Fix RUBY-1935 database#command attempts to retry for EOFError (#1523)

Author: p-mongo

lib/mongo/client.rb

@@ -709,7 +709,7 @@ def list_databases(filter = {}, name_only = false, opts = {})
       cmd = { listDatabases: 1 }
       cmd[:nameOnly] = !!name_only
       cmd[:filter] = filter unless filter.empty?
-      use(Database::ADMIN).command(cmd, opts).first[Database::DATABASES]
+      use(Database::ADMIN).database.read_command(cmd, opts).first[Database::DATABASES]
     end
 
     # Returns a list of Mongo::Database objects.

lib/mongo/collection.rb

@@ -212,7 +212,7 @@ def with(new_options)
     #
     # @since 2.0.0
     def capped?
-      database.command(:collstats => name).documents[0][CAPPED]
+      database.read_command(:collstats => name).documents[0][CAPPED]
     end
 
     # Force the collection to be created in the database.

lib/mongo/database.rb

@@ -159,6 +159,37 @@ def collections
     #
     # @return [ Hash ] The result of the command execution.
     def command(operation, opts = {})
+      txn_read_pref = if opts[:session] && opts[:session].in_transaction?
+        opts[:session].txn_read_preference
+      else
+        nil
+      end
+      txn_read_pref ||= opts[:read] || ServerSelector::PRIMARY
+      Lint.validate_underscore_read_preference(txn_read_pref)
+      selector = ServerSelector.get(txn_read_pref)
+
+      client.send(:with_session, opts) do |session|
+        server = selector.select_server(cluster, nil, session)
+        Operation::Command.new({
+          :selector => operation.dup,
+          :db_name => name,
+          :read => selector,
+          :session => session
+        }).execute(server)
+      end
+    end
+
+    # Execute a read command on the database, retrying the read if necessary.
+    #
+    # @param [ Hash ] operation The command to execute.
+    # @param [ Hash ] opts The command options.
+    #
+    # @option opts :read [ Hash ] The read preference for this command.
+    # @option opts :session [ Session ] The session to use for this command.
+    #
+    # @return [ Hash ] The result of the command execution.
+    # @api private
+    def read_command(operation, opts = {})
       txn_read_pref = if opts[:session] && opts[:session].in_transaction?
         opts[:session].txn_read_preference
       else

spec/integration/retryable_writes_spec.rb

@@ -737,4 +737,21 @@
 
     it_behaves_like 'an operation that does not support retryable writes'
   end
+
+  context 'when the operation is database#command' do
+
+    let(:operation) do
+      collection.database.command(ping: 1)
+    end
+
+    let(:expectation) do
+      0
+    end
+
+    let(:unsuccessful_retry_value) do
+      0
+    end
+
+    it_behaves_like 'an operation that does not support retryable writes'
+  end
 end