--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_measure_storage/mod_measure_storage.lua	Wed Aug 31 16:24:32 2016 +0100
@@ -0,0 +1,56 @@
+module:set_global()
+
+local function return_args_after_calling(f, ...)
+	f();
+	return ...
+end
+
+local function time_method(module, store_name, store_type, method_name, method_function)
+	local opt_use_tags = module:get_option_boolean("measure_storage_tagged_metric", false);
+
+	local metric_name, metric_tags;
+	if opt_use_tags then
+		metric_name, metric_tags = "storage_operation", ("store_name:%s,store_type:%s,store_operation:%s"):format(store_name, store_type, method_name);
+	else
+		metric_name = store_name.."_"..store_type.."_"..method_name;
+	end
+	local measure_operation_started = module:measure(metric_name, metric_tags);
+
+	return function (...)
+		module:log("debug", "Measuring storage operation %s (%s)", metric_name, metric_tags or "no tags");
+		local measure_operation_complete = measure_operation_started();
+		return return_args_after_calling(measure_operation_complete, method_function(...));
+	end;
+end
+
+local function wrap_store(module, store_name, store_type, store)
+	local new_store = setmetatable({}, {
+		__index = function (t, method_name)
+			local original_method = store[method_name];
+			if type(original_method) ~= "function" then
+				if original_method then
+					rawset(t, method_name, original_method);
+				end
+				return original_method;
+			end
+			local timed_method = time_method(module, store_name, store_type, method_name, original_method);
+			rawset(t, method_name, timed_method);
+			return timed_method;
+		end;
+	});
+	return new_store;
+end
+
+local function hook_event(module)
+	module:hook("store-opened", function(event)
+		event.store = wrap_store(module, event.store_name, event.store_type, event.store);
+	end);
+end
+
+function module.load()
+	hook_event(module);
+end
+
+function module.add_host(module)
+	hook_event(module);
+end