前言

收集日志的组件多不胜数，有ELK久负盛名组合中的logstash, 也有EFK组合中的filebeat,更有cncf新贵fluentd,另外还有大数据领域使用比较多的flume。本次主要说另外一种，和fluentd一脉相承的fluent bit。

Fluent Bit是一个开源和多平台的Log Processor and Forwarder，它允许您从不同的来源收集数据/日志，统一并将它们发送到多个目的地。它与Docker和Kubernetes环境完全兼容。Fluent Bit用C语言编写，具有可插拔的架构，支持大约30个扩展。它快速轻便，通过TLS为网络运营提供所需的安全性。

之所以选择fluent bit，看重了它的高性能。下面是官方贴出的一张与fluentd对比图：

在已经拥有的插件满足需求和场景的前提下，fluent bit无疑是一个很好的选择。

fluent bit 简介

在使用的这段时间之后，总结以下几点优点：

• 支持routing,适合多output的场景。比如有些业务日志，或写入到es中，供查询。或写入到hdfs中，供大数据进行分析。
• fliter支持lua。对于那些对c语言hold不住的团队，可以用lua写自己的filter。
• output 除了官方已经支持的十几种，还支持用golang写output。例如：fluent-bit-kafka-output-plugin

k8s日志收集

k8s日志分析

主要讲kubeadm部署的k8s集群。日志主要有：

• kubelet和etcd的日志，一般采用systemd部署，自然而然就是要支持systemd格式日志的采集。filebeat并不支持该类型。
• kube-apiserver等组件stderr和stdout日志，这个一般输出的格式取决于docker的日志驱动，一般为json-file。
• 业务落盘的日志。支持tail文件的采集组件都满足。这点不在今天的讨论范围之内。

部署方案

fluent bit 采取DaemonSet部署。 如下图：

部署yaml

---

apiVersion: v1
kind: Service
metadata:
  name: elasticsearch-logging
  namespace: kube-system
  labels:
    k8s-app: elasticsearch-logging
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
    kubernetes.io/name: "Elasticsearch"
spec:
  ports:
  - port: 9200
    protocol: TCP
    targetPort: db
  selector:
    k8s-app: elasticsearch-logging

---

# RBAC authn and authz
apiVersion: v1
kind: ServiceAccount
metadata:
  name: elasticsearch-logging
  namespace: kube-system
  labels:
    k8s-app: elasticsearch-logging
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: elasticsearch-logging
  labels:
    k8s-app: elasticsearch-logging
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
rules:
- apiGroups:
  - ""
  resources:
  - "services"
  - "namespaces"
  - "endpoints"
  verbs:
  - "get"
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  namespace: kube-system
  name: elasticsearch-logging
  labels:
    k8s-app: elasticsearch-logging
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
subjects:
- kind: ServiceAccount
  name: elasticsearch-logging
  namespace: kube-system
  apiGroup: ""
roleRef:
  kind: ClusterRole
  name: elasticsearch-logging
  apiGroup: ""
---
# Elasticsearch deployment itself
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: elasticsearch-logging
  namespace: kube-system
  labels:
    k8s-app: elasticsearch-logging
    version: v6.3.0
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
spec:
  serviceName: elasticsearch-logging
  replicas: 2
  selector:
    matchLabels:
      k8s-app: elasticsearch-logging
      version: v6.3.0
  template:
    metadata:
      labels:
        k8s-app: elasticsearch-logging
        version: v6.3.0
        kubernetes.io/cluster-service: "true"
    spec:
      serviceAccountName: elasticsearch-logging
      containers:
      - image: k8s.gcr.io/elasticsearch:v6.3.0
        name: elasticsearch-logging
        resources:
          # need more cpu upon initialization, therefore burstable class
          limits:
            cpu: 1000m
          requests:
            cpu: 100m
        ports:
        - containerPort: 9200
          name: db
          protocol: TCP
        - containerPort: 9300
          name: transport
          protocol: TCP
        volumeMounts:
        - name: elasticsearch-logging
          mountPath: /data
        env:
        - name: "NAMESPACE"
          valueFrom:
            fieldRef:
              fieldPath: metadata.namespace
      # Elasticsearch requires vm.max_map_count to be at least 262144.
      # If your OS already sets up this number to a higher value, feel free
      # to remove this init container.
      initContainers:
      - image: alpine:3.6
        command: ["/sbin/sysctl", "-w", "vm.max_map_count=262144"]
        name: elasticsearch-logging-init
        securityContext:
          privileged: true
  volumeClaimTemplates:
  - metadata:
      name: elasticsearch-logging
      annotations:
        volume.beta.kubernetes.io/storage-class: gp2
    spec:
      accessModes:
        - "ReadWriteOnce"
      resources:
        requests:
          storage: 10Gi

---
apiVersion: v1
kind: ConfigMap
metadata:
  name: fluent-bit-config
  namespace: kube-system
  labels:
    k8s-app: fluent-bit
data:
  # Configuration files: server, input, filters and output
  # ======================================================
  fluent-bit.conf: |
    [SERVICE]
        Flush         1
        Log_Level     info
        Daemon        off
        Parsers_File  parsers.conf
        HTTP_Server   On
        HTTP_Listen   0.0.0.0
        HTTP_Port     2020

    @INCLUDE input-kubernetes.conf
    @INCLUDE filter-kubernetes.conf
    @INCLUDE output-elasticsearch.conf

  input-kubernetes.conf: |
    [INPUT]
        Name              tail
        Tag               kube.*
        Path              /var/log/containers/*.log
        Parser            docker
        DB                /var/log/flb_kube.db
        Mem_Buf_Limit     5MB
        Skip_Long_Lines   On
        Refresh_Interval  10

    [INPUT]
        Name           systemd
        Tag             host.*
        Systemd_Filter  _SYSTEMD_UNIT=kubelet.service
        Path            /var/log/journal
        DB              /var/log/flb_host.db

  filter-kubernetes.conf: |
    [FILTER]
        Name                kubernetes
        Match               kube.*
        Kube_URL            https://kubernetes.default.svc.cluster.local:443
        Merge_Log           On
        K8S-Logging.Parser  On
        K8S-Logging.Exclude On
    [FILTER]
        Name                kubernetes
        Match               host.*
        Kube_URL            https://kubernetes.default.svc.cluster.local:443
        Merge_Log           On
        Use_Journal         On

  output-elasticsearch.conf: |
    [OUTPUT]
        Name            es
        Match           *
        Host            ${FLUENT_ELASTICSEARCH_HOST}
        Port            ${FLUENT_ELASTICSEARCH_PORT}
        Logstash_Format On
        Retry_Limit     False

  parsers.conf: |
    [PARSER]
        Name   apache
        Format regex
        Regex  ^(?<host>[^ ]*) [^ ]* (?<user>[^ ]*) \[(?<time>[^\]]*)\] "(?<method>\S+)(?: +(?<path>[^\"]*?)(?: +\S*)?)?" (?<code>[^ ]*) (?<size>[^ ]*)(?: "(?<referer>[^\"]*)" "(?<agent>[^\"]*)")?$
        Time_Key time
        Time_Format %d/%b/%Y:%H:%M:%S %z

    [PARSER]
        Name   apache2
        Format regex
        Regex  ^(?<host>[^ ]*) [^ ]* (?<user>[^ ]*) \[(?<time>[^\]]*)\] "(?<method>\S+)(?: +(?<path>[^ ]*) +\S*)?" (?<code>[^ ]*) (?<size>[^ ]*)(?: "(?<referer>[^\"]*)" "(?<agent>[^\"]*)")?$
        Time_Key time
        Time_Format %d/%b/%Y:%H:%M:%S %z

    [PARSER]
        Name   apache_error
        Format regex
        Regex  ^\[[^ ]* (?<time>[^\]]*)\] \[(?<level>[^\]]*)\](?: \[pid (?<pid>[^\]]*)\])?( \[client (?<client>[^\]]*)\])? (?<message>.*)$

    [PARSER]
        Name   nginx
        Format regex
        Regex ^(?<remote>[^ ]*) (?<host>[^ ]*) (?<user>[^ ]*) \[(?<time>[^\]]*)\] "(?<method>\S+)(?: +(?<path>[^\"]*?)(?: +\S*)?)?" (?<code>[^ ]*) (?<size>[^ ]*)(?: "(?<referer>[^\"]*)" "(?<agent>[^\"]*)")?$
        Time_Key time
        Time_Format %d/%b/%Y:%H:%M:%S %z

    [PARSER]
        Name   json
        Format json
        Time_Key time
        Time_Format %d/%b/%Y:%H:%M:%S %z

    [PARSER]
        Name        docker
        Format      json
        Time_Key    time
        Time_Format %Y-%m-%dT%H:%M:%S.%L
        Time_Keep   On
        # Command      |  Decoder | Field | Optional Action
        # =============|==================|=================
        Decode_Field_As   escaped    log

    [PARSER]
        Name        syslog
        Format      regex
        Regex       ^\<(?<pri>[0-9]+)\>(?<time>[^ ]* {1,2}[^ ]* [^ ]*) (?<host>[^ ]*) (?<ident>[a-zA-Z0-9_\/\.\-]*)(?:\[(?<pid>[0-9]+)\])?(?:[^\:]*\:)? *(?<message>.*)$
        Time_Key    time
        Time_Format %b %d %H:%M:%S

---

apiVersion: extensions/v1beta1
kind: DaemonSet
metadata:
  name: fluent-bit
  namespace: kube-system
  labels:
    k8s-app: fluent-bit-logging
    version: v1
    kubernetes.io/cluster-service: "true"
spec:
  template:
    metadata:
      labels:
        k8s-app: fluent-bit-logging
        version: v1
        kubernetes.io/cluster-service: "true"
      annotations:
        prometheus.io/scrape: "true"
        prometheus.io/port: "2020"
        prometheus.io/path: /api/v1/metrics/prometheus
    spec:
      containers:
      - name: fluent-bit
        image: fluent/fluent-bit:1.0.0
        imagePullPolicy: Always
        ports:
          - containerPort: 2020
        env:
        - name: FLUENT_ELASTICSEARCH_HOST
          value: "elasticsearch-logging"
        - name: FLUENT_ELASTICSEARCH_PORT
          value: "9200"
        volumeMounts:
        - name: varlog
          mountPath: /var/log
        - name: varlibdockercontainers
          mountPath: /data/docker/containers
          readOnly: true
        - name: fluent-bit-config
          mountPath: /fluent-bit/etc/
      terminationGracePeriodSeconds: 10
      volumes:
      - name: varlog
        hostPath:
          path: /var/log
      - name: varlibdockercontainers
        hostPath:
          path: /data/docker/containers
      - name: fluent-bit-config
        configMap:
          name: fluent-bit-config
      serviceAccountName: fluent-bit
      tolerations:
      - key: node-role.kubernetes.io/master
        operator: Exists
        effect: NoSchedule

---

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: fluent-bit-read
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: fluent-bit-read
subjects:
- kind: ServiceAccount
  name: fluent-bit
  namespace: kube-system

---

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: fluent-bit-read
rules:
- apiGroups: [""]
  resources:
  - namespaces
  - pods
  verbs: ["get", "list", "watch"]

---


apiVersion: v1
kind: ServiceAccount
metadata:
  name: fluent-bit
  namespace: kube-system

---

apiVersion: apps/v1
kind: Deployment
metadata:
  name: kibana-logging
  namespace: kube-system
  labels:
    k8s-app: kibana-logging
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
spec:
  replicas: 1
  selector:
    matchLabels:
      k8s-app: kibana-logging
  template:
    metadata:
      labels:
        k8s-app: kibana-logging
      annotations:
        seccomp.security.alpha.kubernetes.io/pod: 'docker/default'
    spec:
      containers:
      - name: kibana-logging
        image: docker.elastic.co/kibana/kibana-oss:6.3.2
        resources:
          # need more cpu upon initialization, therefore burstable class
          limits:
            cpu: 1000m
          requests:
            cpu: 100m
        env:
          - name: ELASTICSEARCH_URL
            value: http://elasticsearch-logging:9200
        ports:
        - containerPort: 5601
          name: ui
          protocol: TCP


---

apiVersion: v1
kind: Service
metadata:
  name: kibana-logging
  namespace: kube-system
  labels:
    k8s-app: kibana-logging
    kubernetes.io/cluster-service: "true"
    addonmanager.kubernetes.io/mode: Reconcile
    kubernetes.io/name: "Kibana"
  annotations:
    service.beta.kubernetes.io/aws-load-balancer-type: nlb
spec:
  ports:
  - port: 5601
    protocol: TCP
    targetPort: ui
  selector:
    k8s-app: kibana-logging
  type: LoadBalancer

---

总结

真实场景的日志收集比较复杂，在日志量大的情况下，一般要引入kafka。
此外关于注意日志的lograte。一般来说，docker是支持该功能的。可以通过下面的配置解决：

cat >  /etc/docker/daemon.json <<EOF
{
 "log-opts": {
    "max-size": "100m",
    "max-file": "3"
  }
}
EOF

在k8s中运行的业务日志，不仅要考虑清除过时的日志，还要考虑新增pod的日志的收集。这个时候,往往需要在fluent bit上面再包一层逻辑，获取需要收集的日志路径。比如log-pilot。