Kubernetes 集群本身不提供日志收集的解决方案，一般来说有主要的3种方案来做日志收集：
1、在每个节点上运行一个 agent 来收集日志
由于这种 agent 必须在每个节点上运行，所以直接使用 DaemonSet 控制器运行该应用程序即可
这种方法也仅仅适用于收集输出到 stdout 和 stderr 的应用程序日志
简单来说，本方式就是在每个node上各运行一个日志代理容器，
对本节点/var/log和 /var/lib/docker/containers/两个目录下的日志进行采集
2、在每个 Pod 中包含一个 sidecar 容器来收集应用日志
在 sidecar 容器中运行日志采集代理程序会导致大量资源消耗，因为你有多少个要采集的 Pod，就需要运行多少个采集代理程序，另外还无法使用 kubectl logs 命令来访问这些日志
3、直接在应用程序中将日志信息推送到采集后端

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Kubernetes 中比较流行的日志收集解决方案是 Elasticsearch、Fluentd 和 Kibana（EFK）技术栈，也是官方现在比较推荐的一种方案
Elasticsearch 是一个实时的、分布式的可扩展的搜索引擎，允许进行全文、结构化搜索，它通常用于索引和搜索大量日志数据，也可用于搜索许多不同类型的文档

创建 Elasticsearch 集群
一般使用3个 Elasticsearch Pod 来避免高可用下多节点集群中出现的“脑裂”问题，并且使用StatefulSet控制器来创建Elasticsearch Pod
创建StatefulSet pod时，直接在其pvc模板中使用StorageClass自动生成pv和pvc，可以实现数据持久化，nfs-client-provisioner已经提前准备好了。
1、创建独立的命名空间

apiVersion: v1
kind: Namespace
metadata:
  name: logging

2、创建StorageClas，也可以使用已经存在的StorageClas

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: es-data-db
provisioner: fuseim.pri/ifs      # 该值需要和 provisioner 配置的保持一致

3、创建StatefulSet pod前需要先创建无头服务

kind: Service
apiVersion: v1
metadata:
  name: elasticsearch
  namespace: logging
  labels:
    app: elasticsearch
spec:
  selector:
    app: elasticsearch
  clusterIP: None
  ports:
    - port: 9200
      name: rest
    - port: 9300
      name: inter-node

4、创建elasticsearch statefulset pod
$ docker pull docker.elastic.co/elasticsearch/elasticsearch-oss:6.4.3
$ docker pull busybox

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: es-cluster
  namespace: logging
spec:
  serviceName: elasticsearch
  replicas: 3
  selector:
    matchLabels:
      app: elasticsearch
  template:
    metadata:
      labels:
        app: elasticsearch
    spec:
      containers:
      - name: elasticsearch
        image: docker.io/elasticsearch:latest
        resources:
            limits:
              cpu: 1000m
            requests:
              cpu: 100m
        ports:
        - containerPort: 9200
          name: rest
          protocol: TCP
        - containerPort: 9300
          name: inter-node
          protocol: TCP
        volumeMounts:
        - name: data
          mountPath: /usr/share/elasticsearch/data
        env:
          - name: cluster.name
            value: k8s-logs
          - name: node.name
            valueFrom:
              fieldRef:
                fieldPath: metadata.name
          - name: discovery.zen.ping.unicast.hosts
            value: "es-cluster-0.elasticsearch,es-cluster-1.elasticsearch,es-cluster-2.elasticsearch"
          - name: discovery.zen.minimum_master_nodes
            value: "2"
          - name: ES_JAVA_OPTS
            value: "-Xms512m -Xmx512m"
      initContainers:
      - name: fix-permissions
        image: busybox
        command: ["sh", "-c", "chown -R 1000:1000 /usr/share/elasticsearch/data"]
        securityContext:
          privileged: true
        volumeMounts:
        - name: data
          mountPath: /usr/share/elasticsearch/data
      - name: increase-vm-max-map
        image: busybox
        command: ["sysctl", "-w", "vm.max_map_count=262144"]
        securityContext:
          privileged: true
      - name: increase-fd-ulimit
        image: busybox
        command: ["sh", "-c", "ulimit -n 65536"]
        securityContext:
          privileged: true
  volumeClaimTemplates:
  - metadata:
      name: data
      labels:
        app: elasticsearch
    spec:
      accessModes: [ "ReadWriteOnce" ]
      storageClassName: es-data-db
      resources:
        requests:
          storage: 100Gi

$ kubectl get pod -n logging
NAME READY STATUS RESTARTS AGE
es-cluster-0 1/1 Running 0 42s
es-cluster-1 1/1 Running 0 10m
es-cluster-2 1/1 Running 0 9m49s
在nfs服务器上会自动生成3个目录，用于这3个pod存储数据
$ cd /data/k8s
$ ls
logging-data-es-cluster-0-pvc-98c87fc5-c581-11e9-964d-000c29d8512b/
logging-data-es-cluster-1-pvc-07872570-c590-11e9-964d-000c29d8512b/
logging-data-es-cluster-2-pvc-27e15977-c590-11e9-964d-000c29d8512b/
检查es集群状态
$ kubectl port-forward es-cluster-0 9200:9200 --namespace=logging
在另外一个窗口执行
$ curl http://localhost:9200/_cluster/state?pretty

用deployment控制器创建kibana

apiVersion: v1
kind: Service
metadata:
  name: kibana
  namespace: logging
  labels:
    app: kibana
spec:
  ports:
  - port: 5601
  type: NodePort
  selector:
    app: kibana

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: kibana
  namespace: logging
  labels:
    app: kibana
spec:
  selector:
    matchLabels:
      app: kibana
  template:
    metadata:
      labels:
        app: kibana
    spec:
      containers:
      - name: kibana
        image: docker.elastic.co/kibana/kibana-oss:6.4.3
        resources:
          limits:
            cpu: 1000m
          requests:
            cpu: 100m
        env:
          - name: ELASTICSEARCH_URL
            value: http://elasticsearch:9200
        ports:
        - containerPort: 5601

$ kubectl get svc -n logging |grep kibana
kibana NodePort 10.111.239.0 5601:32081/TCP 114m
访问kibana
http://192.168.1.243:32081

安装配置 Fluentd
1、通过 ConfigMap 对象来指定 Fluentd 配置文件

kind: ConfigMap
apiVersion: v1
metadata:
  name: fluentd-config
  namespace: logging
  labels:
    addonmanager.kubernetes.io/mode: Reconcile
data:
  system.conf: |-
    
      root_dir /tmp/fluentd-buffers/
    
  containers.input.conf: |-
    
      @id fluentd-containers.log
      @type tail
      path /var/log/containers/*.log
      pos_file /var/log/es-containers.log.pos
      time_format %Y-%m-%dT%H:%M:%S.%NZ
      localtime
      tag raw.kubernetes.*
      format json
      read_from_head true
    
    
      @id raw.kubernetes
      @type detect_exceptions
      remove_tag_prefix raw
      message log
      stream stream
      multiline_flush_interval 5
      max_bytes 500000
      max_lines 1000
    
  system.input.conf: |-
    
      @id journald-docker
      @type systemd
      filters [{ "_SYSTEMD_UNIT": "docker.service" }]
      
        @type local
        persistent true
      
      read_from_head true
      tag docker
    
    
      @id journald-kubelet
      @type systemd
      filters [{ "_SYSTEMD_UNIT": "kubelet.service" }]
      
        @type local
        persistent true
      
      read_from_head true
      tag kubelet
    
  forward.input.conf: |-
    
      @type forward
    
  output.conf: |-
    
      @type kubernetes_metadata
    
    
      @id elasticsearch
      @type elasticsearch
      @log_level info
      include_tag_key true
      host elasticsearch
      port 9200
      logstash_format true
      request_timeout    30s
      
        @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
      
    

上面配置文件中我们配置了 docker 容器日志目录以及 docker、kubelet 应用的日志的收集，收集到数据经过处理后发送到 elasticsearch:9200 服务
2、使用DaemonSet创建fluentd pod
$ docker pull cnych/fluentd-elasticsearch:v2.0.4
$ docker info
Docker Root Dir: /var/lib/docker

apiVersion: v1
kind: ServiceAccount
metadata:
  name: fluentd-es
  namespace: logging
  labels:
    k8s-app: fluentd-es
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: fluentd-es
  labels:
    k8s-app: fluentd-es
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
rules:
- apiGroups:
  - ""
  resources:
  - "namespaces"
  - "pods"
  verbs:
  - "get"
  - "watch"
  - "list"
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: fluentd-es
  labels:
    k8s-app: fluentd-es
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
subjects:
- kind: ServiceAccount
  name: fluentd-es
  namespace: logging
  apiGroup: ""
roleRef:
  kind: ClusterRole
  name: fluentd-es
  apiGroup: ""
---
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: fluentd-es
  namespace: logging
  labels:
    k8s-app: fluentd-es
    version: v2.0.4
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
spec:
  selector:
    matchLabels:
      k8s-app: fluentd-es
      version: v2.0.4
  template:
    metadata:
      labels:
        k8s-app: fluentd-es
        kubernetes.io/cluster-service: "true"
        version: v2.0.4
      annotations:
        scheduler.alpha.kubernetes.io/critical-pod: ''
    spec:
      serviceAccountName: fluentd-es
      containers:
      - name: fluentd-es
        image: cnych/fluentd-elasticsearch:v2.0.4
        env:
        - name: FLUENTD_ARGS
          value: --no-supervisor -q
        resources:
          limits:
            memory: 500Mi
          requests:
            cpu: 100m
            memory: 200Mi
        volumeMounts:
        - name: varlog
          mountPath: /var/log
        - name: varlibdockercontainers
          mountPath: /var/lib/docker/containers
          readOnly: true
        - name: config-volume
          mountPath: /etc/fluent/config.d
      nodeSelector:
        beta.kubernetes.io/fluentd-ds-ready: "true"
      tolerations:
      - key: node-role.kubernetes.io/master
        operator: Exists
        effect: NoSchedule
      terminationGracePeriodSeconds: 30
      volumes:
      - name: varlog
        hostPath:
          path: /var/log
      - name: varlibdockercontainers
        hostPath:
          path: /var/lib/docker/containers
      - name: config-volume
        configMap:
          name: fluentd-config

可以搜集/var/log和/var/log/containers和/var/lib/docker/containers内的日志
还可以搜集docker服务和kubelet服务的日志
为了能够灵活控制哪些节点的日志可以被收集，所以我们这里还添加了一个 nodSelector 属性

nodeSelector:
  beta.kubernetes.io/fluentd-ds-ready: "true"

所以要给所有节点打标签：
$ kubectl get node
$ kubectl label nodes server243.example.com beta.kubernetes.io/fluentd-ds-ready=true
$ kubectl get nodes --show-labels
由于我们的集群使用的是 kubeadm 搭建的，默认情况下 master 节点有污点，所以要想也收集 master 节点的日志，则需要添加上容忍

tolerations:
- key: node-role.kubernetes.io/master
  operator: Exists
  effect: NoSchedule

$ kubectl get pod -n logging
NAME READY STATUS RESTARTS AGE
es-cluster-0 1/1 Running 0 10h
es-cluster-1 1/1 Running 0 10h
es-cluster-2 1/1 Running 0 10h
fluentd-es-rf6p6 1/1 Running 0 9h
fluentd-es-s99r2 1/1 Running 0 9h
fluentd-es-snmtt 1/1 Running 0 9h
kibana-bd6f49775-qsxb2 1/1 Running 0 11h
3、在kibana上配置
http://192.168.1.243:32081
Create index pattern----第一步输入logstash-*，第二步选择@timestamp
4、创建测试pod，在kibana上查看日志

apiVersion: v1
kind: Pod
metadata:
  name: counter
spec:
  containers:
  - name: count
    image: busybox
    args: [/bin/sh, -c,
            'i=0; while true; do echo "$i: $(date)"; i=$((i+1)); sleep 1; done']

回到 Kibana Dashboard 页面，在上面的Discover页面搜索栏中输入kubernetes.pod_name:counter

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