Container logging architecture in Kubernetes - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the logging driver for a Docker container.

Kubernetes

docker run --log-driver=[1] nginx

Drag options to blanks, or click blank then click option'

Ajson-file

Bsyslog

Cnone

Djournald

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a logging driver that disables logging like 'none'.

Using a system logging driver when the default is expected.

The json-file driver is the default logging driver for Docker containers, storing logs as JSON files on the host.

2fill in blank

medium

Complete the command to view logs of a Kubernetes pod named 'webapp'.

Kubernetes

kubectl logs [1]

Drag options to blanks, or click blank then click option'

Adeployment/webapp

Bpod/webapp

Cservice/webapp

Dnode/webapp

Attempts:

3 left

💡 Hint

Common Mistakes

Using deployment or service names instead of pod names.

Trying to get logs from nodes directly.

The kubectl logs command requires the pod name, so pod/webapp is correct.

3fill in blank

hard

Fix the error in the Fluentd configuration snippet to collect container logs from the correct path.

Kubernetes

<source>
  @type tail
  path [1]
  pos_file /var/log/fluentd-containers.log.pos
  tag kubernetes.*
  format json
</source>

Drag options to blanks, or click blank then click option'

A/var/log/syslog

B/var/log/pods/*.log

C/var/log/docker/*.log

D/var/log/containers/*.log

Attempts:

3 left

💡 Hint

Common Mistakes

Using pod log paths instead of container log paths.

Using system log paths like syslog.

Fluentd collects container logs from /var/log/containers/*.log in Kubernetes environments.

4fill in blank

hard

Fill both blanks to create a Kubernetes DaemonSet manifest snippet that deploys a logging agent on all nodes.

Kubernetes

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: fluentd
spec:
  selector:
    matchLabels:
      name: fluentd
  template:
    metadata:
      labels:
        name: fluentd
    spec:
      containers:
      - name: fluentd
        image: fluentd:latest
        volumeMounts:
        - name: varlog
          mountPath: [1]
      volumes:
      - name: varlog
        hostPath:
          path: [2]

Drag options to blanks, or click blank then click option'

A/var/log/containers

B/var/log/pods

C/var/log

D/var/lib/docker/containers

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up container mount path and host path.

Using pod log paths instead of container log paths.

The logging agent mounts /var/log inside the container and maps it to /var/log on the host to access container logs.

5fill in blank

hard

Fill all three blanks to define a Kubernetes ConfigMap for Fluentd with a filter to add Kubernetes metadata.

Kubernetes

apiVersion: v1
kind: ConfigMap
metadata:
  name: fluentd-config
data:
  fluent.conf: |
    <filter kubernetes.**>
      @type [1]
      kubernetes_url [2]
      cache_size [3]
    </filter>

Drag options to blanks, or click blank then click option'

Akubernetes_metadata

Bhttps://kubernetes.default.svc

C1000

Drecord_transformer

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong filter types like record_transformer.

Incorrect Kubernetes API URL.

Setting cache_size to a non-numeric value.

The filter type is kubernetes_metadata to enrich logs with Kubernetes info. The URL points to the Kubernetes API server, and cache_size controls metadata caching.

Practice

1. In Kubernetes, where do containers typically write their logs?

easy

A. Directly to files inside the container's filesystem

B. To a database inside the container

C. To a remote logging server

D. To stdout and stderr streams

Solution

1. Step 1: Understand container logging basics

   Containers are designed to write logs to standard output (stdout) and standard error (stderr) streams instead of files inside the container.

2. Step 2: Recall Kubernetes logging capture method

   Kubernetes captures these stdout and stderr streams from containers to manage logs effectively.

3. Final Answer:

   To stdout and stderr streams -> Option D

4. Quick Check:

   Container logs = stdout/stderr [OK]

Hint: Remember containers log to stdout/stderr, not files [OK]

Common Mistakes:

• Thinking logs are stored inside container files
• Assuming logs go directly to remote servers
• Confusing stdout/stderr with database logging

2. Which of the following is the correct way Kubernetes stores container logs on a node?

easy

A. As log files under /var/log/containers directory on the node

B. In a centralized database on the master node

C. Inside the container's writable layer

D. In memory only, not persisted on disk

Solution

1. Step 1: Identify Kubernetes node log storage

   Kubernetes stores container logs as files on the node, typically under the /var/log/containers directory.

2. Step 2: Eliminate incorrect options

   Logs are not stored in a centralized database on the master, nor inside the container writable layer, and they are persisted on disk, not just in memory.

3. Final Answer:

   As log files under /var/log/containers directory on the node -> Option A

4. Quick Check:

   Node logs path = /var/log/containers [OK]

Hint: Kubernetes logs are files under /var/log/containers on nodes [OK]

Common Mistakes:

• Assuming logs are stored only in memory
• Thinking logs are inside container writable layer
• Believing logs are centralized on master node

3. Given a Kubernetes cluster with a logging agent running on each node, what is the primary role of this agent?

medium

A. To collect container logs from node files and send them to a central system

B. To create log files inside each container

C. To delete old logs from the container filesystem

D. To restart containers when logs grow too large

Solution

1. Step 1: Understand logging agent function

   Logging agents run on nodes to gather logs from container log files stored on the node.

2. Step 2: Identify agent's purpose

   The agent sends collected logs to a central logging system for easy access and analysis.

3. Final Answer:

   To collect container logs from node files and send them to a central system -> Option A

4. Quick Check:

   Logging agent = collect and forward logs [OK]

Hint: Logging agents gather and forward logs to central systems [OK]

Common Mistakes:

• Thinking agents create logs inside containers
• Assuming agents delete logs automatically
• Believing agents restart containers based on log size

4. You notice that your Kubernetes logging agent is not forwarding logs to the central system. Which of the following is the most likely cause?

medium

A. Containers are writing logs to stdout/stderr

B. The logging agent cannot access the /var/log/containers directory on the node

C. The central logging system is storing logs on the node

D. Kubernetes does not support logging agents

Solution

1. Step 1: Analyze logging agent failure

   If the agent cannot access the node's log directory, it cannot read logs to forward them.

2. Step 2: Check other options for correctness

   Containers writing to stdout/stderr is normal; Kubernetes supports logging agents; central system storing logs on node is unrelated to forwarding failure.

3. Final Answer:

   The logging agent cannot access the /var/log/containers directory on the node -> Option B

4. Quick Check:

   Agent access to logs = critical [OK]

Hint: Check logging agent's access to node log files first [OK]

Common Mistakes:

• Blaming containers writing to stdout/stderr
• Assuming Kubernetes lacks logging agent support
• Confusing central system storage with forwarding issues

5. You want to implement a centralized logging solution in Kubernetes. Which combination correctly describes the container logging flow?

hard

A. Containers write logs to stdout/stderr -> Kubernetes stores logs in etcd -> Logging agent collects logs from etcd

B. Containers write logs to files inside container -> Kubernetes copies files to master -> Logging agent forwards logs

C. Containers write logs to stdout/stderr -> Kubernetes stores logs on node -> Logging agent collects and forwards logs

D. Containers send logs directly to central server -> Kubernetes stores logs on node -> Logging agent deletes logs

Solution

1. Step 1: Understand container log writing

   Containers write logs to stdout/stderr streams, not files inside the container.

2. Step 2: Trace Kubernetes log handling

   Kubernetes captures these logs and stores them as files on the node.

3. Step 3: Identify logging agent role

   Logging agents collect these node log files and forward them to a central logging system.

4. Final Answer:

   Containers write logs to stdout/stderr -> Kubernetes stores logs on node -> Logging agent collects and forwards logs -> Option C

5. Quick Check:

   Logging flow = stdout -> node files -> agent -> central [OK]

Hint: Follow logs: stdout -> node storage -> agent -> central system [OK]

Common Mistakes:

• Thinking logs are stored in etcd
• Assuming containers write logs to files inside container
• Believing logging agent deletes logs