EFK (Elasticsearch + Fluentd + Kibana) 是kubernetes官方推荐的日志收集方案,我们一起了解一下fluentd是如何收集kubernetes集群日志的,庆祝一下fluentd从 CNCF 毕业。开始之前,希望你已经读过Docker 容器日志分析, 本文是其延生的第二篇。

注意 需要和ELK(Elasticsearch + Logstash + Kibana) 以及EFK(Elasticsearch + Filebeat + Kibana)区分,后一个EFK一般是原生部署。

CNCF , 全称Cloud Native Computing Foundation(云原生计算基金会),kubernetes也是其旗下,或者说大多数容器云项目都是其旗下。

部署EFK

k8s中部署efk,所用的yaml文件在 https://github.com/kubernetes/kubernetes/tree/master/cluster/addons/fluentd-elasticsearch ,你可以使用文章附录提供的脚本进行下载。

下载完成后执行 cd fluentd-elasticsearch && kubectl apply -f . 命令进行部署。

检查elasticsearch和kibana service:

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$ kubectl get svc -n kube-system
NAME                    TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)          AGE
elasticsearch-logging   NodePort    10.97.248.209    <none>        9200:32126/TCP   23d
kibana-logging          ClusterIP   10.103.126.183   <none>        5601/TCP         23d

检查fluentd DaemonSet:

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$ kubectl get ds -n kube-system
NAME                    DESIRED   CURRENT   READY   UP-TO-DATE   AVAILABLE   NODE SELECTOR                   AGE
fluentd-es-v2.4.0       2         2         2       2            2           <none>                          23d

这里我们知道了fluentd是以daemonset方式运行的,es和kibana是service方式。

注意 elasticsearch 默认部署文件是没有持久化的,如果需要持久化,需要调整其PVC设置。

fluentd 功能分析

  1. 查看fluentd的类型,没什么好说的

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    apiVersion: apps/v1
    kind: DaemonSet
    metadata:
      name: fluentd-es-v2.2.1
      namespace: kube-system
  2. 查看fluentd日志收集

    ``` containers:

    • name: fluentd-es image: k8s.gcr.io/fluentd-elasticsearch:v2.2.0

    volumeMounts: - name: varlog mountPath: /var/log - name: varlibdockercontainers mountPath: /var/lib/docker/containers readOnly: true - name: config-volume mountPath: /etc/fluent/config.d

    volumes: - name: varlog hostPath: path: /var/log - name: varlibdockercontainers hostPath: path: /var/lib/docker/containers - name: config-volume configMap: name: fluentd-es-config-v0.1.6 ```

    这里可以清晰的看到,fluentd以daemonset方式运作,然后把系统的 /var/lib/docker/containers 挂载,这个目录我们在Docker 容器日志分析中介绍过,这是docker容器日志存放路径, 这样fluentd就完成了对容器默认日志的读取。

    fluentd的配置文件是以configmap形式加载,继续往下看看。

  3. 收集容器日志配置

    收集容器日志主要在 containers.input.conf,如下:

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    <source>
      @id fluentd-containers.log
      @type tail
      path /var/log/containers/*.log
      pos_file /var/log/es-containers.log.pos
      tag raw.kubernetes.*
      read_from_head true
      <parse>
        @type multi_format
        <pattern>
          format json
          time_key time
          time_format %Y-%m-%dT%H:%M:%S.%NZ
        </pattern>
        <pattern>
          format /^(?<time>.+) (?<stream>stdout|stderr) [^ ]* (?<log>.*)$/
          time_format %Y-%m-%dT%H:%M:%S.%N%:z
        </pattern>
      </parse>
    </source>

    细心的你会发现挂载的容器目录是 /var/lib/docker/containers ,日志应该都在这里,但是配置的监听的目录却是 /var/log/containers 。官方贴心的给出了注释,主要内容如下:

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     # Example
        # =======
        # ...
        #
        # The Kubernetes fluentd plugin is used to write the Kubernetes metadata to the log
        # record & add labels to the log record if properly configured. This enables users
        # to filter & search logs on any metadata.
        # For example a Docker container's logs might be in the directory:
        #
        #  /var/lib/docker/containers/997599971ee6366d4a5920d25b79286ad45ff37a74494f262e3bc98d909d0a7b
        #
        # and in the file:
        #
        #  997599971ee6366d4a5920d25b79286ad45ff37a74494f262e3bc98d909d0a7b-json.log
        #
        # where 997599971ee6... is the Docker ID of the running container.
        # The Kubernetes kubelet makes a symbolic link to this file on the host machine
        # in the /var/log/containers directory which includes the pod name and the Kubernetes
        # container name:
        #
        #    synthetic-logger-0.25lps-pod_default_synth-lgr-997599971ee6366d4a5920d25b79286ad45ff37a74494f262e3bc98d909d0a7b.log
        #    ->
        #    /var/lib/docker/containers/997599971ee6366d4a5920d25b79286ad45ff37a74494f262e3bc98d909d0a7b/997599971ee6366d4a5920d25b79286ad45ff37a74494f262e3bc98d909d0a7b-json.log
        #
        # The /var/log directory on the host is mapped to the /var/log directory in the container
        # running this instance of Fluentd and we end up collecting the file:
        #
        #   /var/log/containers/synthetic-logger-0.25lps-pod_default_synth-lgr-997599971ee6366d4a5920d25b79286ad45ff37a74494f262e3bc98d909d0a7b.log
        #
  4. 日志上传到elasticsearch

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    output.conf: |-
        <match **>
          @id elasticsearch
          @type elasticsearch
          @log_level info
          type_name _doc
          include_tag_key true
          host elasticsearch-logging
          port 9200
          logstash_format true
          <buffer>
            @type file
            path /var/log/fluentd-buffers/kubernetes.system.buffer
            flush_mode interval
            retry_type exponential_backoff
            flush_thread_count 2
            flush_interval 5s
            retry_forever
            retry_max_interval 30
            chunk_limit_size 2M
            queue_limit_length 8
            overflow_action block
          </buffer>
        </match>

    这里注意一下其中的hostport,均是elasticsearch service中定义的,如果修改过需要保持一致。fluentd也支持日志数据上传到外部的elasticsearch,也就是前文的elk/efk原生。

附录

  1. 架构图

logging-with-node-agent

  1. 下载脚本文件 download.sh

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    for file in es-service es-statefulset fluentd-es-configmap fluentd-es-ds kibana-deployment kibana-service; do curl -o $file.yaml https://raw.githubusercontent.com/kubernetes/kubernetes/master/cluster/addons/fluentd-elasticsearch/$file.yaml; done
  2. 参考链接: