Centralized logging setup in Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the logging driver in a Docker run command.

Docker

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

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

Ajson-file

Bsyslog

Cnone

Dlocal

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'syslog' without configuring a syslog server

Using 'none' disables logging

The json-file driver is the default Docker logging driver that stores logs as JSON files on the host.

2fill in blank

medium

Complete the Docker Compose service to use the syslog logging driver.

Docker

services:
  app:
    image: myapp
    logging:
      driver: [1]

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

Asyslog

Bjournald

Cfluentd

Djson-file

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'json-file' which stores logs locally

Choosing 'fluentd' without a Fluentd server configured

The syslog driver sends container logs to the syslog daemon on the host or a remote syslog server.

3fill in blank

hard

Fix the error in the Docker daemon.json configuration to enable centralized logging with Fluentd.

Docker

{
  "log-driver": "[1]",
  "log-opts": {
    "fluentd-address": "localhost:24224"
  }
}

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

Asyslog

Bnone

Cjson-file

Dfluentd

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'json-file' which stores logs locally

Using 'none' disables logging

The fluentd log driver sends logs to a Fluentd collector, which is useful for centralized logging setups.

4fill in blank

hard

Fill both blanks to configure Docker Compose to send logs to a remote syslog server with a tag.

Docker

services:
  web:
    image: nginx
    logging:
      driver: [1]
      options:
        syslog-address: [2]

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

Asyslog

Bfluentd

Ctcp://192.168.1.100:514

Dudp://192.168.1.100:514

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'fluentd' driver with syslog address

Using TCP address without matching driver

Using the syslog driver with a udp:// address sends logs to a remote syslog server over UDP.

5fill in blank

hard

Fill all three blanks to create a Docker Compose logging config that sends logs to Fluentd with a custom tag.

Docker

services:
  backend:
    image: mybackend
    logging:
      driver: [1]
      options:
        fluentd-address: [2]
        tag: [3]

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

Asyslog

Bfluentd

Cbackend.logs

Dlocalhost:24224

Attempts:

3 left

💡 Hint

Common Mistakes

Using syslog driver with fluentd options

Incorrect tag format

The fluentd driver sends logs to the Fluentd collector at localhost:24224 with a custom tag backend.logs for filtering.

Practice

1. What is the main purpose of using a centralized logging setup in Docker?

easy

A. To reduce the size of container images

B. To increase container startup speed

C. To collect logs from multiple containers in one place for easier monitoring

D. To automatically restart containers on failure

Solution

1. Step 1: Understand centralized logging concept

   Centralized logging means gathering logs from many containers into a single location.

2. Step 2: Identify the benefit

   This helps in easier monitoring and troubleshooting by having all logs accessible in one place.

3. Final Answer:

   To collect logs from multiple containers in one place for easier monitoring -> Option C

4. Quick Check:

   Centralized logging = collect logs centrally [OK]

Hint: Centralized logging means one place for all container logs [OK]

Common Mistakes:

• Confusing logging with container performance
• Thinking it reduces image size
• Assuming it restarts containers automatically

2. Which Docker command option correctly sets the log driver to Fluentd for a container?

easy

A. docker run --log-driver fluentd myimage

B. docker run --log-driver=fluentd myimage

C. docker run --log-driver:fluentd myimage

D. docker run --logdriver=fluentd myimage

Solution

1. Step 1: Recall Docker log driver syntax

   The correct syntax uses double dashes and equals sign: --log-driver=drivername

2. Step 2: Match the option

   docker run --log-driver=fluentd myimage uses --log-driver=fluentd which is correct syntax for setting Fluentd as log driver.

3. Final Answer:

   docker run --log-driver=fluentd myimage -> Option B

4. Quick Check:

   Correct syntax uses '=' after --log-driver [OK]

Hint: Use --log-driver=drivername with equals sign [OK]

Common Mistakes:

• Using space instead of '=' after --log-driver
• Using colon ':' instead of '='
• Misspelling option name

3. Given the command:

docker run --log-driver=fluentd --log-opt fluentd-address=localhost:24224 myapp

What will happen to the container logs?

medium

A. Logs will be sent to a Fluentd server running on localhost port 24224

B. Logs will be stored only inside the container

C. Logs will be sent to Docker's default json-file driver

D. Container will fail to start due to invalid log options

Solution

1. Step 1: Analyze log driver and options

   The command sets log driver to fluentd and specifies fluentd-address as localhost:24224.

2. Step 2: Understand effect on logs

   Logs will be forwarded to the Fluentd server at the given address instead of default storage.

3. Final Answer:

   Logs will be sent to a Fluentd server running on localhost port 24224 -> Option A

4. Quick Check:

   Fluentd driver + address = logs sent to Fluentd [OK]

Hint: Fluentd log driver sends logs to specified Fluentd address [OK]

Common Mistakes:

• Assuming logs stay inside container
• Thinking default json-file driver is used
• Believing the command causes failure

4. You tried to run:

docker run --log-driver=fluentd --log-opt fluentd-address=localhost:24224 myapp

but logs are not appearing in Fluentd. What is a likely cause?

medium

A. The container image 'myapp' does not support logging

B. The --log-driver option must be set after the image name

C. Docker does not support Fluentd as a log driver

D. Fluentd server is not running or unreachable at localhost:24224

Solution

1. Step 1: Check Fluentd server availability

   If Fluentd server is not running or unreachable at the specified address, logs won't be received.

2. Step 2: Verify Docker and options correctness

   Docker supports Fluentd log driver and the command syntax is correct, so these are unlikely causes.

3. Final Answer:

   Fluentd server is not running or unreachable at localhost:24224 -> Option D

4. Quick Check:

   Fluentd server must be running to receive logs [OK]

Hint: Check Fluentd server is running and reachable [OK]

Common Mistakes:

• Blaming container image for logging issues
• Thinking Docker lacks Fluentd support
• Misplacing --log-driver option

5. You want to centralize logs from multiple Docker containers using syslog. Which is the correct way to run a container to send logs to a syslog server at 192.168.1.100 port 514?

hard

A. docker run --log-driver=syslog --log-opt syslog-address=udp://192.168.1.100:514 myapp

B. docker run --log-driver=json-file --log-opt syslog-address=tcp://192.168.1.100:514 myapp

C. docker run --log-driver=fluentd --log-opt syslog-address=udp://192.168.1.100:514 myapp

D. docker run --log-driver=syslog --log-opt syslog-address=tcp://192.168.1.100:514 myapp

Solution

1. Step 1: Identify correct log driver for syslog

   Use --log-driver=syslog to send logs to a syslog server.

2. Step 2: Choose correct syslog protocol and address

   Syslog commonly uses UDP protocol, so syslog-address=udp://192.168.1.100:514 is correct.

3. Step 3: Verify options match

   docker run --log-driver=syslog --log-opt syslog-address=udp://192.168.1.100:514 myapp correctly sets syslog driver and UDP address; others use wrong driver or protocol.

4. Final Answer:

   docker run --log-driver=syslog --log-opt syslog-address=udp://192.168.1.100:514 myapp -> Option A

5. Quick Check:

   Syslog driver + UDP address = correct syslog logging [OK]

Hint: Syslog driver with udp:// address sends logs correctly [OK]

Common Mistakes:

• Using TCP instead of UDP for syslog
• Mixing Fluentd driver with syslog options
• Using json-file driver for centralized logging