RUBY-1805 remove strict check that a server has a known description when looking at features (#1470)

Author: p-mongo

lib/mongo/client.rb

@@ -32,6 +32,17 @@ class Client
       :write, :write_concern,
       :retry_reads, :max_read_retries, :read_retry_interval,
       :retry_writes, :max_write_retries,
+
+      # Options which cannot currently be here:
+      #
+      # :server_selection_timeout
+      # Server selection timeout is used by cluster constructor to figure out
+      # how long to wait for initial scan in compatibility mode, but once
+      # the cluster is initialized it no longer uses this timeout.
+      # Unfortunately server selector reads server selection timeout out of
+      # the cluster, and this behavior is required by Cluster#next_primary
+      # which takes no arguments. When next_primary is removed we can revsit
+      # using the same cluster object with different server selection timeouts.
     ].freeze
 
     # Valid client options.

lib/mongo/server/description.rb

@@ -217,7 +217,7 @@ def initialize(address, config = {}, average_round_trip_time = nil)
       # @return [ Features ] features The features for the server.
       def features
         if unknown?
-          raise ArgumentError, "An unknown server's features are not known"
+          return Features.new(0..0, address.to_s)
         end
         @features
       end

spec/integration/client_spec.rb

@@ -0,0 +1,44 @@
+require 'spec_helper'
+
+describe 'Client' do
+  context 'after client is disconnected' do
+    let(:client) { authorized_client.with(server_selection_timeout: 1) }
+
+    before do
+      client.close
+    end
+
+    it 'is still usable for operations' do
+      resp = client.database.command(ismaster: 1)
+      expect(resp).to be_a(Mongo::Operation::Result)
+    end
+
+    it 'is still usable for operations that can use sessions' do
+      client['collection'].insert_one(test: 1)
+    end
+
+    context 'after all servers are marked unknown' do
+      before do
+        client.cluster.servers.each do |server|
+          server.unknown!
+        end
+      end
+
+      context 'operation that never uses sessions' do
+        it 'fails server selection' do
+          expect do
+            client.database.command(ismaster: 1)
+          end.to raise_error(Mongo::Error::NoServerAvailable)
+        end
+      end
+
+      context 'operation that can use sessions' do
+        it 'fails server selection' do
+          expect do
+            client['collection'].insert_one(test: 1)
+          end.to raise_error(Mongo::Error::NoServerAvailable)
+        end
+      end
+    end
+  end
+end

spec/integration/server_spec.rb

@@ -0,0 +1,48 @@
+require 'spec_helper'
+
+describe 'Server' do
+  let(:client) { authorized_client }
+
+  let(:server) { client.cluster.next_primary }
+
+  let(:collection) { client['collection'] }
+  let(:view) { Mongo::Collection::View.new(collection) }
+
+  describe 'operations when client/cluster are disconnected' do
+    # Server versions lower than 3.4 use the legacy find result
+    min_server_fcv '3.4'
+
+    context 'normal server' do
+      it 'can be used for reads' do
+        result = view.send(:send_initial_query, server)
+        expect(result).to be_a(Mongo::Operation::Find::Result)
+      end
+    end
+
+    context 'known server in disconnected cluster' do
+      before do
+        client.close
+        expect(server).not_to be_unknown
+      end
+
+      it 'can be used for reads' do
+        result = view.send(:send_initial_query, server)
+        expect(result).to be_a(Mongo::Operation::Find::Result)
+      end
+    end
+
+    context 'unknown server in disconnected cluster' do
+      before do
+        client.close
+        server.unknown!
+        expect(server).to be_unknown
+      end
+
+      it 'can be used for reads' do
+        result = view.send(:send_initial_query, server)
+        # Driver falls back to the oldest MongoDB protocol
+        expect(result).to be_a(Mongo::Operation::Find::Legacy::Result)
+      end
+    end
+  end
+end