Cache formatters.

Instead of creating a formatter for each event, cache them and create
them only when needed. A new function output_cleanup cleans up the
cached formatters, and is called in the destructor if init() was called.

userspace/falco/falco_outputs.cpp

@@ -27,13 +27,28 @@ along with falco.  If not, see <http://www.gnu.org/licenses/>.
 using namespace std;
 
 falco_outputs::falco_outputs()
+	: m_initialized(false)
 {
 
 }
 
 falco_outputs::~falco_outputs()
 {
+	if(m_initialized)
+	{
+		lua_getglobal(m_ls, m_lua_output_cleanup.c_str());
 
+		if(!lua_isfunction(m_ls, -1))
+		{
+			throw falco_exception("No function " + m_lua_output_cleanup + " found. ");
+		}
+
+		if(lua_pcall(m_ls, 0, 0, 0) != 0)
+		{
+			const char* lerr = lua_tostring(m_ls, -1);
+			throw falco_exception(string(lerr));
+		}
+	}
 }
 
 void falco_outputs::init(bool json_output)
@@ -52,6 +67,8 @@ void falco_outputs::init(bool json_output)
 	falco_formats::init(m_inspector, m_ls, json_output);
 
 	falco_logger::init(m_ls);
+
+	m_initialized = true;
 }
 
 void falco_outputs::add_output(output_config oc)

userspace/falco/falco_outputs.h

@@ -51,7 +51,10 @@ public:
 	void handle_event(sinsp_evt *ev, std::string &level, std::string &priority, std::string &format);
 
 private:
+	bool m_initialized;
+
 	std::string m_lua_add_output = "add_output";
 	std::string m_lua_output_event = "output_event";
+	std::string m_lua_output_cleanup = "output_cleanup";
 	std::string m_lua_main_filename = "output.lua";
 };

userspace/falco/lua/output.lua

@@ -24,6 +24,8 @@ mod.levels = levels
 
 local outputs = {}
 
+local formatters = {}
+
 function mod.stdout(level, msg)
    print (msg)
 end
@@ -75,14 +77,26 @@ end
 function output_event(event, rule, priority, format)
    local level = level_of(priority)
    format = "*%evt.time: "..levels[level+1].." "..format
-   formatter = formats.formatter(format)
+   if formatters[rule] == nil then
+      formatter = formats.formatter(format)
+      formatters[rule] = formatter
+   else
+      formatter = formatters[rule]
+   end
+
    msg = formats.format_event(event, rule, levels[level+1], formatter)
 
    for index,o in ipairs(outputs) do
       o.output(level, msg, o.config)
    end
+end
 
-   formats.free_formatter(formatter)
+function output_cleanup()
+   for rule, formatter in pairs(formatters) do
+      formats.free_formatter(formatter)
+   end
+
+   formatters = {}
 end
 
 function add_output(output_name, config)