Add module parameter options

The options allow the modules to impose type specific restrictions on the
parameters. This can be used to offload file permission and mandatory
parameter checks to the core.

server/core/config.c

@@ -1913,6 +1913,38 @@ process_config_update(CONFIG_CONTEXT *context)
     return true;
 }
 
+/**
+ * @brief Check if required parameters are missing
+ *
+ * @param name Module name
+ * @param type Module type
+ * @param params List of parameters for the object
+ * @return True if at least one of the required parameters is missing
+ */
+static bool missing_required_parameters(const char *name, const char *type,
+                                        CONFIG_PARAMETER *params)
+{
+    bool rval = false;
+
+    const MXS_MODULE *mod = get_module(name, type);
+
+    if (mod)
+    {
+        for (int i = 0; mod->parameters[i].name; i++)
+        {
+            if ((mod->parameters[i].options & MXS_MODULE_OPT_REQUIRED) &&
+                config_get_param(params, mod->parameters[i].name) == NULL)
+            {
+                MXS_ERROR("Mandatory parameter '%s' for module '%s' of type %s is not defined.",
+                          mod->parameters[i].name, name, type);
+                rval = true;
+            }
+        }
+    }
+
+    return rval;
+}
+
 /**
  * @brief Check that the configuration objects have valid parameters
  *
@@ -1986,6 +2018,13 @@ check_config_objects(CONFIG_CONTEXT *context)
                 params = params->next;
             }
         }
+
+        if (module && module_type &&
+            missing_required_parameters(module, module_type, obj->parameters))
+        {
+            rval = false;
+        }
+
         obj = obj->next;
     }
 
@@ -2628,12 +2667,15 @@ static void config_add_defaults(CONFIG_CONTEXT *ctx, const char *module, const c
     {
         for (int i = 0; mod->parameters[i].name; i++)
         {
-            ss_dassert(config_param_is_valid(module, type, mod->parameters[i].name,
-                                             mod->parameters[i].default_value));
+            if (mod->parameters[i].default_value)
+            {
+                ss_dassert(config_param_is_valid(module, type, mod->parameters[i].name,
+                                                 mod->parameters[i].default_value, ctx));
 
-            bool rv = config_add_param(ctx, mod->parameters[i].name,
-                                       mod->parameters[i].default_value);
-            MXS_ABORT_IF_FALSE(rv);
+                bool rv = config_add_param(ctx, mod->parameters[i].name,
+                                           mod->parameters[i].default_value);
+                MXS_ABORT_IF_FALSE(rv);
+            }
         }
     }
 }