paused);
+    unixctl_command_register("is-paused", "", 0, 0, ovn_northd_is_paused,
+                             &paused);
 
     daemonize_complete();
 
@@ -9384,34 +9392,51 @@ main(int argc, char *argv[])
 
     /* Main loop. */
     exiting = false;
+    paused = false;
     while (!exiting) {
-        struct northd_context ctx = {
-            .ovnnb_idl = ovnnb_idl_loop.idl,
-            .ovnnb_txn = ovsdb_idl_loop_run(&ovnnb_idl_loop),
-            .ovnsb_idl = ovnsb_idl_loop.idl,
-            .ovnsb_txn = ovsdb_idl_loop_run(&ovnsb_idl_loop),
-            .sbrec_ha_chassis_grp_by_name = sbrec_ha_chassis_grp_by_name,
-            .sbrec_mcast_group_by_name_dp = sbrec_mcast_group_by_name_dp,
-            .sbrec_ip_mcast_by_dp = sbrec_ip_mcast_by_dp,
-        };
-
-        if (!had_lock && ovsdb_idl_has_lock(ovnsb_idl_loop.idl)) {
-            VLOG_INFO("ovn-northd lock acquired. "
-                      "This ovn-northd instance is now active.");
-            had_lock = true;
-        } else if (had_lock && !ovsdb_idl_has_lock(ovnsb_idl_loop.idl)) {
-            VLOG_INFO("ovn-northd lock lost. "
-                      "This ovn-northd instance is now on standby.");
-            had_lock = false;
-        }
-
-        if (ovsdb_idl_has_lock(ovnsb_idl_loop.idl)) {
-            ovn_db_run(&ctx, sbrec_chassis_by_name, &ovnsb_idl_loop);
-            if (ctx.ovnsb_txn) {
-                check_and_add_supported_dhcp_opts_to_sb_db(&ctx);
-                check_and_add_supported_dhcpv6_opts_to_sb_db(&ctx);
-                check_and_update_rbac(&ctx);
+        if (!paused) {
+            struct northd_context ctx = {
+                .ovnnb_idl = ovnnb_idl_loop.idl,
+                .ovnnb_txn = ovsdb_idl_loop_run(&ovnnb_idl_loop),
+                .ovnsb_idl = ovnsb_idl_loop.idl,
+                .ovnsb_txn = ovsdb_idl_loop_run(&ovnsb_idl_loop),
+                .sbrec_ha_chassis_grp_by_name = sbrec_ha_chassis_grp_by_name,
+                .sbrec_mcast_group_by_name_dp = sbrec_mcast_group_by_name_dp,
+                .sbrec_ip_mcast_by_dp = sbrec_ip_mcast_by_dp,
+            };
+
+            if (!had_lock && ovsdb_idl_has_lock(ovnsb_idl_loop.idl)) {
+                VLOG_INFO("ovn-northd lock acquired. "
+                        "This ovn-northd instance is now active.");
+                had_lock = true;
+            } else if (had_lock && !ovsdb_idl_has_lock(ovnsb_idl_loop.idl)) {
+                VLOG_INFO("ovn-northd lock lost. "
+                        "This ovn-northd instance is now on standby.");
+                had_lock = false;
             }
+
+            if (ovsdb_idl_has_lock(ovnsb_idl_loop.idl)) {
+                ovn_db_run(&ctx, sbrec_chassis_by_name, &ovnsb_idl_loop);
+                if (ctx.ovnsb_txn) {
+                    check_and_add_supported_dhcp_opts_to_sb_db(&ctx);
+                    check_and_add_supported_dhcpv6_opts_to_sb_db(&ctx);
+                    check_and_update_rbac(&ctx);
+                }
+            }
+
+            ovsdb_idl_loop_commit_and_wait(&ovnnb_idl_loop);
+            ovsdb_idl_loop_commit_and_wait(&ovnsb_idl_loop);
+        } else {
+            /* ovn-northd is paused
+             *    - we still want to handle any db updates and update the
+             *      local IDL. Otherwise, when it is resumed, the local IDL
+             *      copy will be out of sync.
+             *    - but we don't want to create any txns.
+             * */
+            ovsdb_idl_run(ovnnb_idl_loop.idl);
+            ovsdb_idl_run(ovnsb_idl_loop.idl);
+            ovsdb_idl_wait(ovnnb_idl_loop.idl);
+            ovsdb_idl_wait(ovnsb_idl_loop.idl);
         }
 
         unixctl_server_run(unixctl);
@@ -9419,8 +9444,6 @@ main(int argc, char *argv[])
         if (exiting) {
             poll_immediate_wake();
         }
-        ovsdb_idl_loop_commit_and_wait(&ovnnb_idl_loop);
-        ovsdb_idl_loop_commit_and_wait(&ovnsb_idl_loop);
 
         poll_block();
         if (should_service_stop()) {
@@ -9445,3 +9468,35 @@ ovn_northd_exit(struct unixctl_conn *conn, int argc OVS_UNUSED,
 
     unixctl_command_reply(conn, NULL);
 }
+
+static void
+ovn_northd_pause(struct unixctl_conn *conn, int argc OVS_UNUSED,
+                const char *argv[] OVS_UNUSED, void *pause_)
+{
+    bool *pause = pause_;
+    *pause = true;
+
+    unixctl_command_reply(conn, NULL);
+}
+
+static void
+ovn_northd_resume(struct unixctl_conn *conn, int argc OVS_UNUSED,
+                  const char *argv[] OVS_UNUSED, void *pause_)
+{
+    bool *pause = pause_;
+    *pause = false;
+
+    unixctl_command_reply(conn, NULL);
+}
+
+static void
+ovn_northd_is_paused(struct unixctl_conn *conn, int argc OVS_UNUSED,
+                     const char *argv[] OVS_UNUSED, void *paused_)
+{
+    bool *paused = paused_;
+    if (*paused) {
+        unixctl_command_reply(conn, "true");
+    } else {
+        unixctl_command_reply(conn, "false");
+    }
+}
diff --git a/tests/ovn-northd.at b/tests/ovn-northd.at
index 62e58fd0e..0dea04edc 100644
--- a/tests/ovn-northd.at
+++ b/tests/ovn-northd.at
@@ -898,3 +898,41 @@ as northd
 OVS_APP_EXIT_AND_WAIT([ovn-northd])
 
 AT_CLEANUP
+
+AT_SETUP([ovn -- ovn-northd pause and resume])
+AT_SKIP_IF([test $HAVE_PYTHON = no])
+ovn_start
+
+AT_CHECK([test xfalse = x`as northd ovs-appctl -t ovn-northd is-paused`])
+
+ovn-nbctl ls-add sw0
+
+OVS_WAIT_UNTIL([
+    ovn-sbctl lflow-list sw0
+    test 0 = $?])
+
+ovn-nbctl ls-del sw0
+OVS_WAIT_UNTIL([
+    ovn-sbctl lflow-list sw0
+    test 1 = $?])
+
+# Now pause the ovn-northd
+as northd ovs-appctl -t ovn-northd pause
+AT_CHECK([test xtrue = x`as northd ovs-appctl -t ovn-northd is-paused`])
+
+ovn-nbctl ls-add sw0
+
+# There should be no logical flows for sw0 datapath.
+OVS_WAIT_UNTIL([
+    ovn-sbctl lflow-list sw0
+    test 1 = $?])
+
+# Now resume ovn-northd
+as northd ovs-appctl -t ovn-northd resume
+AT_CHECK([test xfalse = x`as northd ovs-appctl -t ovn-northd is-paused`])
+
+OVS_WAIT_UNTIL([
+    ovn-sbctl lflow-list sw0
+    test 0 = $?])
+
+AT_CLEANUP
-- 
2.21.0



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