Collect Logs with Fluentd in K8s. (Part-2)

Thanks for going through part-1 of this series, if not go check out that as well here EFK 7.4.0 Stack on Kubernetes. (Part-1). In this part, we will focus on solving our Log collection problem from docker containers inside the cluster. We will do so by deploying fluentd as DaemonSet inside our k8s cluster. DaemonSet ensures that all (or some) nodes run a copy of a pod in all worker nodes of K8s cluster.

In Kubernetes, containerized applications that log to stdout and stderr have their log streams captured and redirected to JSON files on the nodes. The Fluentd Pod will tail these log files, filter log events, transform the log data, and ship it off to the Elasticsearch cluster we deployed earlier.

In addition to container logs, the Fluentd agent will tail Kubernetes system component logs like kubelet, Kube-proxy, and Docker logs. To see a full list of sources tailed by the Fluentd logging agent, consult the kubernetes.conf file used to configure the logging agent.

Step-1 Service Account for Fluentd

First, we will create a Service Account called fluentd that the Fluentd Pods will use to access the Kubernetes API with ClusterRole and ClusterRoleBinding. We create it in the logging Namespace with label app: fluentd.

#fluentd-service-account.yaml
apiVersion: v1
kind: ServiceAccount
metadata:
  name: fluentd
  namespace: logging
  labels:
    app: fluentd
---
apiVersion: rbac.authorization.k8s.io/v1beta1
kind: ClusterRole
metadata:
  name: fluentd
  labels:
    app: fluentd
rules:
- apiGroups:
  - "*"
  resources:
  - pods
  - namespaces
  verbs:
  - get
  - list
  - watch
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1beta1
metadata:
  name: fluentd
roleRef:
  kind: ClusterRole
  name: fluentd
  apiGroup: rbac.authorization.k8s.io
subjects:
- kind: ServiceAccount
  name: fluentd
  namespace: logging

Step-2 Fluent Configuration as ConfigMap

Secondly, we’ll create a configMap fluentd-configmap,to provide a config file to our fluentd daemonset with all the required properties.

Here, we will be creating a “separate index for each namespace” to isolate the different environments. Optionally, user can create the index as per the different pods name as well in the K8s cluster.

Also, we will see how to “disable the index creation for certain namespaces & pods.”

#fluetd-configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: fluentd-configmap
  namespace: logging
  labels:
    app: fluentd
    kubernetes.io/cluster-service: "true"
data:
  fluent.conf: |
    <match fluent.**>
      @type null
    </match>
    <source>
      @type tail
      path /var/log/containers/*.log
# Here in exclude_path, we can define the path having the namespace name like prometheus, logging etc for which we don't want to create the indexes.
      exclude_path ["/var/log/containers/*prometheus*.log", "/var/log/containers/*logging*.log"]
      pos_file /var/log/fluentd-containers.log.pos
      time_format %Y-%m-%dT%H:%M:%S.%NZ
      tag kubernetes.*
      format json
      read_from_head false
    </source>
    <filter kubernetes.**>
      @type kubernetes_metadata
      verify_ssl false
    </filter>
    <match kubernetes.**>
        @type elasticsearch_dynamic
        include_tag_key true
        logstash_format true
#Below line is use to isolate the indexes as per different namespaces in K8s.
        logstash_prefix kubernetes-${record['kubernetes']['namespace_name']}
#Uncomment the below line, if want to isolate the indexes as per different pods in K8s.
        #logstash_prefix kubernetes-${record['kubernetes']['pod_name']}
        host "#{ENV['FLUENT_ELASTICSEARCH_HOST']}"
        port "#{ENV['FLUENT_ELASTICSEARCH_PORT']}"
        scheme "#{ENV['FLUENT_ELASTICSEARCH_SCHEME'] || 'http'}"
        user "#{ENV['FLUENT_ELASTICSEARCH_USER']}"
        password "#{ENV['FLUENT_ELASTICSEARCH_PASSWORD']}"
        reload_connections false
        reconnect_on_error true
        reload_on_failure true
        <buffer>
            flush_thread_count 16
            flush_interval 5s
            chunk_limit_size 2M
            queue_limit_length 32
            retry_max_interval 30
            retry_forever true
        </buffer>
    </matchΩ

Step-3 Fluentd as Daemonset

Now, we will deploy Fluentd as DaemonSet which allows to deploy an agent on each node of the k8s cluster to collect logs according to the settings configured in Step-2.

#fluentd-daemonset.yaml
apiVersion: extensions/v1beta1
kind: DaemonSet
metadata:
  name: fluentd
  namespace: logging
  labels:
    app: fluentd
    kubernetes.io/cluster-service: "true"
spec:
  selector:
    matchLabels:
      app: fluentd
      kubernetes.io/cluster-service: "true"
  template:
    metadata:
      labels:
        app: fluentd
        kubernetes.io/cluster-service: "true"
    spec:
      serviceAccount: fluentd
      containers:
      - name: fluentd
        image: fluent/fluentd-kubernetes-daemonset:v1.7.3-debian-elasticsearch7-1.0
        env:
          - name:  FLUENT_ELASTICSEARCH_HOST
            value: "elasticsearch.logging.svc.cluster.local"
          - name:  FLUENT_ELASTICSEARCH_PORT
            value: "9200"
          - name: FLUENT_ELASTICSEARCH_SCHEME
            value: "http"
          - name: FLUENT_ELASTICSEARCH_USER
            value: "elastic"
          - name: FLUENT_ELASTICSEARCH_PASSWORD
            valueFrom:
              secretKeyRef:
                name: efk-pw-elastic
                key: password
          - name: FLUENT_ELASTICSEARCH_SED_DISABLE
            value: "true"
        resources:
          limits:
            memory: 512Mi
          requests:
            cpu: 100m
            memory: 200Mi
        volumeMounts:
        - name: varlog
          mountPath: /var/log
        - name: varlibdockercontainers
          mountPath: /var/lib/docker/containers
          readOnly: true
        - name: fluentconfig
          mountPath: /fluentd/etc/fluent.conf
          subPath: fluent.conf
      terminationGracePeriodSeconds: 30
      volumes:
      - name: varlog
        hostPath:
          path: /var/log
      - name: varlibdockercontainers
        hostPath:
          path: /var/lib/docker/containers
      - name: fluentconfig
        configMap:
          name: fluentdconf

Step-4 Apply the files & see indexes in Kibana

We will apply all the configured files as below

kubectl apply -f fluentd-service-account.yaml \
              -f fluentd-configmap.yaml \
              -f fluentd-daemonset.yaml

Now, Open the Kibana Dashboard with admin user created in Part-1 and navigate to Management from Left bar and then click on Index management under Elasticsearch. Here you can see your indexes created with respect to the different namespaces in the K8s cluster.

Here, I am having indexes for 2 namespaces i.e. prod & Kube-system, rest others I have disabled.

3 thoughts on “Collect Logs with Fluentd in K8s. (Part-2)”

Hi Jaspreet, can you please prepare one more article on Fluentd for openshift cluster. how we will install Fluentd in OCP nodes as a log collector and it will collect logs from OCP nodes ,then it feed to Elasticsearch and it will show in Kibana dashboard.

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