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

From: Numan Siddique <nusiddiq@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@redhat.com>
Acked-by: Dumitru Ceara <dceara@redhat.com>
Signed-off-by: Numan Siddique <nusiddiq@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(-)

Thanks.  I merged this into branch-2.12.

--Justin


> On Jul 31, 2019, at 11:31 PM, nusiddiq@redhat.com wrote:
> 
> From: Numan Siddique <nusiddiq@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@redhat.com>
> Acked-by: Dumitru Ceara <dceara@redhat.com>
> Signed-off-by: Numan Siddique <nusiddiq@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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