【网络通信】服务发现：动态扩容的节点注册

local ALL_NODES = { "node_a", "node_b", "node_c", "node_d", "node_e" }
setontimerex(203, 60)
function ontimer203()
    local now = os.time()
    local live = {}
    for _, nodeId in ipairs(ALL_NODES) do
        local ts = tonumber(getsysvar("NODE_HB_" .. nodeId) or "0")
        if now - ts <= 180 then
            live[#live + 1] = nodeId
        end
    end
    setsysvarex("NODE_LIVE", table.concat(live, ","), 1)
end

local function pickNode()
    local live = {}
    for nodeId in string.gmatch(getsysvar("NODE_LIVE") or "", "[^,]+") do
        table.insert(live, nodeId)
    end
    if #live == 0 then
        sendmail("#运维老张", 935, "服务发现告警", "存活节点清单为空，请立即检查跨服节点", "")
        return nil
    end
    return live[math.random(#live)]
end