Add native support for active-standby HA in ovn-northd by having each
instance attempt to acquire an OVSDB lock. Only the instance of
ovn-northd that currently holds the lock will make active changes to
the OVN databases.
Signed-off-by: Russell Bryant <russ...@ovn.org>
---
NEWS | 1 +
ovn/northd/ovn-northd.8.xml | 9 +++++++++
ovn/northd/ovn-northd.c | 40 +++++++++++++++++++++++++++++++---------
3 files changed, 41 insertions(+), 9 deletions(-)
diff --git a/NEWS b/NEWS
index facea0228..f3cdd2443 100644
--- a/NEWS
+++ b/NEWS
@@ -49,6 +49,7 @@ Post-v2.7.0
one chassis is specified, OVN will manage high availability for that
gateway.
* Add support for ACL logging.
+ * ovn-northd now has native support for active-standby high availability.
- Tracing with ofproto/trace now traces through recirculation.
- OVSDB:
* New support for role-based access control (see ovsdb-server(1)).
diff --git a/ovn/northd/ovn-northd.8.xml b/ovn/northd/ovn-northd.8.xml
index 1527e8a60..0d85ec0d2 100644
--- a/ovn/northd/ovn-northd.8.xml
+++ b/ovn/northd/ovn-northd.8.xml
@@ -72,6 +72,15 @@
</dl>
</p>
+ <h1>Active-Standby for High Availability</h1>
+ <p>
+ You may run <code>ovn-northd</code> more than once in an OVN deployment.
+ OVN will automatically ensure that only one of them is active at a time.
+ If multiple instances of <code>ovn-northd</code> are running and the
+ active <code>ovn-northd</code> fails, one of the hot standby instances
+ of <code>ovn-northd</code> will automatically take over.
+ </p>
+
<h1>Logical Flow Table Structure</h1>
<p>
diff --git a/ovn/northd/ovn-northd.c b/ovn/northd/ovn-northd.c
index 10e0c7ce0..3d2be4267 100644
--- a/ovn/northd/ovn-northd.c
+++ b/ovn/northd/ovn-northd.c
@@ -6531,6 +6531,12 @@ main(int argc, char *argv[])
ovsdb_idl_add_column(ovnsb_idl_loop.idl, &sbrec_chassis_col_nb_cfg);
ovsdb_idl_add_column(ovnsb_idl_loop.idl, &sbrec_chassis_col_name);
+ /* Ensure that only a single ovn-northd is active in the deployment by
+ * acquiring a lock called "ovn_northd" on the southbound database
+ * and then only performing DB transactions if the lock is held. */
+ ovsdb_idl_set_lock(ovnsb_idl_loop.idl, "ovn_northd");
+ bool had_lock = false;
+
/* Main loop. */
exiting = false;
while (!exiting) {
@@ -6541,15 +6547,29 @@ main(int argc, char *argv[])
.ovnsb_txn = ovsdb_idl_loop_run(&ovnsb_idl_loop),
};
- struct chassis_index chassis_index;
- chassis_index_init(&chassis_index, ctx.ovnsb_idl);
+ 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;
+ }
- ovnnb_db_run(&ctx, &chassis_index, &ovnsb_idl_loop);
- ovnsb_db_run(&ctx, &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);
+ struct chassis_index chassis_index;
+ bool destroy_chassis_index = false;
+ if (ovsdb_idl_has_lock(ovnsb_idl_loop.idl)) {
+ chassis_index_init(&chassis_index, ctx.ovnsb_idl);
+ destroy_chassis_index = true;
+
+ ovnnb_db_run(&ctx, &chassis_index, &ovnsb_idl_loop);
+ ovnsb_db_run(&ctx, &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);
+ }
}
unixctl_server_run(unixctl);
@@ -6565,7 +6585,9 @@ main(int argc, char *argv[])
exiting = true;
}
- chassis_index_destroy(&chassis_index);
+ if (destroy_chassis_index) {
+ chassis_index_destroy(&chassis_index);
+ }
}
unixctl_server_destroy(unixctl);
--
2.13.3
_______________________________________________
dev mailing list
d...@openvswitch.org
https://mail.openvswitch.org/mailman/listinfo/ovs-dev
