Trace function call time

ftrace-example.lua

local TOO_LONG_CALL_THRESHOLD = 0.1

local log = require('log')
local clock = require 'clock'
local json = require 'json'.new() json.cfg{ encode_use_tostring = true }

local function ftail(fname, args, start, ...)
	local run = clock.realtime() - start
	if run > TOO_LONG_CALL_THRESHOLD then
		log.info("Function call %s(%s) was too long: %0.2fs", fname, json.encode(args), run)
	end
	return ...
end

local function ftrace(fname, func)
	return function(...)
		local start = clock.realtime()
		return ftail(fname, {...}, start, func(...))
	end
end

local function apply_ftrace(name, namespace)
	for fname, v in pairs(namespace) do
		if type(v) == 'table' then
			apply_ftrace(name .. '.' .. fname, v)
		elseif type(v) == 'function' and v ~= ftrace then
			namespace[fname] = ftrace(name .. '.' .. fname, v)
		end
	end
end

--[[

Use as

	apply_trace('', _G)

or to specific namespace

	apply_trace('app', app)

]]