Container logging architecture in Kubernetes - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding container log storage locations

Where does Kubernetes typically store container logs on the node by default?

A /home/user/.kube/logs directory

B /etc/kubernetes/logs directory

C /usr/local/bin/logs directory

D /var/log/containers directory

💡 Hint

Think about where Docker or container runtimes write logs on the host.

Kubernetes stores container logs in the /var/log/containers directory on the node by default. This directory contains symlinks to the actual log files managed by the container runtime.

💻 Command Output

intermediate

Output of kubectl logs command

What is the output of the command kubectl logs my-pod if the pod has a container that writes 'Hello World' to stdout?

A Error: pod not found

B No logs found for container

C Hello World

D kubectl: command not found

💡 Hint

This command shows the container's standard output logs.

The kubectl logs command fetches the logs from the container's stdout and stderr streams. If the container wrote 'Hello World', that text will appear as output.

❓ Configuration

advanced

Configuring a Fluentd DaemonSet for cluster-wide logging

Which configuration snippet correctly deploys Fluentd as a DaemonSet to collect logs from all nodes?

A

apiVersion: apps/v1
kind: Deployment
metadata:
  name: fluentd
spec:
  replicas: 3
  selector:
    matchLabels:
      name: fluentd
  template:
    metadata:
      labels:
        name: fluentd
    spec:
      containers:
      - name: fluentd
        image: fluent/fluentd
        volumeMounts:
        - name: varlog
          mountPath: /var/log
      volumes:
      - name: varlog
        hostPath:
          path: /var/log

B

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: fluentd
spec:
  selector:
    matchLabels:
      name: fluentd
  template:
    metadata:
      labels:
        name: fluentd
    spec:
      containers:
      - name: fluentd
        image: fluent/fluentd
        volumeMounts:
        - name: varlog
          mountPath: /var/log
      volumes:
      - name: varlog
        hostPath:
          path: /var/log

C

apiVersion: v1
kind: Pod
metadata:
  name: fluentd
spec:
  containers:
  - name: fluentd
    image: fluent/fluentd
    volumeMounts:
    - name: varlog
      mountPath: /var/log
  volumes:
  - name: varlog
    hostPath:
      path: /var/log

D

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: fluentd
spec:
  selector:
    matchLabels:
      name: fluentd
  serviceName: fluentd
  replicas: 1
  template:
    metadata:
      labels:
        name: fluentd
    spec:
      containers:
      - name: fluentd
        image: fluent/fluentd
        volumeMounts:
        - name: varlog
          mountPath: /var/log
      volumes:
      - name: varlog
        hostPath:
          path: /var/log

💡 Hint

DaemonSets run one pod per node to collect logs from all nodes.

Option B correctly defines a DaemonSet with a container mounting the host's /var/log directory to collect logs from all nodes. Other options use Pod, Deployment, or StatefulSet which do not guarantee one pod per node.

❓ Troubleshoot

advanced

Diagnosing missing logs in Kubernetes cluster

You notice that kubectl logs returns empty output for a pod, but the application writes logs to stdout. What is the most likely cause?

A The container runtime is not writing logs to the expected location

B The pod is running on a node without network connectivity

C The pod's container image is missing the logging library

D The Kubernetes API server is down

💡 Hint

Think about where logs come from when you run kubectl logs.

kubectl logs fetches logs from the container runtime's log files. If the runtime is not writing logs properly, the command returns empty output even if the app writes to stdout.

🔀 Workflow

expert

Order of steps to implement centralized logging in Kubernetes

Arrange the steps in the correct order to set up centralized logging for a Kubernetes cluster using Fluentd and Elasticsearch.

A 3,2,1,4

B 2,3,1,4

C 3,1,2,4

D 1,3,2,4

💡 Hint

Think about creating a clean space first, then collecting logs, storing them, and finally visualizing.

First create a namespace to organize logging components (3). Then deploy Fluentd as a DaemonSet to collect logs (2). Next deploy Elasticsearch to store logs (1). Finally set up Kibana to visualize logs (4).