selectable.rb in mongo-2.7.0.rc0

- old
+ new

@@ -1,6 +1,6 @@
-# Copyright (C) 2014-2018 MongoDB, Inc.
+# Copyright (C) 2014-2019 MongoDB, Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
@@ -58,10 +58,14 @@
       #
       # @param [ Hash ] options The server preference options.
       #
       # @option options [ Integer ] :local_threshold The local threshold boundary for
       #  nearest selection in seconds.
+      # @option options [ Integer ] max_staleness The maximum replication lag,
+      #   in seconds, that a secondary can suffer and still be eligible for a read.
+      #   A value of -1 is treated identically to nil, which is to not
+      #   have a maximum staleness.
       #
       # @raise [ Error::InvalidServerPreference ] If tag sets are specified
       #   but not allowed.
       #
       # @since 2.0.0
@@ -98,23 +102,41 @@
         @local_threshold = cluster.options[:local_threshold] || LOCAL_THRESHOLD
         @server_selection_timeout = cluster.options[:server_selection_timeout] || SERVER_SELECTION_TIMEOUT
         deadline = Time.now + server_selection_timeout
         while (deadline - Time.now) > 0
           servers = candidates(cluster)
+          if Lint.enabled?
+            servers.each do |server|
+              if server.average_round_trip_time.nil?
+                raise Error::LintError, "Server #{server.address} has nil average rtt"
+              end
+            end
+          end
           if servers && !servers.compact.empty?
+            unless cluster.topology.compatible?
+              raise Error::UnsupportedFeatures, cluster.topology.compatibility_error.to_s
+            end
+
+            # This list of servers may be ordered in a specific way
+            # by the selector (e.g. for secondary preferred, the first
+            # server may be a secondary and the second server may be primary)
+            # and we should take the first server here respecting the order
             server = servers.first
-            # HACK: all servers in a topology must satisfy wire protocol
-            # constraints. There is probably a better implementation than
-            # checking all servers here
-            cluster.servers.each do |a_server|
-              a_server.check_driver_support!
+
+            if cluster.topology.single? &&
+              cluster.topology.replica_set_name &&
+              cluster.topology.replica_set_name != server.description.replica_set_name
+            then
+              msg = "Cluster topology specifies replica set name #{cluster.topology.replica_set_name}, but the server has replica set name #{server.description.replica_set_name || '<nil>'}"
+              raise Error::NoServerAvailable.new(self, cluster, msg)
             end
+
             return server
           end
-          cluster.scan!
+          cluster.scan!(false)
         end
-        raise Error::NoServerAvailable.new(self)
+        raise Error::NoServerAvailable.new(self, cluster)
       end
 
       # Get the timeout for server selection.
       #
       # @example Get the server selection timeout, in seconds.
@@ -193,10 +215,14 @@
       # @since 2.0.0
       def secondaries(candidates)
         matching_servers = candidates.select(&:secondary?)
         matching_servers = filter_stale_servers(matching_servers, primary(candidates).first)
         matching_servers = match_tag_sets(matching_servers) unless tag_sets.empty?
+        # Per server selection spec the server selected MUST be a random
+        # one matching staleness and latency requirements.
+        # Selectors always pass the output of #secondaries to #nearest
+        # which shuffles the server list, fulfilling this requirement.
         matching_servers
       end
 
       # Select the near servers from a list of provided candidates, taking the
       #   local threshold into account.
@@ -231,25 +257,24 @@
         matches || []
       end
 
       def filter_stale_servers(candidates, primary = nil)
         return candidates unless @max_staleness
-        max_staleness_ms = @max_staleness * 1000
 
         if primary
           candidates.select do |server|
             validate_max_staleness_support!(server)
             staleness = (server.last_scan - server.last_write_date) -
                         (primary.last_scan - primary.last_write_date)  +
-                        (server.heartbeat_frequency_seconds * 1000)
-            staleness <= max_staleness_ms
+                        server.heartbeat_frequency_seconds
+            staleness <= @max_staleness
           end
         else
           max_write_date = candidates.collect(&:last_write_date).max
           candidates.select do |server|
             validate_max_staleness_support!(server)
-            staleness = max_write_date - server.last_write_date + (server.heartbeat_frequency_seconds * 1000)
-            staleness <= max_staleness_ms
+            staleness = max_write_date - server.last_write_date + server.heartbeat_frequency_seconds
+            staleness <= @max_staleness
           end
         end
       end
 
       def validate!