how-to-write-dockerfile's Introduction

Dockerfile

Stage 1 uses node:lts-alpine as its base and uses builder as the stage name.
On line 5, we install python, make, and g++. The node-gyp tool requries these three packages to run.
On line 7, we set /app directory as the WORKDIR.
On line 9 and 10, we copy the package.json file to the WORKDIR and install dependencies
Stage 2 also uses node-lts:alpine as the base.
On line 16, we set the NODE_ENV environment variable to production. This is important for the API to run properly.
From line 18 to line 20, we set the default user to node, create the /home/node/app directory, and set that as the WORKDIR.
On line 22, we copy all the project files and on line 23 we copy the node_modules directory from the builder stage. This directory contains all the built dependencies necessary for running the application.
On line 25, we set the default command.

Attach volume and network bridge

Once notes-db container is running, uses the notes-db-data volume, and is attached to the notes-api-network bridge.

docker container run \
  --detach \
  --name=notes-api \
  --env DB_HOST=notes-db \
  --env DB_DATABASE=notesdb \
  --env DB_PASSWORD=secret \
  --publish=3000:3000 \
  --network=notes-api-network \
  notes-api

The notes-api application requires three environment variables to be set.

DB_HOST - This is the host of the database server. Given that both the database server and the API are attached to the same user-defined bridge network, the database server can be referred to using its container name which is notes-db in this case.
DB_DATABASE - The database that is API will use. On Running the database server we set the default database name to notesdb using the POSTGRES_DB environment variable. We'll use that here.
DB_PASSWORD - Password for connecting to the database. This was also set on running the database server sub-section using the POSTGRES_PASSWORD environment variable.

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