This was an important information missing from the INFO output in the
replication section.
It obviously reflects if the slave is read only or not.
                     (long)server.unixtime-server.repl_down_since);
             }
             info = sdscatprintf(info,
-                "slave_priority:%d\r\n", server.slave_priority);
+                "slave_priority:%d\r\n"
+                "slave_read_only:%d\r\n",
+                server.slave_priority,
+                server.repl_slave_ro);
         }
         info = sdscatprintf(info,
             "connected_slaves:%lu\r\n",