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Docker 中的 .NET 异常了怎么抓 Dump 每日动态

日期：2023-06-26 12:32:50 来源：博客园

一：背景1. 讲故事

有很多朋友跟我说，在 Windows 上看过你文章知道了怎么抓 Crash, CPU爆高，内存暴涨等各种Dump，为什么你没有写在 Docker 中如何抓的相关文章呢？瞧不上吗？

哈哈，在DUMP的分析旅程中，跑在 Docker 中的 .NET 占比真的不多，大概10个dump有 1-2 个是 docker 中的，市场决定了我的研究方向，为了弥补这一块的空洞，决定写一篇文章来分享下这三大异常下的捕获吧。

二：Docker 下的三大异常捕获1. crash dump 捕获

前不久我写了一篇 Linux 上的 .NET 崩溃了怎么抓 Dump （https://www.cnblogs.com/huangxincheng/p/17440153.html）的文章，使用了微软推荐的环境变量方式，其实这在 Docker 中是一样适用的。

(资料图片)

为了让 webapi崩溃退出，我故意造一个栈溢出异常，参考代码如下：

public class Program    {        public static void Main(string[] args)        {            var builder = WebApplication.CreateBuilder(args);            builder.Services.AddAuthorization();            var app = builder.Build();            app.UseAuthorization();            //1. crash            Task.Factory.StartNew(() =>            {                Test("a");            });            app.Run();        }        public static string Test(string a)        {            return Test("a" + a.Length);        }    }

有了代码之后，接下来写一个 Dockerfile，主要就是把三个环境变量塞进去。

FROM mcr.microsoft.com/dotnet/aspnet:6.0 AS runtimeWORKDIR /appCOPY ./ ./# 1. 使用中科大镜像源RUN sed -i "s/deb.debian.org/mirrors.ustc.edu.cn/g" /etc/apt/sources.listENV COMPlus_DbgMiniDumpType 4ENV COMPlus_DbgMiniDumpName /dumps/%p-%e-%h-%t.dmpENV COMPlus_DbgEnableMiniDump 1ENTRYPOINT ["dotnet", "AspNetWebApi.dll"]

这里有一个细节，为了能够让 Docker 中的 webapi 能够访问到，将 localhost 设置为 * ，修改 appsettings.json如下：

{  "urls": "http://*:5001",  "Logging": {    "LogLevel": {      "Default": "Information",      "Microsoft.AspNetCore": "Warning"    }  },  "AllowedHosts": "*"}

有了这些基础最后就是 docker build & docker run 啦。

[root@localhost data]# docker build -t aspnetapp .[+] Building 0.3s (9/9) FINISHED                                                                          => [internal] load build definition from Dockerfile                                                0.0s => => transferring dockerfile: 447B                                                                0.0s => [internal] load .dockerignore                                                                   0.0s => => transferring context: 2B                                                                     0.0s => [internal] load metadata for mcr.microsoft.com/dotnet/aspnet:6.0                                0.3s => [1/4] FROM mcr.microsoft.com/dotnet/aspnet:6.0@sha256:a2a04325fdb2a871e964c89318921f82f6435b54  0.0s => [internal] load build context                                                                   0.0s => => transferring context: 860B                                                                   0.0s => CACHED [2/4] WORKDIR /app                                                                       0.0s => CACHED [3/4] COPY ./ ./                                                                         0.0s => CACHED [4/4] RUN sed -i "s/deb.debian.org/mirrors.ustc.edu.cn/g" /etc/apt/sources.list          0.0s => exporting to image                                                                              0.0s => => exporting layers                                                                             0.0s => => writing image sha256:be69203995c0e5423b2af913549e618d7ee8306fff3961118ff403b1359ae571        0.0s => => naming to docker.io/library/aspnetapp                                                        0.0s[root@localhost data]# docker run -itd  -p 5001:5001 --privileged -v /data2:/dumps --name aspnetcore_sample aspnetappca34c9274d998096f8562cbef3a43a7cbd9aa5ff2923e0f3e702b159e0b2f447[root@localhost data]# docker ps -aCONTAINER ID   IMAGE       COMMAND                  CREATED          STATUS                       PORTS     NAMESca34c9274d99   aspnetapp   "dotnet AspNetWebApi…"   20 seconds ago   Exited (139) 9 seconds ago             aspnetcore_sample[root@localhost data]# docker logs ca34c9274d99   ...   at AspNetWebApi.Program.Test(System.String)   at AspNetWebApi.Program.Test(System.String)   at AspNetWebApi.Program.Test(System.String)   at AspNetWebApi.Program.Test(System.String)   at AspNetWebApi.Program+<>c.b__0_0()   at System.Threading.Tasks.Task.InnerInvoke()   at System.Threading.Tasks.Task+<>c.<.cctor>b__272_0(System.Object)   at System.Threading.ExecutionContext.RunFromThreadPoolDispatchLoop(System.Threading.Thread, System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object)   at System.Threading.Tasks.Task.ExecuteWithThreadLocal(System.Threading.Tasks.Task ByRef, System.Threading.Thread)   at System.Threading.Tasks.Task.ExecuteEntryUnsafe(System.Threading.Thread)   at System.Threading.ThreadPoolWorkQueue.Dispatch()   at System.Threading.PortableThreadPool+WorkerThread.WorkerThreadStart()   at System.Threading.Thread.StartCallback()[createdump] Gathering state for process 1 dotnet[createdump] Crashing thread 0017 signal 6 (0006)[createdump] Writing full dump to file /dumps/1-dotnet-ca34c9274d99-1687746929.dmp[createdump] Written 261320704 bytes (63799 pages) to core file[createdump] Target process is alive[createdump] Dump successfully written[root@localhost data2]# cd /data2[root@localhost data2]# ls -lntotal 255288-rw-------. 1 0 0 261414912 Jun 26 10:35 1-dotnet-ca34c9274d99-1687746929.dmp

上面的脚本已经写的非常清楚了，这里有几个注意点提一下：

--privileged

一定要加上特殊权限，否则生成 dump 的时候会提示无权限。

-v /data2:/dumps

防止dump丢失，记得挂载到宿主机目录或者共享容器中。

2. 内存暴涨 dump 捕获

要想对 docker 中的 .NET 程序内存进行监控，我一直都是极力推荐 procdump，目前最新的是版本是 1.5， github官网地址： https://github.com/Sysinternals/ProcDump-for-Linux 鉴于现在访问 github 太慢，大家可以把 procdump_1.5-16239_amd64.deb下载到本地，为什么下载它，是因为容器中是 debain 系统。

下载好了之后放到项目中，使用默认代码骨架：

public class Program    {        public static void Main(string[] args)        {            var builder = WebApplication.CreateBuilder(args);            builder.Services.AddAuthorization();            var app = builder.Build();            app.UseAuthorization();            app.Run();        }    }

接下来就是写 dockerfile 了，这里有一个细节，就是如何在 Docker 中开启多进程，这里用 start.sh 脚本的方式开启，参考代码如下：

FROM mcr.microsoft.com/dotnet/aspnet:6.0 AS runtimeWORKDIR /appCOPY ./ ./# 1. 使用中科大镜像源RUN sed -i "s/deb.debian.org/mirrors.ustc.edu.cn/g" /etc/apt/sources.list# 2. 安装 gdb & procdumpRUN apt-get update && apt-get install -y gdbRUN dpkg -i procdump.debRUN echo "#!/bin/bash \n\procdump -m 30 -w dotnet /dumps & \n\dotnet \$1 \n\" > ./start.shRUN chmod +x ./start.shENTRYPOINT ["./start.sh", "AspNetWebApi.dll"]

有了这些设置后，接下来就是 publish 代码用 docker 构建啦，为了方便演示，这里就用 前台模式开启了哈。

[root@localhost data]# docker build -t aspnetapp .[+] Building 11.5s (13/13) FINISHED              [root@localhost data]# docker rm -f aspnetcore_sampleaspnetcore_sample[root@localhost data]# docker run -it --rm  -p 5001:5001 --privileged -v /data2:/dumps --name aspnetcore_sample aspnetappProcDump v1.5 - Sysinternals process dump utilityCopyright (C) 2023 Microsoft Corporation. All rights reserved. Licensed under the MIT license.Mark Russinovich, Mario Hewardt, John Salem, Javid HabibiSysinternals - www.sysinternals.comMonitors one or more processes and writes a core dump file when the processes exceeds thespecified criteria.[02:57:34 - INFO]: Waiting for processes "dotnet" to launch[02:57:34 - INFO]: Press Ctrl-C to end monitoring without terminating the process(es).Process Name:                           dotnetCPU Threshold:                          n/aCommit Threshold:                       >=30 MBThread Threshold:                       n/aFile Descriptor Threshold:              n/aSignal:                                 n/aException monitor                       OffPolling Interval (ms):                  1000Threshold (s):                          10Number of Dumps:                        1Output directory:                       /dumps[02:57:34 - INFO]: Starting monitor for process dotnet (9)info: Microsoft.Hosting.Lifetime[14]      Now listening on: http://[::]:5001info: Microsoft.Hosting.Lifetime[0]      Application started. Press Ctrl+C to shut down.info: Microsoft.Hosting.Lifetime[0]      Hosting environment: Productioninfo: Microsoft.Hosting.Lifetime[0]      Content root path: /app/[02:57:35 - INFO]: Trigger: Commit usage:48MB on process ID: 9[createdump] Gathering state for process 9 dotnet[createdump] Writing full dump to file /dumps/dotnet_commit_2023-06-26_02:57:35.9[createdump] Written 254459904 bytes (62124 pages) to core file[createdump] Target process is alive[createdump] Dump successfully written[02:57:35 - INFO]: Core dump 0 generated: /dumps/dotnet_commit_2023-06-26_02:57:35.9[02:57:36 - INFO]: Stopping monitors for process: dotnet (9)[root@localhost data2]# ls -lhtotal 243M-rw-------. 1 root root 243M Jun 26 10:57 dotnet_commit_2023-06-26_02:57:35.9

从脚本信息看，当内存到了 48MB的时候触发的 dump 生成，也成功的进入了 /dumps目录中，太棒了。

3. cpu爆高 dump 捕获

抓 cpu 爆高的dump最好的方式就是多抓几个，比如说：当 CPU >20% 连续超过 5s 抓 2个dump，这种方式抓的dump很容易就能找到真凶，为了方便演示，让两个 cpu 直接打满，参考代码如下：

public static void Main(string[] args)        {            var builder = WebApplication.CreateBuilder(args);            builder.Services.AddAuthorization();            var app = builder.Build();            app.UseAuthorization();            //3. cpu            app.MapGet("/cpu", (HttpContext httpContext) =>            {                Task.Factory.StartNew(() => { bool b = true; while (true) { b = !b; } });                Task.Factory.StartNew(() => { bool b = true; while (true) { b = !b; } });                return new WeatherForecast();            });            app.Run();        }

接下来就是修改 dockerfile，因为我的虚拟机是 8 核心，如果两个核心被打满，那应该会占用大概 24% 的 cpu 利用率，所以脚本中就设置 20% 吧。

FROM mcr.microsoft.com/dotnet/aspnet:6.0 AS runtimeWORKDIR /appCOPY ./ ./# 1. 使用中科大镜像源RUN sed -i "s/deb.debian.org/mirrors.ustc.edu.cn/g" /etc/apt/sources.list# 2. 安装 wgetRUN apt-get update && apt-get install -y gdbRUN dpkg -i procdump.debRUN echo "#!/bin/bash \n\procdump -c 20 -n 2 -s 5 -w dotnet /dumps & \n\dotnet \$1 \n\" > ./start.shRUN chmod +x ./start.shENTRYPOINT ["./start.sh", "AspNetWebApi.dll"]

最后就是 docker 构建。

[root@localhost data]# docker build -t aspnetapp .[+] Building 0.4s (13/13) FINISHED[root@localhost data]# docker run -it --rm  -p 5001:5001 --privileged -v /data2:/dumps --name aspnetcore_sample aspnetappProcDump v1.5 - Sysinternals process dump utilityCopyright (C) 2023 Microsoft Corporation. All rights reserved. Licensed under the MIT license.Mark Russinovich, Mario Hewardt, John Salem, Javid HabibiSysinternals - www.sysinternals.comMonitors one or more processes and writes a core dump file when the processes exceeds thespecified criteria.[03:35:56 - INFO]: Waiting for processes "dotnet" to launch[03:35:56 - INFO]: Press Ctrl-C to end monitoring without terminating the process(es).Process Name:                           dotnetCPU Threshold:                          >= 20%Commit Threshold:                       n/aThread Threshold:                       n/aFile Descriptor Threshold:              n/aSignal:                                 n/aException monitor                       OffPolling Interval (ms):                  1000Threshold (s):                          5Number of Dumps:                        2Output directory:                       /dumps[03:35:56 - INFO]: Starting monitor for process dotnet (8)info: Microsoft.Hosting.Lifetime[14]      Now listening on: http://[::]:5001info: Microsoft.Hosting.Lifetime[0]      Application started. Press Ctrl+C to shut down.info: Microsoft.Hosting.Lifetime[0]      Hosting environment: Productioninfo: Microsoft.Hosting.Lifetime[0]      Content root path: /app/

看输出是正在监控，接下来我们访问下网址： http://192.168.17.129:5001/cpu，稍等片刻之后就会生成两个dump 文件。

三：总结

虽然Docker中的 .NET 程序占比较少，但把经验总结出来还是很值得的，以后有人问怎么抓，可以把这篇文章直接丢过去啦！

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