Docker deployment for Vue apps - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What will be the output when running this Dockerfile for a Vue app?

Consider this Dockerfile for a Vue app. What will be the final behavior of the container when started?

Vue

FROM node:18-alpine AS build
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
RUN npm run build

FROM nginx:stable-alpine
COPY --from=build /app/dist /usr/share/nginx/html
EXPOSE 80
CMD ["nginx", "-g", "daemon off;"]

A The container serves the built Vue app on port 80 using nginx.

B The container serves the Vue app but on port 3000 instead of 80.

C The container fails because npm install is missing in the second stage.

D The container runs the Vue app in development mode with hot reload on port 80.

💡 Hint

Think about what the two stages in the Dockerfile do and what nginx serves.

The first stage builds the Vue app into static files in /app/dist. The second stage copies these files into nginx's default html folder and serves them on port 80.

📝 Syntax

intermediate

Which Dockerfile snippet correctly copies the Vue build output to nginx?

You want to copy the Vue app build output from the build stage to nginx's html folder. Which COPY command is correct?

A COPY /app/dist /usr/share/nginx/html

B COPY --from=build /dist /usr/share/nginx/html

C COPY --from=build /app/build /usr/share/nginx/html

D COPY --from=build /app/dist /usr/share/nginx/html

💡 Hint

Remember the build output folder inside the build stage.

The Vue build output is in /app/dist inside the build stage. The COPY command must specify the source stage and the correct path.

🔧 Debug

advanced

Why does this Docker container fail to serve the Vue app?

Given this Dockerfile snippet, the container starts but shows a 404 error when accessed: FROM node:18-alpine AS build WORKDIR /app COPY package*.json ./ RUN npm install COPY . . RUN npm run build FROM nginx:stable-alpine COPY --from=build /app /usr/share/nginx/html EXPOSE 80 CMD ["nginx", "-g", "daemon off;"]

A The EXPOSE 80 command is missing, so port 80 is not open.

B The npm install command is missing, so build fails silently.

C The entire /app folder is copied instead of only /app/dist, so nginx serves wrong files.

D The CMD command is incorrect and nginx never starts.

💡 Hint

Check what nginx expects to serve and what files are copied.

Nginx serves static files from /usr/share/nginx/html. Copying the entire /app folder includes source files and node_modules, not just the built static files in /app/dist. This causes nginx to serve wrong content and results in 404 errors.

❓ state_output

advanced

What environment variable should you set to change the base URL in a Vue app Docker build?

You want your Vue app to work correctly behind a subpath like /myapp/. Which environment variable should you set during build to adjust the base URL?

A VUE_APP_PUBLIC_PATH

B BASE_URL

C PUBLIC_PATH

D VUE_APP_BASE_URL

💡 Hint

Check Vue CLI documentation about base URL configuration.

Vue CLI uses the environment variable BASE_URL to set the base path for the app during build. This affects how assets and routing paths are generated.

🧠 Conceptual

expert

Why use a multi-stage Docker build for Vue apps instead of a single stage?

What is the main advantage of using a multi-stage Dockerfile with a build stage and a separate nginx stage for deploying Vue apps?

A It reduces the final image size by excluding development dependencies and build tools.

B It allows running the Vue app in development mode inside the container.

C It enables hot module replacement in production containers.

D It automatically updates the Vue app when source files change.

💡 Hint

Think about what files are needed to run the app versus build it.

Multi-stage builds let you use a full Node environment to build the app, then copy only the static files to a lightweight nginx image. This keeps the final image small and secure.

Practice

1. What is the main purpose of using Docker for deploying a Vue app?

easy

A. To write Vue components faster

B. To replace Vue Router in the app

C. To package the app and its environment for consistent deployment

D. To automatically generate Vue templates

Solution

1. Step 1: Understand Docker's role

   Docker packages an app with all its dependencies and environment to ensure it runs the same everywhere.

2. Step 2: Identify deployment benefits

   This packaging helps avoid issues caused by different environments on different machines.

3. Final Answer:

   To package the app and its environment for consistent deployment -> Option C

4. Quick Check:

   Docker packages environment [OK]

Hint: Docker ensures app runs same everywhere by packaging environment [OK]

Common Mistakes:

• Thinking Docker speeds up coding
• Confusing Docker with Vue features
• Assuming Docker replaces Vue libraries

2. Which Dockerfile snippet correctly uses multi-stage build for a Vue app?

easy

A. FROM node:18 AS build
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
RUN npm run build
FROM nginx:alpine
COPY --from=build /app/dist /usr/share/nginx/html

B. FROM nginx:alpine
WORKDIR /app
COPY . .
RUN npm install
RUN npm run build

C. FROM node:18
WORKDIR /app
COPY . .
RUN npm run serve

D. FROM alpine
RUN apk add nodejs npm
COPY . .
RUN npm run build

Solution

1. Step 1: Identify multi-stage build pattern

   Multi-stage uses one stage to build (Node) and another to serve (Nginx).

2. Step 2: Check snippet correctness

   FROM node:18 AS build WORKDIR /app COPY package*.json ./ RUN npm install COPY . . RUN npm run build FROM nginx:alpine COPY --from=build /app/dist /usr/share/nginx/html builds with Node, then copies build output to Nginx image, which is correct.

3. Final Answer:

   Multi-stage build with Node for build and Nginx to serve -> Option A

4. Quick Check:

   Multi-stage build [OK]

Hint: Look for two FROM lines: build then serve [OK]

Common Mistakes:

• Using Nginx to build Vue app
• Not copying build output to Nginx
• Running npm serve inside Docker production image

3. Given this Dockerfile snippet, what will happen when you run the container?

FROM node:18 AS build
WORKDIR /app
COPY package.json .
RUN npm install
COPY . .
RUN npm run build
FROM nginx:alpine
COPY --from=build /app/dist /usr/share/nginx/html
EXPOSE 80
CMD ["nginx", "-g", "daemon off;"]

medium

A. The container will expose port 3000 instead of 80

B. The container will fail because npm run build is missing

C. The app will run Node server instead of Nginx

D. The Vue app will be built and served by Nginx on port 80

Solution

1. Step 1: Analyze build stage

   Node image installs dependencies and runs npm run build to create production files in /app/dist.

2. Step 2: Analyze serve stage

   Nginx image copies built files to its html folder and exposes port 80, running Nginx server.

3. Final Answer:

   The Vue app will be built and served by Nginx on port 80 -> Option D

4. Quick Check:

   Build then serve on port 80 [OK]

Hint: Build with Node, serve with Nginx on port 80 [OK]

Common Mistakes:

• Assuming npm run build is missing
• Confusing Node server with Nginx
• Wrong port exposed in container

4. You wrote this Dockerfile but your Vue app shows a blank page when running the container:

FROM node:18
WORKDIR /app
COPY . .
RUN npm install
RUN npm run build
FROM nginx:alpine
COPY dist /usr/share/nginx/html
EXPOSE 80
CMD ["nginx", "-g", "daemon off;"]

What is the likely error?

medium

A. Nginx image does not expose port 80

B. Missing multi-stage build alias causing wrong files copied

C. npm install command is incorrect

D. CMD syntax is invalid

Solution

1. Step 1: Check multi-stage build usage

   The Dockerfile lacks a build stage alias, so COPY dist copies from current stage, which is Nginx, not build output.

2. Step 2: Understand impact on app

   Because dist folder is not copied from build stage, Nginx serves empty or missing files, causing blank page.

3. Final Answer:

   Missing multi-stage build alias causing wrong files copied -> Option B

4. Quick Check:

   Missing build alias = blank page [OK]

Hint: Use --from=build to copy correct build files [OK]

Common Mistakes:

• Ignoring multi-stage build alias
• Assuming port exposure causes blank page
• Thinking npm install syntax is wrong

5. You want to optimize your Vue app Docker deployment by reducing image size and improving build speed. Which approach is best?

hard

A. Use a multi-stage Dockerfile with Node build stage and minimal Nginx serve stage

B. Install all dependencies in the Nginx image directly

C. Run npm run serve inside the Node image and expose port 8080

D. Copy source files directly to Nginx image and run npm build there

Solution

1. Step 1: Understand image size and build speed

   Multi-stage builds separate build environment from runtime, keeping final image small and clean.

2. Step 2: Evaluate options

   Use a multi-stage Dockerfile with Node build stage and minimal Nginx serve stage uses Node only for building, then copies only built files to lightweight Nginx image, optimizing size and speed.

3. Final Answer:

   Use a multi-stage Dockerfile with Node build stage and minimal Nginx serve stage -> Option A

4. Quick Check:

   Multi-stage build optimizes size and speed [OK]

Hint: Separate build and serve stages to keep image small [OK]

Common Mistakes:

• Installing dependencies in Nginx image
• Running dev server in production container
• Copying source files without building