Skywalking对Nginx进行监控

Posted 2022-01-28 恒奇恒毅

本文基于Skywalking-8.7.0和nginx-1.20.1
书接上回，Skywalking已经能对Java应用非常轻松地接入监控，典型应用中，系统都是在负载均衡器后端跑JavaWeb应用，而最常用的负载均衡器就是Nginx。如果我们想把也纳入监控，该怎么办呢？幸运的是，Skywalking已经提供了Nginx的探针收集器。官网地址：https://github.com/apache/skywalking-nginx-lua。集成过程中发现，官网的例子只支持了OpenResty，对于OpenResty来说，已经集成了LuaJIT和lua-nginx-module等常用模块，按照官网的例子添加Skywalking相关的配置即可生效。但是配置给Nginx启动的时候就会报很多错误。我们可能并不想为了接入Skywalking就去换一个负载均衡器（Nginx换成OpenResty），如此，我们必须解决Skywalking与Nginx的集成问题。
备注：Openresty是基于Nginx+Lua的高性能Web开发平台，解决了Nginx不易编程的短板。

• Nginx的升级：

Nginx的agent插件是基于Lua来编写的，所以需要Nginx增加对Lua的支持，lua-nginx-module刚好提供了此功能。而lua-nginx-module依赖于LuaJIT,所以首先我们需要安装LuaJIT在环境中，最好选择2.1版本。

对Nginx来说，需要自己编译必须的模块。依赖以下两个模块：
lua-nginx-module，版本使用lua-nginx-module-0.10.21rc1
ngx_devel_kit，版本使用ngx_devel_kit-0.3.1
编译nginx参数

configure arguments: --add-module=/path/to/ngx_devel_kit-0.3.1 --add-module=/path/to/lua-nginx-module-0.10.21rc1 --with-ld-opt=-Wl,-rpath,/usr/local/LuaJIT/lib

下面针对skywalking-nginx-lua-0.3.0和0.3.0以上版本分别说明。

• skywalking-nginx-lua-0.3.0

经过测试，skywalking-nginx-lua-0.3.0需要以下lua相关模块

lua-resty-core  https://github.com/openresty/lua-resty-core
lua-resty-lrucache https://github.com/openresty/lua-resty-lrucache
lua-cjson https://github.com/openresty/lua-cjson

依赖的lua模块如下：

lua_package_path "/path/to/lua-resty-core/lua-resty-core-master/lib/?.lua;/path/to/lua-resty-lrucache-0.11/lib/?.lua;/path/to/skywalking-nginx-lua-0.3.0/lib/?.lua;;";

lua-cjson在make && make install过程中，有个需要注意的地方：
修改Makefile中一个路径
LUA_INCLUDE_DIR ?= /usr/local/LuaJIT/include/luajit-2.0
参考：https://blog.csdn.net/ymeputer/article/details/50146143

• skywalking-nginx-lua-0.3.0以上版本
  skywalking-nginx-lua-0.3.0以上版本需要添加tablepool的支持，但貌似不需要cjson

lua-resty-core  https://github.com/openresty/lua-resty-core
lua-resty-lrucache https://github.com/openresty/lua-resty-lrucache
lua-tablepool https://github.com/openresty/lua-tablepool

 lua_package_path "/path/to/lua-resty-core/lua-resty-core-master/lib/?.lua;/path/to/lua-resty-lrucache-0.11/lib/?.lua;/path/to/lua-tablepool-master/lib/?.lua;/path/to/skywalking-nginx-lua-master/lib/?.lua;;";

其中tablepool根据其官方文档介绍其中的两个APItable.new and table.clear需要LuaJIT2.1版本，在skywalking-nginx-lua的文档中有一段话，说可以通过require("skywalking.util").disable_tablepool()禁用tablepool

在启动nginx的时候，会有个提示，提示安装OpenResty自己的LuaJIT版本

detected a LuaJIT version which is not OpenResty's; many optimizations will be disabled and performance will be compromised (see https://github.com/openresty/luajit2 for OpenResty's LuaJIT or, even better, consider using the OpenResty releases from https://openresty.org/en/download.html)

下面给出调试成功的配置

     http 
    lua_package_path "/path/to/lua-resty-core/lua-resty-core-master/lib/?.lua;/path/to/lua-resty-lrucache-0.11/lib/?.lua;/path/to/lua-tablepool-master/lib/?.lua;/path/to/skywalking-nginx-lua-master/lib/?.lua;;";

    # Buffer represents the register inform and the queue of the finished segment
    lua_shared_dict tracing_buffer 100m;

    # Init is the timer setter and keeper
    # Setup an infinite loop timer to do register and trace report.
    init_worker_by_lua_block 
        local metadata_buffer = ngx.shared.tracing_buffer

        -- Set service name
        metadata_buffer:set('serviceName', 'User Service Name')
        -- Instance means the number of Nginx deployment, does not mean the worker instances
        metadata_buffer:set('serviceInstanceName', 'User Service Instance Name')
        -- type 'boolean', mark the entrySpan include host/domain
        metadata_buffer:set('includeHostInEntrySpan', false)

        -- set random seed
        require("skywalking.util").set_randomseed()
        require("skywalking.client"):startBackendTimer("http://127.0.0.1:12800")

        -- If there is a bug of this `tablepool` implementation, we can
        -- disable it in this way
        -- require("skywalking.util").disable_tablepool()

        skywalking_tracer = require("skywalking.tracer")
    

    server 
        listen 8090;
        
        location /ingress 
            default_type text/html;

            rewrite_by_lua_block 
                ------------------------------------------------------
                -- NOTICE, this should be changed manually
                -- This variable represents the upstream logic address
                -- Please set them as service logic name or DNS name
                --
                -- Currently, we can not have the upstream real network address
                ------------------------------------------------------
                skywalking_tracer:start("upstream service")
                -- If you want correlation custom data to the downstream service
                -- skywalking_tracer:start("upstream service", custom = "custom_value")
            

            -- Target upstream service
            proxy_pass http://127.0.0.1:8080/backend;

            body_filter_by_lua_block 
                if ngx.arg[2] then
                    skywalking_tracer:finish()
                end
            

            log_by_lua_block 
                skywalking_tracer:prepareForReport()
            
        
    

参考：https://www.cnblogs.com/kebibuluan/p/14440228.html