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Fluentbit get Docker Logs(Systemd) in Kubernetes not working – CentOS

I’m trying to configure Fluentbit in Kubernetes to get Logs from application PODs/Docker Containers and send this log messages to Graylog using GELF format, but this is not working.

See my stack below:

INPUT

  • Docker version 1.13.1
    • Docker Log format => JSON
    • Docker Log Driver => Journald => systemd
  • Fluent-bit 1.3 running as Daemonset in Kubernetes
  • Kubernetes 1.17
  • OS Host: CentOS 7

OUTPUT

  • Message output format: GELF 1.1
  • Centralized log => Graylog 3

The problem is the fluentbit not read the log from systemd I’m not get any log in both outputs(Systemd,Stdout), the STDOUT is just to help in troubleshooting.

I don’t know why I’m not able to read from systemd.
I followed the documentation exactly
https://docs.fluentbit.io/manual/input/systemd

My K8S configurations:

fluent-bit-configmap.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: fluent-bit-config
  namespace: log
  labels:
    k8s-app: fluent-bit
data:
  # Configuration files: server, input, filters and output
  # ======================================================
  fluent-bit.conf: |
    [SERVICE]
      Flush         1
      Log_Level     debug
      Daemon        off

    @INCLUDE input-systemd.conf
    @INCLUDE output-stdout.conf

  input-systemd.conf: |
    [INPUT]
      Name            systemd
      Tag             host.*
      Parser          json
      Systemd_Filter  _SYSTEMD_UNIT=docker.service

  output-graylog.conf: |
    [OUTPUT]
      Name          gelf
      Match         *
      Host          10.142.15.214
      Port          12201
      Mode          tcp
      Gelf_Short_Message_Key log

  output-stdout.conf: |
    [OUTPUT]
      Name   stdout
      Match  *

fluent-bit-ds.yaml

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: fluent-bit
  namespace: log
  labels:
    k8s-app: fluent-bit-logging
    version: v1
    kubernetes.io/cluster-service: "true"
spec:
  selector:
    matchLabels:
      k8s-app: fluent-bit-logging
      version: v1
      kubernetes.io/cluster-service: "true"
  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:1.3.5
        imagePullPolicy: Always
        ports:
          - containerPort: 2020
        volumeMounts:
        - name: varlog
          mountPath: /var/log
        - name: varlibdockercontainers
          mountPath: /var/lib/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: /var/lib/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
      - operator: "Exists"
        effect: "NoExecute"
      - operator: "Exists"
        effect: "NoSchedule"

fluent-bit-role-binding.yaml

apiVersion: rbac.authorization.k8s.io/v1beta1
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: log

fluent-bit-role.yaml

apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: fluent-bit-read
rules:
- apiGroups: [""]
  resources:
  - namespaces
  - pods
  verbs: ["get", "list", "watch"]

fluent-bit-service-account.yaml

apiVersion: v1
kind: ServiceAccount
metadata:
  name: fluent-bit
  namespace: log

My Fluentbit OUTPUT(STDOUT) just for debug:

$ kubectl logs -f fluent-bit-2bzxb -n log


[2020/02/20 18:54:23] [Warning] [config] I cannot open /fluent-bit/etc/..2020_02_20_18_54_22.252769193/parsers_custom.conf file
[2020/02/20 18:54:23] [ info] [storage] initializing...
[2020/02/20 18:54:23] [ info] [storage] in-memory
[2020/02/20 18:54:23] [ info] [storage] normal synchronization mode, checksum disabled, max_chunks_up=128
[2020/02/20 18:54:23] [ info] [engine] started (pid=1)
[2020/02/20 18:54:23] [ info] [filter_kube] https=1 host=kubernetes.default.svc port=443
[2020/02/20 18:54:23] [ info] [filter_kube] local POD info OK
[2020/02/20 18:54:23] [ info] [filter_kube] testing connectivity with API server...
[2020/02/20 18:54:23] [ info] [filter_kube] API server connectivity OK
[2020/02/20 18:54:23] [ info] [sp] stream processor started

The problem is I’m not getting any log from systemd with this configuration

Tags:

3

Answers


  1. Chosen as BEST ANSWER
    0

    Thank you @edsiper I fix my Daemonset adding "path: /run/log"

    apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: fluent-bit
  namespace: log
  labels:
    k8s-app: fluent-bit-logging
    version: v1
    kubernetes.io/cluster-service: "true"
spec:
  selector:
    matchLabels:
      k8s-app: fluent-bit-logging
      version: v1
      kubernetes.io/cluster-service: "true"
  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:1.3.5
        imagePullPolicy: Always
        ports:
          - containerPort: 2020
        env:
        volumeMounts:
        - name: varlog
          mountPath: /var/log
        - name: varlibdockercontainers
          mountPath: /var/lib/docker/containers
          readOnly: true
        - name: systemdlog
          mountPath: /run/log
        - name: fluent-bit-config
          mountPath: /fluent-bit/etc/
      terminationGracePeriodSeconds: 10
      volumes:
      - name: varlog
        hostPath:
          path: /var/log
      - name: varlibdockercontainers
        hostPath:
          path: /var/lib/docker/containers
      - name: systemdlog
        hostPath:
          path: /run/log
      - name: fluent-bit-config
        configMap:
          name: fluent-bit-config
      serviceAccountName: fluent-bit
      tolerations:
      - key: node-role.kubernetes.io/master
        operator: Exists
        effect: NoSchedule
      - operator: "Exists"
        effect: "NoExecute"
      - operator: "Exists"
        effect: "NoSchedule"

  2. 0

    does your Fluent Bit container have access to the Systemd journal path ?

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  3. 0

    Not enough Karma to post a comment, so posting as an answer to @edsiper:
    "does your Fluent Bit container have access to the Systemd journal path ?"
    On default settings – no – it does not. When I tried to solve this problem I stumbled across this thread: https://github.com/fluent/fluent-bit/issues/497

    Long story short:

    1. you need to run fluent-bit container as root, since accessing the journal requires root permission

    2. set the machine id in docker to the same as in your root machine

    3. bind /run/log/journal:/run/log/journal
      so:

      fluent-bit:
   image: 'bitnami/fluent-bit:latest'
   restart: always
   user: root        #give root access
   network_mode: host
   command: /fluent-bit/bin/fluent-bit -c /fluent-bit/etc/fluent-bit.conf
   volumes:
      - ./service/config/fluent-bit.conf:/fluent-bit/etc/fluent-bit.conf
      - /etc/machine-id:/etc/machine-id:ro       #set the machine id
      - /run/log/journal:/run/log/journal        #give access to logs

    Then, in fluent-bit.conf you need edit the INPUT Path:

     [INPUT]
     Name            systemd
     Tag             *
     Path            /run/log/journal
     Systemd_Filter    _SYSTEMD_UNIT=docker.service
     Systemd_Filter    _SYSTEMD_UNIT=kubelet.service
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