modern terminology

lib/sidekiq.rb

@@ -96,8 +96,8 @@ def self.redis
       begin
         yield conn
       rescue Redis::CommandError => ex
-        #2550 Failover can cause the server to become a slave, need
-        # to disconnect and reopen the socket to get back to the master.
+        #2550 Failover can cause the server to become a replica, need
+        # to disconnect and reopen the socket to get back to the primary.
         (conn.disconnect!; retryable = false; retry) if retryable && ex.message =~ /READONLY/
         raise
       end

test/test_sidekiq.rb

@@ -82,7 +82,7 @@ class TestSidekiq < Minitest::Test
     it 'does not continually retry' do
       assert_raises Redis::CommandError do
         Sidekiq.redis do |c|
-          raise Redis::CommandError, "READONLY You can't write against a read only slave."
+          raise Redis::CommandError, "READONLY You can't write against a replica."
         end
       end
     end
@@ -91,7 +91,7 @@ class TestSidekiq < Minitest::Test
       counts = []
       Sidekiq.redis do |c|
         counts << c.info['total_connections_received'].to_i
-        raise Redis::CommandError, "READONLY You can't write against a read only slave." if counts.size == 1
+        raise Redis::CommandError, "READONLY You can't write against a replica." if counts.size == 1
       end
       assert_equal 2, counts.size
       assert_equal counts[0] + 1, counts[1]