Docker compose with Multi stage : why create same images?

Question

I deploying Vue app, and use method multi-stage ( with Nginx as server ) . Structure files :

docker-compose.yml
client ( folder code )
- Dockerfile

This is files config :

docker-compose.yml

version: '3.4'

services:
  client:
    build:./client
    ports:
      - "8080:80"
    volumes:
      - "./client:/app"
      - "/app/node_modules"

Dockerfile

FROM node:lts-alpine as build-stage
WORKDIR /app
COPY package*.json ./
RUN npm install
COPY . .
RUN npm run build

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

This run so smooth. But, when i changed content of source code and rebuild image with

docker-compose build client

docker-compose up --build

( or some arguments --no-cache, --force-recreate ... event set name for it )

It always will create new 2 image : 23.6MB and 333MB as below

docker images
REPOSITORY   TAG           IMAGE ID       CREATED          SIZE
root_ad      latest        236945fbfbb5   7 minutes ago    23.6MB
<none>       <none>        fbdc81e7983c   7 minutes ago    333MB
<none>       <none>        7969e4ba9ecf   18 minutes ago   23.6MB
<none>       <none>        e31655da8c88   18 minutes ago   333MB
<none>       <none>        4d5cae08a889   20 minutes ago   23.6MB
<none>       <none>        ee369d2602a9   20 minutes ago   333MB
nginx        alpine        513f9a9d8748   3 weeks ago      22.9MB
node         15.0-alpine   1e8b781248bb   11 months ago    115MB

How can i rebuild image without duplicate its ?

score 0 · Answer 1 · answered Oct 04 '21 at 04:01

0

when your using docker-compose, you don't need to build the container separately,

just run,

docker-compose up --build

because in your docker-compose.yml file you're already specified to build the image using client Dockerfile, build:./client.

then it will not create the same image again and again

answered Oct 04 '21 at 04:01

S.Sachith

536
1
9
21

1

I tried, same . Maybe, problem only appeare with multi stage – Mòe Oct 04 '21 at 04:09

rzlvmp · Accepted Answer · 2021-10-04T13:53:58.340

23.6MB's none is production-stage
333MB's none is build-stage

That is intermediate temporary images. You may delete it.

Why that appear again and again?

Even if first part:

FROM node:lts-alpine as build-stage
WORKDIR /app
COPY package*.json ./
RUN npm install

is always the same (Let's say we don't changing package*.json)

The second part:

COPY . .
RUN npm run build

Always changing because you copying updated source code at every build.

Docker needs to create every time new intermediate image to be able run

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

from this intermediate build-stage image

After that docker creates new image production-stage (as none) and tags it as root_ad:latest.

Why here is three 23.6MB's images and only one is root_ad:latest?

Because at every build docker untag older root_ad:latest and add this tag to newer 23.6MB's none.

You may check this behaviour by edit manually image version at every build:

version: '3.4'

services:
  client:
    build:./client
    image: root_ad:version_1 # add version manually here
    ...

After that you will see something like:

docker images
REPOSITORY   TAG           IMAGE ID       CREATED          SIZE
root_ad      version_3     236945fbfbb5   7 minutes ago    23.6MB
<none>       <none>        fbdc81e7983c   7 minutes ago    333MB
root_ad      version_2     7969e4ba9ecf   18 minutes ago   23.6MB
<none>       <none>        e31655da8c88   18 minutes ago   333MB
root_ad      version_1     4d5cae08a889   20 minutes ago   23.6MB
<none>       <none>        ee369d2602a9   20 minutes ago   333MB
nginx        alpine        513f9a9d8748   3 weeks ago      22.9MB
node         15.0-alpine   1e8b781248bb   11 months ago    115MB

It's also important to realize that deleting a 23.6MB image won't necessarily save 23.6MB of disk space. It'll clean up the images list (which is good), but two things will occur. First, if two similar images are obtained from the same initial build steps (say, about 20MB of data) and the last build step differs (say 3.6MB), the common 20MB was only stored once on the disk, so only 3.6MB will be deleted when you delete the image. Second, I'm not certain if this is true for multistage builds, but for simple builds, the 333MB image will also be stored as the base 23.6MB plus the 310MB "diff". — NicolasB, Oct 04 '21 at 10:39

Docker compose with Multi stage : why create same images?

2 Answers2