slack-19.0: support consul topo stale reads

go/flags/endtoend/vtbackup.txt

@@ -221,6 +221,7 @@ Flags:
       --tablet_manager_grpc_key string                              the key to use to connect
       --tablet_manager_grpc_server_name string                      the server name to use to validate server certificate
       --tablet_manager_protocol string                              Protocol to use to make tabletmanager RPCs to vttablets. (default "grpc")
+      --topo_consul_allow_stale_reads                               Allow stale reads from consul servers
       --topo_consul_idle_conn_timeout duration                      Maximum amount of time to pool idle connections. (default 1m30s)
       --topo_consul_lock_delay duration                             LockDelay for consul session. (default 15s)
       --topo_consul_lock_session_checks string                      List of checks for consul session. (default "serfHealth")

go/flags/endtoend/vtcombo.txt

@@ -365,6 +365,7 @@ Flags:
       --tablet_refresh_known_tablets                                     Whether to reload the tablet's address/port map from topo in case they change. (default true)
       --tablet_url_template string                                       Format string describing debug tablet url formatting. See getTabletDebugURL() for how to customize this. (default "http://{{ "{{.GetTabletHostPort}}" }}")
       --throttle_tablet_types string                                     Comma separated VTTablet types to be considered by the throttler. default: 'replica'. example: 'replica,rdonly'. 'replica' always implicitly included (default "replica")
+      --topo_consul_allow_stale_reads                                    Allow stale reads from consul servers
       --topo_consul_idle_conn_timeout duration                           Maximum amount of time to pool idle connections. (default 1m30s)
       --topo_consul_lock_delay duration                                  LockDelay for consul session. (default 15s)
       --topo_consul_lock_session_checks string                           List of checks for consul session. (default "serfHealth")

go/flags/endtoend/vtctld.txt

@@ -155,6 +155,7 @@ Flags:
       --tablet_refresh_interval duration                                 Tablet refresh interval. (default 1m0s)
       --tablet_refresh_known_tablets                                     Whether to reload the tablet's address/port map from topo in case they change. (default true)
       --tablet_url_template string                                       Format string describing debug tablet url formatting. See getTabletDebugURL() for how to customize this. (default "http://{{ "{{.GetTabletHostPort}}" }}")
+      --topo_consul_allow_stale_reads                                    Allow stale reads from consul servers
       --topo_consul_idle_conn_timeout duration                           Maximum amount of time to pool idle connections. (default 1m30s)
       --topo_consul_lock_delay duration                                  LockDelay for consul session. (default 15s)
       --topo_consul_lock_session_checks string                           List of checks for consul session. (default "serfHealth")

go/flags/endtoend/vtgate.txt

@@ -213,6 +213,7 @@ Flags:
       --tablet_refresh_known_tablets                                     Whether to reload the tablet's address/port map from topo in case they change. (default true)
       --tablet_types_to_wait strings                                     Wait till connected for specified tablet types during Gateway initialization. Should be provided as a comma-separated set of tablet types.
       --tablet_url_template string                                       Format string describing debug tablet url formatting. See getTabletDebugURL() for how to customize this. (default "http://{{ "{{.GetTabletHostPort}}" }}")
+      --topo_consul_allow_stale_reads                                    Allow stale reads from consul servers
       --topo_consul_idle_conn_timeout duration                           Maximum amount of time to pool idle connections. (default 1m30s)
       --topo_consul_lock_delay duration                                  LockDelay for consul session. (default 15s)
       --topo_consul_lock_session_checks string                           List of checks for consul session. (default "serfHealth")

go/flags/endtoend/vtorc.txt

@@ -93,6 +93,7 @@ Flags:
       --tablet_manager_protocol string                              Protocol to use to make tabletmanager RPCs to vttablets. (default "grpc")
       --tolerable-replication-lag duration                          Amount of replication lag that is considered acceptable for a tablet to be eligible for promotion when Vitess makes the choice of a new primary in PRS
       --topo-information-refresh-duration duration                  Timer duration on which VTOrc refreshes the keyspace and vttablet records from the topology server (default 15s)
+      --topo_consul_allow_stale_reads                               Allow stale reads from consul servers
       --topo_consul_idle_conn_timeout duration                      Maximum amount of time to pool idle connections. (default 1m30s)
       --topo_consul_lock_delay duration                             LockDelay for consul session. (default 15s)
       --topo_consul_lock_session_checks string                      List of checks for consul session. (default "serfHealth")

go/flags/endtoend/vttablet.txt

@@ -367,6 +367,7 @@ Flags:
       --tablet_manager_protocol string                                   Protocol to use to make tabletmanager RPCs to vttablets. (default "grpc")
       --tablet_protocol string                                           Protocol to use to make queryservice RPCs to vttablets. (default "grpc")
       --throttle_tablet_types string                                     Comma separated VTTablet types to be considered by the throttler. default: 'replica'. example: 'replica,rdonly'. 'replica' always implicitly included (default "replica")
+      --topo_consul_allow_stale_reads                                    Allow stale reads from consul servers
       --topo_consul_idle_conn_timeout duration                           Maximum amount of time to pool idle connections. (default 1m30s)
       --topo_consul_lock_delay duration                                  LockDelay for consul session. (default 15s)
       --topo_consul_lock_session_checks string                           List of checks for consul session. (default "serfHealth")

go/flags/endtoend/vttestserver.txt

@@ -137,6 +137,7 @@ Flags:
       --tablet_manager_grpc_server_name string                           the server name to use to validate server certificate
       --tablet_manager_protocol string                                   Protocol to use to make tabletmanager RPCs to vttablets. (default "grpc")
       --tablet_refresh_interval duration                                 Interval at which vtgate refreshes tablet information from topology server. (default 10s)
+      --topo_consul_allow_stale_reads                                    Allow stale reads from consul servers
       --topo_consul_idle_conn_timeout duration                           Maximum amount of time to pool idle connections. (default 1m30s)
       --topo_consul_lock_delay duration                                  LockDelay for consul session. (default 15s)
       --topo_consul_lock_session_checks string                           List of checks for consul session. (default "serfHealth")

go/vt/topo/consultopo/file.go

@@ -87,7 +87,9 @@ func (s *Server) Update(ctx context.Context, filePath string, contents []byte, v
 func (s *Server) Get(ctx context.Context, filePath string) ([]byte, topo.Version, error) {
 	nodePath := path.Join(s.root, filePath)
 
-	pair, _, err := s.kv.Get(nodePath, nil)
+	pair, _, err := s.kv.Get(nodePath, &api.QueryOptions{
+		AllowStale: consulAllowStaleReads,
+	})
 	if err != nil {
 		return nil, nil, err
 	}
@@ -102,7 +104,9 @@ func (s *Server) Get(ctx context.Context, filePath string) ([]byte, topo.Version
 func (s *Server) List(ctx context.Context, filePathPrefix string) ([]topo.KVInfo, error) {
 	nodePathPrefix := path.Join(s.root, filePathPrefix)
 
-	pairs, _, err := s.kv.List(nodePathPrefix, nil)
+	pairs, _, err := s.kv.List(nodePathPrefix, &api.QueryOptions{
+		AllowStale: consulAllowStaleReads,
+	})
 	if err != nil {
 		return []topo.KVInfo{}, err
 	}

go/vt/topo/consultopo/server.go

@@ -45,6 +45,7 @@ var (
 	consulMaxConnsPerHost   int = 250 // do not use client default of 0/unlimited
 	consulMaxIdleConns      int
 	consulIdleConnTimeout   time.Duration
+	consulAllowStaleReads   bool
 )
 
 func init() {
@@ -64,6 +65,7 @@ func registerServerFlags(fs *pflag.FlagSet) {
 	fs.IntVar(&consulMaxConnsPerHost, "topo_consul_max_conns_per_host", consulMaxConnsPerHost, "Maximum number of consul connections per host.")
 	fs.IntVar(&consulMaxIdleConns, "topo_consul_max_idle_conns", defaultConsulPooledTransport.MaxIdleConns, "Maximum number of idle consul connections.")
 	fs.DurationVar(&consulIdleConnTimeout, "topo_consul_idle_conn_timeout", defaultConsulPooledTransport.IdleConnTimeout, "Maximum amount of time to pool idle connections.")
+	fs.BoolVar(&consulAllowStaleReads, "topo_consul_allow_stale_reads", consulAllowStaleReads, "Allow stale reads from consul servers")
 }
 
 // ClientAuthCred credential to use for consul clusters