【基于skyent的热更思考】

基于skyent的热更思考

skynet-inject热更原理
关键源码分析
热更方式
拓扑图
注意事项

skynet-inject热更原理

inject是一个用于动态加载 Lua 代码文件并执行其中定义的函数的功能。可以在运行时动态加载 Lua 代码文件，然后调用其中定义的函数，通过修改模块及其函数的upvalue，实现代码的动态注入和执行。热更实现的大概思路：通过向指定服务注入cmd实现热更
参考wiki https://blog.codingnow.com/2016/11/lua_update.html

关键源码分析

-- debug_console.lua

local function adjust_address(address)
    local prefix = address:sub(1,1)
    if prefix == '.' then
        return assert(skynet.localname(address), "Not a valid name")
    elseif prefix ~= ':' then
        address = assert(tonumber("0x" .. address), "Need an address") | (skynet.harbor(skynet.self()) << 24)
    end
    return address
end


function COMMAND.inject(address, filename, ...)
    address = adjust_address(address)
    local f = io.open(filename, "rb")
    if not f then
        return "Can't open " .. filename
    end
    local source = f:read "*a"
    f:close()
    local ok, output = skynet.call(address, "debug", "RUN", source, filename, ...)
    if ok == false then
        error(output)
    end
    return output
end

adjust_address: 用于调整传入的地址参数，对传入的地址参数进行转换,以保证将热更脚本注入到正确的服务地址
io.open(filename, “rb”): 以二进制只读的方式读取文件内容
source: 存放读取到的热更脚本内容
skynet.call(address, “debug”, “RUN”, …): 通过skynet的debug消息类型，将读取的热更脚本内容注入到目标服务地址(debug.RUN内部实现)

-- skynet.debug.lua

function dbgcmd.RUN(source, filename, ...)
    local inject = require "skynet.inject"
    local args = table.pack(...)
    local ok, output = inject(skynet, source, filename, args, export.dispatch, skynet.register_protocol)
    collectgarbage "collect"
    skynet.ret(skynet.pack(ok, table.concat(output, "\n")))
end

-- skynet.inject.lua

return function(skynet, source, filename, args, ...)
    if filename then
        filename = "@" .. filename
    else
        filename = "=(load)"
    end
    local output = {}

    local function print(...)
        local value = { ... }
        for k,v in ipairs(value) do
            value[k] = tostring(v)
        end
        table.insert(output, table.concat(value, "\t"))
    end
    local u = {}
    local unique = {}
    local funcs = { ... }
    for k, func in ipairs(funcs) do
        getupvaluetable(u, func, unique)
    end
    local p = {}
    local proto = u.proto
    if proto then
        for k,v in pairs(proto) do
            local name, dispatch = v.name, v.dispatch
            if name and dispatch and not p[name] then
                local pp = {}
                p[name] = pp
                getupvaluetable(pp, dispatch, unique)
            end
        end
    end
    local env = setmetatable( { print = print , _U = u, _P = p}, { __index = _ENV })
    local func, err = load(source, filename, "bt", env)
    if not func then
        return false, { err }
    end
    local ok, err = skynet.pcall(func, table.unpack(args, 1, args.n))
    if not ok then
        table.insert(output, err)
        return false, output
    end

    return true, output
end