0. 需求

复制线上真实流量，在不影响真实业务前提下，利用复制流量来做故障分析、性能定位、迁移评估等功能。具体功能包含：

支持或禁止post请求复制
记录复制(镜像)日志

mirror：中文为镜像的意思，这里指流量复制的目的地。

1. ngx_http_mirror_module模块特性

nginx 1.13.4及后续版本内置ngx_http_mirror_module模块，提供流量镜像(复制)的功能。
支持流量放大，做法为：配置多份相同镜像。
相比tcp-copy的优势：无需录制流量，实时可用；配置相当简单。
源站请求，直接原路返回；正常配置下，mirror请求不影响源站请求及响应，源站nginx-server将流量复制到mirror站后，两者不再有任何交集。

2. 安装及配置

正常安装nginx 1.13.4及后续版本。下面配置在1.14.1中验证通过。

2.1 复制get及post请求

server {
        listen       80;
        server_name  web1.www.com;
        # 源站配置
        location / {
                access_log  /data/nginx/1.14.1/logs/web1/access.log  accesslog;
                mirror /mirror;
                mirror_request_body on;# Indicates whether the client request body is mirrored. default value is on.
                proxy_pass http://web1.upstream.name;
        }
        # 镜像站点配置
        location /mirror {
                internal; # 内部配置
                proxy_pass http://mirror.web1.upstream.name$request_uri;
                proxy_pass_request_body on; # Indicates whether the original request body is passed to the proxied server. default value is on
                proxy_set_header X-Original-URI $request_uri; # reset uri
        }
}

2.2 不允许复制post请求

默认是支持post复制的，需要通过配置来禁止

server {
        listen       80;
        server_name  web1.www.com;

        # 源站配置
        location / {
                access_log  /data/nginx/1.14.1/logs/web1/access.log  accesslog;
                mirror /mirror;
                mirror_request_body off;# Indicates whether the client request body is mirrored. default value is on.
                proxy_pass http://web1.upstream.name;
        }

        # 镜像站点配置
        location /mirror {
                # 判断请求方法，不是GET返回403
                if ($request_method != GET) {
                    return 403;
                }
                internal; # 内部配置
                proxy_pass http://mirror.web1.upstream.name$request_uri;
                proxy_pass_request_body off; # Indicates whether the original request body is passed to the proxied server. default value is on
                proxy_set_header Content-Length ""; # mirror_request_body/proxy_pass_request_body都设置为off，则Conten-length需要设置为""，否则有坑
                proxy_set_header X-Original-URI $request_uri; # 使用真实的url重置url
        }
}

3. 流量放大配置方法

配置多分mirror

server {
        listen       80;
        server_name  web1.www.com;
        # 源站配置
        location / {
                access_log  /data/nginx/1.14.1/logs/web1/access.log  accesslog;
                mirror /mirror;
                # 多加一份mirror，流量放大一倍
                mirror /mirror;
                mirror_request_body on;# Indicates whether the client request body is mirrored. default value is on.
                proxy_pass http://web1.upstream.name;
        }
        # 镜像站点配置
        location /mirror {
                internal; # 内部配置
                proxy_pass http://mirror.web1.upstream.name$request_uri;
                proxy_pass_request_body on; # Indicates whether the original request body is passed to the proxied server. default value is on
                proxy_set_header X-Original-URI $request_uri; # reset uri
        }
}

4. mirror日志

mirror中不支持配置access_log，解决方法：mirror-location跳转到server，在server中配置accesslog.

server {
        listen       80;
        server_name  web1.www.com;

        # 源站配置
        location / {
                access_log  /data/nginx/1.14.1/logs/web1/access.log  accesslog;
                mirror /mirror;
                mirror_request_body off;# Indicates whether the client request body is mirrored. default value is on.
                proxy_pass http://web1.upstream.name;
        }

        # 镜像站点配置
        location /mirror {
                internal; # 内部配置
                # 跳转到下面的内部server
                proxy_pass http://127.0.0.1:10901$request_uri;
                proxy_pass_request_body off; # Indicates whether the original request body is passed to the proxied server. default value is on
                # Content-Length必须配置在mirror中否则无效
                proxy_set_header Content-Length ""; # mirror_request_body/proxy_pass_request_body都设置为off，则Conten-length需要设置为""，否则有坑
                proxy_set_header X-Original-URI $request_uri; # 使用真实的url重置url
        }
}

server {
    # server没法设置为内部
    listen 127.0.0.1:10901;
    location / {
        # 判断放在server，使得post请求日志可以记录
        if ($request_method != GET) {
            return 403;
        }
        access_log /data/nginx/1.14.1/logs/web1/access.log  accesslog;
        proxy_pass http://mirror.web1.upstream.name;
    }
}

5. 性能评估

利用jemeter，在相同环境，使用30个并发，各请求3000次get或post方法，参数一样，一组为有mirror配置，另一组为没mirror配置，总体评估，mirror性能损失在5%以内，具体如下：

97. 坑

97.1 镜像配置不正确缺少相关日志

镜像配置不正确，导致复制操作没正常执行，此时nginx可能缺少错误日志，严重影响调试，所以非常建议配置镜像日志，配置方法如4. mirror日志。部分错误配置下错误信息在error日志中。

97.2 mirror_request_body/proxy_pass_request_body与Content-Length需配置一致

如果mirror_request_body或者proxy_pass_request_body设置为off，则Content-Length必须设置为""，因为nginx(mirror_request_body)或tomcat(mirror_request_body)处理post请求时，会根据Content-Length获取请求体，如果Content-Length不为空，而由于mirror_request_body或者proxy_pass_request_body设置为off，处理方以为post有内容，当request_body中没有，处理方会一直等待至超时，则前者为off，nginx会报upstream请求超时；后者为off，tomcat会报如下错误：

"2018-11-08T17:26:36.803+08:00" "331632b86ec64b829672066a96fc6324"      "department"        "group"   "project_name"        "hostname"    "127.0.0.1"     ""      "/post" "p=11"  "-"     "PostmanRuntime/7.1.1"  "ERROR" "xxx.GlobalControllerAdvice"       "operateExp"    "-"     "26"    "xxxx.GlobalControllerAdvice"       "unknown"       "org.springframework.http.converter.HttpMessageNotReadableException"    "I/O error while reading input message; nested exception is java.net.SocketTimeoutException"    "GlobalControllerAdvice中捕获全局异常"  "org.springframework.http.converter.HttpMessageNotReadableException: I/O error while reading input message; nested exception is java.net.SocketTimeoutException
        at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodArgumentResolver.readWithMessageConverters(AbstractMessageConverterMethodArgumentResolver.java:229)
        at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.readWithMessageConverters(RequestResponseBodyMethodProcessor.java:150)
        at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.resolveArgument(RequestResponseBodyMethodProcessor.java:128)
        at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:121)
        at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:158)
        at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:128)
        at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
        at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)