cluster.rb in mongo-2.11.2

- old
+ new

@@ -160,17 +160,14 @@
         # SDAM responses.
         @connecting = @connected = false
         return
       end
 
-      # Need to record start time prior to starting monitoring
-      start_time = Time.now
+      # Update instance variables prior to starting monitoring threads.
+      @connecting = false
+      @connected = true
 
-      servers.each do |server|
-        server.start_monitoring
-      end
-
       if options[:cleanup] != false
         @cursor_reaper = CursorReaper.new
         @socket_reaper = SocketReaper.new(self)
         @periodic_executor = PeriodicExecutor.new([
           @cursor_reaper, @socket_reaper,
@@ -180,13 +177,17 @@
           {}, @periodic_executor, @session_pool))
 
         @periodic_executor.run!
       end
 
-      @connecting = false
-      @connected = true
+      # Need to record start time prior to starting monitoring
+      start_time = Time.now
 
+      servers.each do |server|
+        server.start_monitoring
+      end
+
       if options[:scan] != false
         server_selection_timeout = options[:server_selection_timeout] || ServerSelector::SERVER_SELECTION_TIMEOUT
         # The server selection timeout can be very short especially in
         # tests, when the client waits for a synchronous scan before
         # starting server selection. Limiting the scan to server selection time
@@ -741,34 +742,53 @@
     #
     # @example Remove the server from the cluster.
     #   server.remove('127.0.0.1:27017')
     #
     # @param [ String ] host The host/port or socket address.
+    # @param [ true | false ] disconnect Whether to disconnect the servers
+    #   being removed. For internal driver use only.
     #
-    # @return [ true|false ] Whether any servers were removed.
+    # @return [ Array<Server> | true | false ] If disconnect is any value other
+    #   than false, including nil, returns whether any servers were removed.
+    #   If disconnect is false, returns an array of servers that were removed
+    #   (and should be disconnected by the caller).
     #
-    # @since 2.0.0, return value added in 2.7.0
-    def remove(host)
+    # @note The return value of this method is not part of the driver's
+    #   public API.
+    #
+    # @since 2.0.0
+    def remove(host, disconnect: true)
       address = Address.new(host)
       removed_servers = @servers.select { |s| s.address == address }
       @update_lock.synchronize { @servers = @servers - removed_servers }
-      removed_servers.each do |server|
-        if server.connected?
-          server.disconnect!
-          publish_sdam_event(
-            Monitoring::SERVER_CLOSED,
-            Monitoring::Event::ServerClosed.new(address, topology)
-          )
+      if disconnect != false
+        removed_servers.each do |server|
+          disconnect_server_if_connected(server)
         end
       end
-      removed_servers.any?
+      if disconnect != false
+        removed_servers.any?
+      else
+        removed_servers
+      end
     end
 
     # @api private
     def update_topology(new_topology)
       old_topology = topology
       @topology = new_topology
+
+      # If new topology has data bearing servers, we know for sure whether
+      # sessions are supported - update our cached value.
+      # If new topology has no data bearing servers, leave the old value
+      # as it is and sessions_supported? method will perform server selection
+      # to try to determine session support accurately, falling back to the
+      # last known value.
+      if topology.data_bearing_servers?
+        @sessions_supported = !!topology.logical_session_timeout
+      end
+
       publish_sdam_event(
         Monitoring::TOPOLOGY_CHANGED,
         Monitoring::Event::TopologyChanged.new(old_topology, topology)
       )
     end
@@ -776,55 +796,51 @@
     # @api private
     def servers_list
       @update_lock.synchronize { @servers.dup }
     end
 
-    private
-
-    # If options[:session] is set, validates that session and returns it.
-    # If deployment supports sessions, creates a new session and returns it.
-    # The session is implicit unless options[:implicit] is given.
-    # If deployment does not support session, returns nil.
-    #
-    # @note This method will return nil if deployment has no data-bearing
-    #   servers at the time of the call.
-    def get_session(client, options = {})
-      return options[:session].validate!(self) if options[:session]
-      if sessions_supported?
-        Session.new(@session_pool.checkout, client, { implicit: true }.merge(options))
+    # @api private
+    def disconnect_server_if_connected(server)
+      if server.connected?
+        server.disconnect!
+        publish_sdam_event(
+          Monitoring::SERVER_CLOSED,
+          Monitoring::Event::ServerClosed.new(server.address, topology)
+        )
       end
     end
 
-    def with_session(client, options = {})
-      session = get_session(client, options)
-      yield(session)
-    ensure
-      session.end_session if (session && session.implicit?)
-    end
-
-    # Returns whether the deployment (as this term is defined in the sessions
-    # spec) supports sessions.
+    # Returns whether the deployment that the driver is connected to supports
+    # sessions.
     #
-    # @note If the cluster has no data bearing servers, for example because
-    #   the deployment is in the middle of a failover, this method returns
-    #   false.
+    # Session support may change over time, for example due to servers in the
+    # deployment being upgraded or downgraded. This method returns the
+    # current information if the client is connected to at least one data
+    # bearing server. If the client is currently not connected to any data
+    # bearing servers, this method returns the last known value for whether
+    # the deployment supports sessions.
     #
-    # @note This method returns as soon as the driver connects to any single
-    #   server in the deployment. Whether deployment overall supports sessions
-    #   can change depending on how many servers have been contacted, if
-    #   the servers are configured differently.
+    # @return [ true | false ] Whether deployment supports sessions.
+    # @api private
     def sessions_supported?
       if topology.data_bearing_servers?
         return !!topology.logical_session_timeout
       end
 
+      # No data bearing servers known - perform server selection to try to
+      # get a response from at least one of them, to return an accurate
+      # assessment of whether sessions are currently supported.
       begin
         ServerSelector.get(mode: :primary_preferred).select_server(self)
         !!topology.logical_session_timeout
       rescue Error::NoServerAvailable
-        false
+        # We haven't been able to contact any servers - use last known
+        # value for esssion support.
+        @sessions_supported || false
       end
     end
+
+    private
 
     # @api private
     def start_stop_srv_monitor
       # SRV URI is either always given or not for a given cluster, if one
       # wasn't given we shouldn't ever have an SRV monitor to manage.