【高级技巧】监控告警台：多维指标的统一面板封装

local metrics = {}
local alertPanel = {}
local function registerMetric(name, collectFn, threshold, cmp)
    metrics[name] = { collect = collectFn, threshold = threshold,
        cmp = cmp, lastAlert = 0 }
end
local function scanMetrics()
    local now = os.time()
    for name, m in pairs(metrics) do
        local v = m.collect()
        local bad = m.cmp == "gt" and v > m.threshold
            or v < m.threshold
        if bad then
            local a = alertPanel[name]
            if a == nil or now - a.lastTs >= 300 then
                alertPanel[name] = { value = v, cnt = 1, lastTs = now }
                print("[告警] " .. name .. "=" .. v)
            else
                a.cnt = a.cnt + 1
                a.value = v
            end
        end
    end
end

registerMetric("error_rate", function()
    return errorRate()
end, 2, "gt")
registerMetric("online", function()
    return currentOnline()
end, 300, "lt")