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.NET Core + K8S + Loki 玩转日志聚合

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2020-07-28 16:38

Grafana loki

1. Intro

最近在了解日志聚合系统，正好前几天看到一篇文章《用了日志系统新贵Loki，ELK突然不香了！》，所以就决定动手体验一下。本文就带大家快速了解下Loki，并简单介绍.NET Core如何集成Loki。

2. What's Loki Stack

Grafana Loki like Prometheus, but for logs。其是一个水平可扩展，高可用性，多租户的日志聚合系统，基于Apatch 2.0开源。其有三部分组成：

  1. Loki 是主服务器，负责存储日志和处理查询。对标ELK中的ElasticSearch。
  2. Promtail 是代理，负责收集日志并将其发送给loki。对标ELK中的Logstash。
  3. Grafana提供用户界面。对标ELK中的Kibana。

3. Why Use Loki

日志聚合系统的目的是为了方便我们进行日志跟踪和故障排查，尤其在云原生的环境之下。目前主流的日志聚合系统，当数ELK、EFK和Loki。Loki相较于ELK Stack有以下优势：

  • Elasticsearch中的数据作为非结构化JSON对象存储在磁盘上，Loki以二进制的形式存储。

  • Elasticsearch采用全文索引，倒排索引的切分和共享的成本较高。Loki仅索引元数据，比如标签。

  • 和Prometheus无缝集成。

4. How Use Loki

首先我们先来基于Heml安装Loki到本地K8S集群。

1. 添加Loki Chart 仓库：

PS C:\Users\Shengjie> helm repo add loki https://grafana.github.io/loki/charts"loki" has been added to your repositoriesPS C:\Users\Shengjie> helm repo updateHang tight while we grab the latest from your chart repositories......Successfully got an update from the "stable" chart repository...Successfully got an update from the "loki" chart repositoryUpdate Complete. ⎈ Happy Helming!⎈

2. 安装Loki Stack

PS C:\Users\Shengjie> helm search hub loki-stackURL                                             CHART VERSION   APP VERSION     DESCRIPTIONhttps://hub.helm.sh/charts/loki/loki-stack      0.38.3          v1.5.0          Loki: like Prometheus, but for logs.PS C:\Users\Shengjie> helm show values loki/loki-stackloki:  enabled: true
promtail:  enabled: true
fluent-bit:  enabled: false
grafana:  enabled: false  sidecar:    datasources:      enabled: true  image:    tag: 6.7.0
prometheus:  enabled: false
filebeat:  enabled: false  filebeatConfig:    filebeat.yml: |      # logging.level: debug      filebeat.inputs:      - type: container        paths:          - /var/log/containers/*.log        processors:        - add_kubernetes_metadata:            host: ${NODE_NAME}            matchers:            - logs_path:                logs_path: "/var/log/containers/"      output.logstash:        hosts: ["logstash-loki:5044"]
logstash:  enabled: false  image:    repository: grafana/logstash-output-loki    tag: 1.0.1  filters:    main: |-      filter {        if [kubernetes] {          mutate {            add_field => {              "container_name" => "%{[kubernetes][container][name]}"              "namespace" => "%{[kubernetes][namespace]}"              "pod" => "%{[kubernetes][pod][name]}"            }            replace => { "host" => "%{[kubernetes][node][name]}"}          }        }        mutate {          remove_field => ["tags"]        }      }  outputs:    main: |-      output {        loki {          url => "http://loki:3100/loki/api/v1/push"          #username => "test"          #password => "test"        }        # stdout { codec => rubydebug }      }

从上面的Values中，可以看出，可以自定义启用fluent-bit、grafana、filebeat、prometheus、logstash组件。这里我们仅启用grafana日志界面。

PS C:\Users\Shengjie> helm install loki-stack loki/loki-stack --set grafana.enabled=truecoalesce.go:165: warning: skipped value for filters: Not a table.coalesce.go:165: warning: skipped value for filters: Not a table.NAME: loki-stackLAST DEPLOYED: Sun Jul 26 11:58:11 2020NAMESPACE: defaultSTATUS: deployedREVISION: 1NOTES:The Loki stack has been deployed to your cluster. Loki can now be added as a datasource in Grafana.
See http://docs.grafana.org/features/datasources/loki/ for more detail.

3. 登录Grafana

首先确认Loki是否成功部署：

PS C:\Users\Shengjie> helm listNAME            NAMESPACE       REVISION        UPDATED                                 STATUS          CHART                   APP VERSIONloki-stack      default         1               2020-07-26 11:58:11.022896 +0800 CST    deployed        loki-stack-0.38.3       v1.5.0PS C:\Users\Shengjie> kubectl get pod -wNAME                                READY   STATUS        RESTARTS   AGEloki-stack-0                        1/1     Running       0          2m33sloki-stack-grafana-c447cfbd-z6tbg   1/1     Running       0          2m33sloki-stack-promtail-j47hl           1/1     Running       0          2m33sPS C:\Users\Shengjie> kubectl get svc -wNAME                  TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGEkubernetes            ClusterIP   10.96.0.1               443/TCP    56dloki-stack            ClusterIP   10.110.83.209           3100/TCP   2m52sloki-stack-grafana    ClusterIP   10.111.24.26            80/TCP     2m52sloki-stack-headless   ClusterIP   None                    3100/TCP   2m52s

从上面可知，已经成功启动，其中loki暴露的容器端口为3100，grafana暴露的端口为80。因此我们下一步需要进行端口转发，才能访问grafana。

PS C:\Users\Shengjie> kubectl port-forward svc/loki-stack-grafana 3000:80Forwarding from 127.0.0.1:3000 -> 3000Forwarding from [::1]:3000 -> 3000

然后本地浏览器打开http://localhost:3000/就可以访问了。其默认用户是admin，默认密码在哪里呢，别慌，我们去看下loki-stack chart 的readme：

PS C:\Users\Shengjie> helm show readme loki/loki-stack# Loki-Stack Helm Chart## Prerequisites
Make sure you have Helm [installed](https://helm.sh/docs/using_helm/#installing-helm) and[deployed](https://helm.sh/docs/using_helm/#installing-tiller) to your cluster. Then addLoki's chart repository to Helm:$ helm repo add loki https://grafana.github.io/loki/charts
You can update the chart repository by running:$ helm repo update
## Deploy Loki and Promtail to your cluster### Deploy with default config$ helm upgrade --install loki loki/loki-stack### Deploy in a custom namespace$ helm upgrade --install loki --namespace=loki-stack loki/loki-stack
### Deploy with custom config
$ helm upgrade --install loki loki/loki-stack --set "key1=val1,key2=val2,..."## Deploy Loki and Fluent Bit to your cluster$ helm upgrade --install loki loki/loki-stack \    --set fluent-bit.enabled=true,promtail.enabled=false## Deploy Grafana to your clusterThe chart loki-stack contains a pre-configured Grafana, simply use `--set grafana.enabled=true`
To get the admin password for the Grafana pod, run the following command:$ kubectl get secret --namespace  loki-grafana -o jsonpath="{.data.admin-password}" | base64 --decode ; echoTo access the Grafana UI, run the following command:$ kubectl port-forward --namespace  service/loki-grafana 3000:80Navigate to http://localhost:3000 and login with `admin` and the password output above.Then follow the [instructions for adding the loki datasource](/docs/getting-started/grafana.md), using the URL `http://loki:3100/`

上面已经说了很清楚了，可以从secret中获取。

如果在windows powersheel中执行，需要分两步：1. 先获取base64加密的密码PS C:\Users\Shengjie> $pwd= kubectl get secret --namespace default loki-stack-grafana -o jsonpath="{.data.admin-password}"2. decode base64PS C:\Users\Shengjie> [Text.Encoding]::Utf8.GetString([Convert]::FromBase64String($pwd))CjnbkkQmwQynZ96gCsynSf0elYQLOp4dyuDnp9jJ
------------------------Linux命令行执行：shengjie@Thinkpad:/mnt/c/Users/Shengjie$ kubectl get secret --namespace default loki-stack-grafana -o jsonpath="{.data.admin-password}" | base64 --decode ; echoCjnbkkQmwQynZ96gCsynSf0elYQLOp4dyuDnp9jJ

然后使用admin/CjnbkkQmwQynZ96gCsynSf0elYQLOp4dyuDnp9jJ即可成功登录http://localhost:3000/。

Grafnan Explore

5. Use Loki With .NET Core

下一步，我们就来创建一个ASP.NET Core Web 应用，将日志记录到Loki，并通过Grafana进行聚合分析。

PS C:\Users\Shengjie> dotnet new web -n Loki.K8s.DemoThe template "ASP.NET Core Empty" was created successfully.
Processing post-creation actions...Running 'dotnet restore' on Loki.K8s.Demo\Loki.K8s.Demo.csproj...  Determining projects to restore...  Restored C:\Users\Shengjie\Loki.K8s.Demo\Loki.K8s.Demo.csproj (in 150 ms).
Restore succeeded.PS C:\Users\Shengjie> cd .\Loki.K8s.Demo\# 添加Serilog.AspNetCore和Serilog.Sinks.Loki Nuget包。PS C:\Users\Shengjie\Loki.K8s.Demo> dotnet add package Serilog.AspNetCorePS C:\Users\Shengjie\Loki.K8s.Demo> dotnet add package Serilog.Sinks.Loki

从上可知，日志组件选用的是Serilog，因为其支持持久化日志到Loki。修改Program.cs如下：

public static IHostBuilder CreateHostBuilder(string[] args) =>    Host.CreateDefaultBuilder(args)        .ConfigureWebHostDefaults(webBuilder =>        {            webBuilder.UseStartup();        }).UseSerilog((ctx, cfg) =>        {            //cfg.MinimumLevel.Override("Microsoft", LogEventLevel.Warning);//Microsoft框架本身的日志，仅输出Warning以上级别            cfg.Enrich.FromLogContext()            .Enrich.WithProperty("App", ctx.HostingEnvironment.ApplicationName)            .Enrich.WithProperty("ENV", ctx.HostingEnvironment.EnvironmentName)            .WriteTo.LokiHttp(new NoAuthCredentials("http://localhost:3100"))//配置Loki Url和认证方式            .WriteTo.Console();        });

修改Startup.cs的Configure方法如下：

public void Configure(IApplicationBuilder app, IWebHostEnvironment env,ILogger logger){    if (env.IsDevelopment())    {        app.UseDeveloperExceptionPage();    }    app.UseRouting();    app.UseEndpoints(endpoints =>    {        endpoints.MapGet("/", async context =>        {            logger.LogInformation("start handle request!");            await context.Response.WriteAsync("Hello World!");            logger.LogInformation("end handle request!");        });    });}

因为不想把应用打包成镜像运行到K8S中，所以我们需要把K8S的Loki服务做一次端口转发暴露到本机，转发后，就可以使用http://localhost:3100作为Loki的Url进行日志写入啦。

PS C:\Users\Shengjie\Loki.K8s.Demo> kubectl port-forward svc/loki-stack 3100:3100Forwarding from 127.0.0.1:3100 -> 3100Forwarding from [::1]:3100 -> 3100

运行项目后，重新打开Grafana，添加过滤条件，就可以查看应用日志了。

参考资料：

  1. 日志聚合工具loki
  2. CSDN-linkt1234-Loki
  3. Loki官方文档


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