Apisix 源码分析以及手撸一个简单版本的 Apisix

APISIX 概述

APISIX 与 Kong 类似，是一个基于 OpenResty 构建的 API 网关,APISIX 不同于 Kong 的地方，例如 etcd 数据变化监听、强大的缓存机制、以及在性能优化上做的尝试。

项目概述

APISIX 是基于 OpenResty 开发的 API 网关，与 OpenResty 的请求生命周期一致，APISIX 利用 Lua Nginx Module 提供的 *_by_lua 添加 Hook

APISIX 抽象了 Route、Service、Upstream、Plugin、Consumer 等数据模型，与 Kong 网关如出一辙。


基本上可以看作 APISIX 是 Kong 网关的重构——运用大量 LuaJIT、OpenResty 技巧优化性能、简化复杂的数据结构、替换储存引擎为 etcd 等。

生态概述

Kong 网关开源生态有的，APISIX 基本都有或者正在做。包含：Kubernetes Ingress Controller、Mesh、Dashboard。
插件方面比 Kong 开源版本多了 Skywalking APM 数据上报、Traffit 流量拆分、Mirror 流量镜像等功能。

阅读源码目的

1. 对一个项目有着全局思维，遇到问题能快速找到关联点
2. 克服心里障碍，遇到坑后查阅各种资料无果

什么时候开始阅读源码

对这个开源项目使用已经很熟练了，用来解决什么问题，设计思想都比较清楚的前提下

源码分析方法论

1. 整体模块结构
2. 找到启动类
3. 分清主干和枝节代码
4. 充分利用源码项目的测试类
5. 要学会一些调试技巧
6. 看 git 提交记录，寻找最小版 demo
7. 带着问题去思考
8. 和开发人员直接沟通

基本流程

本节概述 APISIX 的目录结构，以及其启动流程。

目录结构

$ tree -L 2
.
├── apisix
│   ├── admin # Admin API
│   ├── api_router.lua
│   ├── balancer # 负载均衡器
│   ├── balancer.lua
│   ├── cli # CLI, Lua 脚本
│   ├── constants.lua # 常量
│   ├── consumer.lua
│   ├── control
│   ├── core # 主要是封装的公共方法
│   ├── core.lua
│   ├── debug.lua
│   ├── discovery # 服务发现, 支持 consul, eruka, dns
│   ├── http
│   ├── init.lua # _by_lua 函数入口
│   ├── patch.lua
│   ├── plugin_config.lua
│   ├── plugin.lua # 插件
│   ├── plugins
│   ├── router.lua # Router
│   ├── schema_def.lua # jsonschema 定义
│   ├── script.lua
│   ├── ssl
│   ├── ssl.lua
│   ├── stream
│   ├── timers.lua # timer 封装
│   ├── upstream.lua
│   └── utils
├── bin
│   └── apisix # apisix CLI, shell 脚本
├── ci # CI 脚本
├── conf # 默认配置文件
├── deps
├── docs
├── Makefile # 快捷指令
├── rockspec # luarocks 包管理
├── t # Test::Nginx 测试
└── utils # Shell 脚本

启动流程

• make run 调用 ./bin/apisix start
• 寻找 luajit 路径 运行 /usr/local/Cellar/openresty/1.19.9.1_2/luajit/bin/luajit ./apisix/cli/apisix.lua start
• 调用 ops.lua 里的 start 方法,初始化配置，ETCD，执行openresty 启动命令

local function start(env, ...)
    init(env)
    init_etcd(env, args)
    util.execute_cmd(env.openresty_args)
end

• 初始化 nginx 配置，通过读取 conf/config.yaml 配合模板 ngx_tpl.lua 生成 nginx config 文件。供 openresty(nginx)使用

 local conf_render = template.compile(ngx_tpl)
    local ngxconf = conf_render(sys_conf)

    local ok, err = util.write_file(env.apisix_home .. "/conf/nginx.conf",
                                    ngxconf)
    if not ok then
        util.die("failed to update nginx.conf: ", err, "\n")
    end

• 初始化 ETCD,读取ETCD集群配置，进行连接

local version_url = host .. "/version"
        local errmsg

        local res, err
        local retry_time = 0
        while retry_time < 2 do
            res, err = request(version_url, yaml_conf)
            -- In case of failure, request returns nil followed by an error message.
            -- Else the first return value is the response body
            -- and followed by the response status code.
            if res then
                break
            end
            retry_time = retry_time + 1
            print(str_format("Warning! Request etcd endpoint \'%s\' error, %s, retry time=%s",
                             version_url, err, retry_time))
        end

• 执行openresty 启动命令 openresty -p /usr/local/apisix -c /conf/nginx.conf

    local openresty_args = [[openresty -p ]] .. apisix_home .. [[ -c ]]
                           .. apisix_home .. [[/conf/nginx.conf]]

    util.execute_cmd(env.openresty_args)

插件流程

nginx 配置中嵌入的 apisix 流程

 init_by_lua_block {
        require "resty.core"
        apisix = require("apisix")

        local dns_resolver = { "172.19.2.70", "172.19.2.62", }
        local args = {
            dns_resolver = dns_resolver,
        }
        apisix.http_init(args)
}
    
init_worker_by_lua_block {
        apisix.http_init_worker()
}

exit_worker_by_lua_block {
        apisix.http_exit_worker()
}

access_by_lua_block {
                apisix.http_access_phase()
}
header_filter_by_lua_block {
                apisix.http_header_filter_phase()
}
body_filter_by_lua_block {
                apisix.http_body_filter_phase()
}
log_by_lua_block {
                apisix.http_log_phase()
}

proxy_pass      $upstream_scheme://apisix_backend$upstream_uri;

upstream apisix_backend {
        server 0.0.0.1;

        balancer_by_lua_block {
            apisix.http_balancer_phase()
        }

        keepalive 320;
        keepalive_requests 1000;
        keepalive_timeout 60s;
}

• apisix.http_init
  1.设置 dns resolver
  2.设置实例id
  3.启动 privileged agent

    core.resolver.init_resolver(args)
    core.id.init()
    local process = require("ngx.process")
    local ok, err = process.enable_privileged_agent()

• apisix.http_init_worker

function _M.http_init_worker()
    local seed, err = core.utils.get_seed_from_urandom()
    if not seed then
        core.log.warn('failed to get seed from urandom: ', err)
        seed = ngx_now() * 1000 + ngx.worker.pid()
    end
    math.randomseed(seed)
    -- for testing only
    core.log.info("random test in [1, 10000]: ", math.random(1, 10000))

    local we = require("resty.worker.events")
    local ok, err = we.configure({shm = "worker-events", interval = 0.1})
    if not ok then
        error("failed to init worker event: " .. err)
    end
    local discovery = require("apisix.discovery.init").discovery
    if discovery and discovery.init_worker then
        discovery.init_worker()
    end
    require("apisix.balancer").init_worker()
    load_balancer = require("apisix.balancer")
    require("apisix.admin.init").init_worker()

    require("apisix.timers").init_worker()

    plugin.init_worker()
    router.http_init_worker()
    require("apisix.http.service").init_worker()
    plugin_config.init_worker()
    require("apisix.consumer").init_worker()

    if core.config == require("apisix.core.config_yaml") then
        core.config.init_worker()
    end

    require("apisix.debug").init_worker()
    apisix_upstream.init_worker()
    require("apisix.plugins.ext-plugin.init").init_worker()

    local_conf = core.config.local_conf()

    if local_conf.apisix and local_conf.apisix.enable_server_tokens == false then
        ver_header = "APISIX"
    end
end

1.初始化 openresty worker event

    local we = require("resty.worker.events")
    local ok, err = we.configure({shm = "worker-events", interval = 0.1})
    if not ok then
        error("failed to init worker event: " .. err)
    end

2.初始化服务发现
3.初始化balancer组件
4.初始化admin组件（会同步一次插件配置到 etcd）

     sync_local_conf_to_etcd(true)

5.初始化timers组件
6.初始化 plugin 组件(清掉旧的 table, 然后把从config-default.yaml 和 config.yaml 文件中读取插件配置放到一个 local_plugins_hash中，并按优先级排序)

local local_conf_path = profile:yaml_path("config-default")
local default_conf_yaml, err = util.read_file(local_conf_path)
local_conf_path = profile:yaml_path("config")
local user_conf_yaml, err = util.read_file(local_conf_path)
 ok, err = merge_conf(default_conf, user_conf)


 local local_plugins = core.table.new(32, 0)

  for name in pairs(local_plugins_hash) do
        unload_plugin(name)
    end

    core.table.clear(local_plugins)
    core.table.clear(local_plugins_hash)

    for name in pairs(processed) do
        load_plugin(name, local_plugins)
    end

    -- sort by plugin's priority
    if #local_plugins > 1 then
        sort_tab(local_plugins, sort_plugin)
    end

    local plugin_metadatas, err = core.config.new("/plugin_metadata",
        {automatic = true}
    )

7.初始化router组件（初始化 etcd /global_rules 数据）

    local global_rules, err = core.config.new("/global_rules", {
            automatic = true,
            item_schema = core.schema.global_rule,
            checker = plugin_checker,
        })

8.初始化 servers 组件(从ETCD抓取 services 配置)

services, err = core.config.new("/services", {
        automatic = true,
        item_schema = core.schema.service,
        checker = plugin_checker,
        filter = filter,
    })

9.初始化sonsumer组件
10.同步 config_yaml 到各个进程

    -- sync data in each non-master process
    ngx.timer.every(1, read_apisix_yaml)

11.初始化upstream组件
12.初始化 ext-plugin 组件

• apisix.http_exit_worker()
  停止 "privileged agent"
• apisix.http_access_phase()

function _M.http_access_phase()
    local ngx_ctx = ngx.ctx

    if not verify_tls_client(ngx_ctx.api_ctx) then
        return core.response.exit(400)
    end

    -- always fetch table from the table pool, we don't need a reused api_ctx
    local api_ctx = core.tablepool.fetch("api_ctx", 0, 32)
    ngx_ctx.api_ctx = api_ctx

    core.ctx.set_vars_meta(api_ctx)

    local uri = api_ctx.var.uri
    if local_conf.apisix and local_conf.apisix.delete_uri_tail_slash then
        if str_byte(uri, #uri) == str_byte("/") then
            api_ctx.var.uri = str_sub(api_ctx.var.uri, 1, #uri - 1)
            core.log.info("remove the end of uri '/', current uri: ",
                          api_ctx.var.uri)
        end
    end

    if router.api.has_route_not_under_apisix() or
        core.string.has_prefix(uri, "/apisix/")
    then
        local skip = local_conf and local_conf.apisix.global_rule_skip_internal_api
        local matched = router.api.match(api_ctx, skip)
        if matched then
            return
        end
    end

    router.router_http.match(api_ctx)

    local route = api_ctx.matched_route
    if not route then
        -- run global rule
        plugin.run_global_rules(api_ctx, router.global_rules, nil)

        core.log.info("not find any matched route")
        return core.response.exit(404,
                    {error_msg = "404 Route Not Found"})
    end

    core.log.info("matched route: ",
                  core.json.delay_encode(api_ctx.matched_route, true))

    local enable_websocket = route.value.enable_websocket

    if route.value.plugin_config_id then
        local conf = plugin_config.get(route.value.plugin_config_id)
        if not conf then
            core.log.error("failed to fetch plugin config by ",
                            "id: ", route.value.plugin_config_id)
            return core.response.exit(503)
        end

        route = plugin_config.merge(route, conf)
    end

    if route.value.service_id then
        local service = service_fetch(route.value.service_id)
        if not service then
            core.log.error("failed to fetch service configuration by ",
                           "id: ", route.value.service_id)
            return core.response.exit(404)
        end

        route = plugin.merge_service_route(service, route)
        api_ctx.matched_route = route
        api_ctx.conf_type = "route&service"
        api_ctx.conf_version = route.modifiedIndex .. "&" .. service.modifiedIndex
        api_ctx.conf_id = route.value.id .. "&" .. service.value.id
        api_ctx.service_id = service.value.id
        api_ctx.service_name = service.value.name

        if enable_websocket == nil then
            enable_websocket = service.value.enable_websocket
        end

    else
        api_ctx.conf_type = "route"
        api_ctx.conf_version = route.modifiedIndex
        api_ctx.conf_id = route.value.id
    end
    api_ctx.route_id = route.value.id
    api_ctx.route_name = route.value.name

    -- run global rule
    plugin.run_global_rules(api_ctx, router.global_rules, nil)

    if route.value.script then
        script.load(route, api_ctx)
        script.run("access", api_ctx)

    else
        local plugins = plugin.filter(route)
        api_ctx.plugins = plugins

        plugin.run_plugin("rewrite", plugins, api_ctx)
        if api_ctx.consumer then
            local changed
            route, changed = plugin.merge_consumer_route(
                route,
                api_ctx.consumer,
                api_ctx
            )

            core.log.info("find consumer ", api_ctx.consumer.username,
                          ", config changed: ", changed)

            if changed then
                api_ctx.matched_route = route
                core.table.clear(api_ctx.plugins)
                api_ctx.plugins = plugin.filter(route, api_ctx.plugins)
            end
        end
        plugin.run_plugin("access", plugins, api_ctx)
    end

    local up_id = route.value.upstream_id

    -- used for the traffic-split plugin
    if api_ctx.upstream_id then
        up_id = api_ctx.upstream_id
    end

    if up_id then
        local upstream = get_upstream_by_id(up_id)
        api_ctx.matched_upstream = upstream

    else
        if route.has_domain then
            local err
            route, err = parse_domain_in_route(route)
            if err then
                core.log.error("failed to get resolved route: ", err)
                return core.response.exit(500)
            end

            api_ctx.conf_version = route.modifiedIndex
            api_ctx.matched_route = route
        end

        local route_val = route.value
        if route_val.upstream and route_val.upstream.enable_websocket then
            enable_websocket = true
        end

        api_ctx.matched_upstream = (route.dns_value and
                                    route.dns_value.upstream)
                                   or route_val.upstream
    end

    if enable_websocket then
        api_ctx.var.upstream_upgrade    = api_ctx.var.http_upgrade
        api_ctx.var.upstream_connection = api_ctx.var.http_connection
        core.log.info("enabled websocket for route: ", route.value.id)
    end

    if route.value.service_protocol == "grpc" then
        api_ctx.upstream_scheme = "grpc"
    end

    local code, err = set_upstream(route, api_ctx)
    if code then
        core.log.error("failed to set upstream: ", err)
        core.response.exit(code)
    end

    local server, err = load_balancer.pick_server(route, api_ctx)
    if not server then
        core.log.error("failed to pick server: ", err)
        return core.response.exit(502)
    end

    api_ctx.picked_server = server

    set_upstream_headers(api_ctx, server)

    -- run the before_proxy method in access phase first to avoid always reinit request
    common_phase("before_proxy")

    local ref = ctxdump.stash_ngx_ctx()
    core.log.info("stash ngx ctx: ", ref)
    ngx_var.ctx_ref = ref

    local up_scheme = api_ctx.upstream_scheme
    if up_scheme == "grpcs" or up_scheme == "grpc" then
        return ngx.exec("@grpc_pass")
    end

    if api_ctx.dubbo_proxy_enabled then
        return ngx.exec("@dubbo_pass")
    end
end

1.初始化 api_ctx 上下文
2.client tls 验证
3.是否为 apisix 已经注册的路径，对请求进行匹配，内部使用 Radix tree 进行匹配
4.向上下文注入该请求匹配的 apisix route ，service 等信息用于后续阶段使用
5.向上下文注入该请求相关的插件，例如：请求对应的路由存在插件，若请求存在对应的 service 则加入 service 定义的插件，以及全局插件
6.调用 "rewrite" 阶段的插件
7.调用 "access" 阶段的插件
8.获取 upstream
9.执行 loadbalancer 选择 server
10.调用 "balancer" 阶段插件
11.判断 upstream ，根据 upstream 类型，grpc dubbo 等进入 @grpc_pass @dubbo_pass 等不同的后续处理流程。 这些配置可在 nginx.conf 中查看

• apisix.http_balancer_phase()

function _M.http_header_filter_phase()
    if ngx_var.ctx_ref ~= '' then
        -- prevent for the table leak
        local stash_ctx = fetch_ctx()

        -- internal redirect, so we should apply the ctx
        if ngx_var.from_error_page == "true" then
            ngx.ctx = stash_ctx
        end
    end

    core.response.set_header("Server", ver_header)

    local up_status = get_var("upstream_status")
    if up_status and #up_status == 3
       and tonumber(up_status) >= 500
       and tonumber(up_status) <= 599
    then
        set_resp_upstream_status(up_status)
    elseif up_status and #up_status > 3 then
        -- the up_status can be "502, 502" or "502, 502 : "
        local last_status
        if str_byte(up_status, -1) == str_byte(" ") then
            last_status = str_sub(up_status, -6, -3)
        else
            last_status = str_sub(up_status, -3)
        end

        if tonumber(last_status) >= 500 and tonumber(last_status) <= 599 then
            set_resp_upstream_status(up_status)
        end
    end

    common_phase("header_filter")
end

1.设置头 "Server", APISIX
2.设置上游状态头：X-APISIX-Upstream-Status
3.执行 “header_filter” 阶段的插件

• apisix.http_body_filter_phase()

function _M.http_body_filter_phase()
    common_phase("body_filter")
end

执行 “body_filter” 阶段的插件

• apisix.http_log_phase()

function _M.http_log_phase()
    if ngx_var.ctx_ref ~= '' then
        -- prevent for the table leak
        local stash_ctx = fetch_ctx()

        -- internal redirect, so we should apply the ctx
        if ngx_var.from_error_page == "true" then
            ngx.ctx = stash_ctx
        end
    end

    local api_ctx = common_phase("log")
    if not api_ctx then
        return
    end

    healthcheck_passive(api_ctx)

    if api_ctx.server_picker and api_ctx.server_picker.after_balance then
        api_ctx.server_picker.after_balance(api_ctx, false)
    end

    if api_ctx.uri_parse_param then
        core.tablepool.release("uri_parse_param", api_ctx.uri_parse_param)
    end

    core.ctx.release_vars(api_ctx)
    if api_ctx.plugins then
        core.tablepool.release("plugins", api_ctx.plugins)
    end

    if api_ctx.curr_req_matched then
        core.tablepool.release("matched_route_record", api_ctx.curr_req_matched)
    end

    core.tablepool.release("api_ctx", api_ctx)
end

1.执行 “log” 阶段的插件
2.回收 plugins, matched_route_record,api_ctx 缓存

• apisix.http_balancer_phase()

function _M.http_balancer_phase()
    local api_ctx = ngx.ctx.api_ctx
    if not api_ctx then
        core.log.error("invalid api_ctx")
        return core.response.exit(500)
    end

    load_balancer.run(api_ctx.matched_route, api_ctx, common_phase)
end

1.设置 balance 的基本参数（超时时间，连接失败重试次数）
2.选择上游服务器,采用一致性hash算法
3.调用 set_current_peer 设置 proxy_pass

自定义插件逻辑

通过 common_phase 作为自定义插件的方法的公共入口，被 openresty 各个环节调用

local function common_phase(phase_name)
    local api_ctx = ngx.ctx.api_ctx
    if not api_ctx then
        return
    end

    plugin.run_global_rules(api_ctx, api_ctx.global_rules, phase_name)

    if api_ctx.script_obj then
        script.run(phase_name, api_ctx)
        return api_ctx, true
    end

    return plugin.run_plugin(phase_name, nil, api_ctx)
end

真正执行自定义插件逻辑

 for i = 1, #plugins, 2 do
            local phase_func = plugins[i][phase]
            if phase_func then
                plugin_run = true
                local code, body = phase_func(plugins[i + 1], api_ctx)
                if code or body then
                    if is_http then
                        if code >= 400 then
                            core.log.warn(plugins[i].name, " exits with http status code ", code)
                        end

                        core.response.exit(code, body)
                    else
                        if code >= 400 then
                            core.log.warn(plugins[i].name, " exits with status code ", code)
                        end

                        ngx_exit(1)
                    end
                end
            end
        end

admin api

        location /apisix/admin {
            set $upstream_scheme             'http';
            set $upstream_host               $http_host;
            set $upstream_uri                '';

                allow 127.0.0.0/24;
                deny all;

            content_by_lua_block {
                apisix.http_admin()
            }
        }

自定义插件

入口

local function common_phase(phase_name)
    local api_ctx = ngx.ctx.api_ctx
    if not api_ctx then
        return
    end

    plugin.run_global_rules(api_ctx, api_ctx.global_rules, phase_name)

    if api_ctx.script_obj then
        script.run(phase_name, api_ctx)
        return api_ctx, true
    end

    return plugin.run_plugin(phase_name, nil, api_ctx)
end

已知的阶段
preread
ssl
access
balancer
rewrite
header_filter
body_filter
log

admin api

入口

        location /apisix/admin {
            set $upstream_scheme             'http';
            set $upstream_host               $http_host;
            set $upstream_uri                '';

                allow 127.0.0.0/24;
                deny all;

            content_by_lua_block {
                apisix.http_admin()
            }
        }

根据路由进行转发

    local ok = router:dispatch(get_var("uri"), {method = get_method()})

具体路由 dispatch 逻辑

function _M.dispatch(self, path, opts, ...)
    if type(path) ~= "string" then
        error("invalid argument path", 2)
    end

    local args
    local len = select('#', ...)
    if len > 0 then
        if not self.args then
            self.args = {...}
        else
            clear_tab(self.args)
            for i = 1, len do
                self.args[i] = select(i, ...)
            end
        end

        -- To keep the self.args in safe,
        -- we can't yield until filter_fun is called
        args = self.args
        args[0] = len
    end

    local route, err = match_route(self, path, opts or empty_table, args)
    if not route then
        if err then
            return nil, err
        end
        return nil
    end

    local handler = route.handler
    if not handler or type(handler) ~= "function" then
        return nil, "missing handler"
    end

    handler(...)
    return true
end

路由与hanlder 的关系

local uri_route = {
    {
        paths = [[/apisix/admin/*]],
        methods = {"GET", "PUT", "POST", "DELETE", "PATCH"},
        handler = run,
    },
    {
        paths = [[/apisix/admin/stream_routes/*]],
        methods = {"GET", "PUT", "POST", "DELETE", "PATCH"},
        handler = run_stream,
    },
    {
        paths = [[/apisix/admin/plugins/list]],
        methods = {"GET"},
        handler = get_plugins_list,
    },
    {
        paths = reload_event,
        methods = {"PUT"},
        handler = post_reload_plugins,
    },
}

调用 run 方法

local function run()
    local api_ctx = {}
    core.ctx.set_vars_meta(api_ctx)
    ngx.ctx.api_ctx = api_ctx

    local ok, err = check_token(api_ctx)
    if not ok then
        core.log.warn("failed to check token: ", err)
        core.response.exit(401)
    end

    local uri_segs = core.utils.split_uri(ngx.var.uri)
    core.log.info("uri: ", core.json.delay_encode(uri_segs))

    -- /apisix/admin/schema/route
    local seg_res, seg_id = uri_segs[4], uri_segs[5]
    local seg_sub_path = core.table.concat(uri_segs, "/", 6)
    if seg_res == "schema" and seg_id == "plugins" then
        -- /apisix/admin/schema/plugins/limit-count
        seg_res, seg_id = uri_segs[5], uri_segs[6]
        seg_sub_path = core.table.concat(uri_segs, "/", 7)
    end

    local resource = resources[seg_res]
    if not resource then
        core.response.exit(404)
    end

    local method = str_lower(get_method())
    if not resource[method] then
        core.response.exit(404)
    end

    local req_body, err = core.request.get_body(MAX_REQ_BODY)
    if err then
        core.log.error("failed to read request body: ", err)
        core.response.exit(400, {error_msg = "invalid request body: " .. err})
    end

    if req_body then
        local data, err = core.json.decode(req_body)
        if not data then
            core.log.error("invalid request body: ", req_body, " err: ", err)
            core.response.exit(400, {error_msg = "invalid request body: " .. err,
                                     req_body = req_body})
        end

        req_body = data
    end

    local uri_args = ngx.req.get_uri_args() or {}
    if uri_args.ttl then
        if not tonumber(uri_args.ttl) then
            core.response.exit(400, {error_msg = "invalid argument ttl: "
                                                 .. "should be a number"})
        end
    end

    local code, data = resource[method](seg_id, req_body, seg_sub_path,
                                        uri_args)
    if code then
        data = strip_etcd_resp(data)
        core.response.exit(code, data)
    end
end

根据 resource 定义找到对应的 lua 模板的执行方法

local resources = {
    routes          = require("apisix.admin.routes"),
    services        = require("apisix.admin.services"),
    upstreams       = require("apisix.admin.upstreams"),
    consumers       = require("apisix.admin.consumers"),
    schema          = require("apisix.admin.schema"),
    ssl             = require("apisix.admin.ssl"),
    plugins         = require("apisix.admin.plugins"),
    proto           = require("apisix.admin.proto"),
    global_rules    = require("apisix.admin.global_rules"),
    stream_routes   = require("apisix.admin.stream_routes"),
    plugin_metadata = require("apisix.admin.plugin_metadata"),
    plugin_configs  = require("apisix.admin.plugin_config"),
}

执行对应模块的对应的方法，例如：
GET http://127.0.0.1:9080/apisix/admin/plugin_metadata/whalefin-i18n
就是直接调用 plugin_metadata 的 get 方法

function _M.get(key)

    local path = "/plugin_metadata"
    if key then
        path = path .. "/" .. key
    end

    local res, err = core.etcd.get(path, not key)
    if not res then
        core.log.error("failed to get metadata[", key, "]: ", err)
        return 503, {error_msg = err}
    end

    return res.status, res.body
end

control api

入口 apisix.http_control()

server {
        listen 127.0.0.1:9090;

        access_log off;

        location / {
            content_by_lua_block {
                apisix.http_control()
            }
        }

        location @50x.html {
            set $from_error_page 'true';
            content_by_lua_block {
                require("apisix.error_handling").handle_500()
            }
        }
    }

先注册所有的插件的 control_api 方法，调用 router:dispatch 进行路由分发

function _M.match(uri)
    if cached_version ~= plugin_mod.load_times then
        local err
        router, err = fetch_control_api_router()
        if router == nil then
            core.log.error("failed to fetch valid api router: ", err)
            return false
        end

        cached_version = plugin_mod.load_times
    end

    core.table.clear(match_opts)
    match_opts.method = get_method()

    return router:dispatch(uri, match_opts)
end

例如：server_info 插件，注册路径 /v1/server_info 并指定使用 get_server_info函数进行处理

function _M.control_api()
    return {
        {
            methods = {"GET"},
            uris ={"/v1/server_info"},
            handler = get_server_info,
        }
    }
end

注册 plugin的 control_api 方法

    for _, plugin in ipairs(plugin_mod.plugins) do
        local api_fun = plugin.control_api
        if api_fun then
            local api_route = api_fun()
            register_api_routes(routes, api_route)
        end
    end

通过dispatch 方法调用插件的 handler 方法

   local route, err = match_route(self, path, opts or empty_table, args)
    if not route then
        if err then
            return nil, err
        end
        return nil
    end

    local handler = route.handler
    if not handler or type(handler) ~= "function" then
        return nil, "missing handler"
    end

    handler(...)