【高级技巧】熔断器：连续失败的快速失败封装

local function createBreaker(threshold, coolSec)
    local fails, openedAt = 0, 0
    local THRESHOLD, COOL = threshold, coolSec
    return {
        call = function(fn)
            if openedAt > 0 and os.time() - openedAt < COOL then
                return false, "circuit-open"
            end
            if openedAt > 0 then
                openedAt = 0
                fails = 0
            end
            local ok = fn()
            if ok then
                fails = 0
                return true
            end
            fails = fails + 1
            if fails >= THRESHOLD then
                openedAt = os.time()
            end
            return ok
        end,
    }
end
local mailBreaker = createBreaker(5, 30)

local function safeSendMail(actor, ticket)
    actor = getplayerbyname(actor)
    local ok, why = mailBreaker.call(function()
        sendmail("#" .. tostring(actor), 9080, "奖励补发",
            "补发单[" .. ticket .. "]。", "金条#1#0")
        return true
    end)
    if not ok then
        sendmsg(actor, 1, "补发延迟中：邮件通道" ..
            (why == "circuit-open" and "熔断保护" or "异常") .. "。")
    end
end