Why container registry matters in GCP - Why It Works

Introduction

A container registry stores your app containers safely so you can use them anytime. It solves the problem of sharing and managing container images easily across different computers or cloud services.

When you want to save your app container so your team can use it later.

When you need to deploy your app container to Google Cloud services like Cloud Run or Kubernetes Engine.

When you want to keep different versions of your app container organized and easy to find.

When you want to share your app container securely with other developers or systems.

When you want to automate app updates by pulling the latest container from a trusted place.

Commands

This command sets up your local Docker to connect securely to Google Container Registry so you can push and pull containers.

Terminal

gcloud auth configure-docker

Expected Output

Docker configuration file updated to use gcloud as a credential helper.

This builds your app container locally and tags it with the Google Container Registry path and version.

Terminal

docker build -t gcr.io/my-project/my-app:v1 .

Expected Output

Sending build context to Docker daemon  10.24kB

Step 1/5 : FROM python:3.10-slim

 ---> 123abc456def

Step 2/5 : COPY . /app

 ---> Using cache

Step 3/5 : WORKDIR /app

 ---> Using cache

Step 4/5 : RUN pip install -r requirements.txt

 ---> Using cache

Step 5/5 : CMD ["python", "app.py"]

 ---> Using cache

Successfully built abcdef123456

Successfully tagged gcr.io/my-project/my-app:v1

→

-t - Tags the image with a name and version for the registry

This uploads your tagged container image to Google Container Registry so it can be used by cloud services.

Terminal

docker push gcr.io/my-project/my-app:v1

Expected Output

The push refers to repository [gcr.io/my-project/my-app]

abcdef123456: Pushed

v1: digest: sha256:abcdef1234567890 size: 1234

This lists all versions of your app container stored in Google Container Registry.

Terminal

gcloud container images list-tags gcr.io/my-project/my-app

Expected Output

DIGEST                                                                    TAGS     TIMESTAMP

sha256:abcdef1234567890                                                   v1       2024-06-01T12:00:00

sha256:123456abcdef7890                                                   v2       2024-06-02T15:30:00

Key Concept

If you remember nothing else from this pattern, remember: a container registry safely stores and shares your app containers so they can be used anywhere.

Common Mistakes

Trying to push a container image without authenticating Docker to Google Container Registry.

Docker will reject the push because it does not have permission to upload images.

Run 'gcloud auth configure-docker' first to set up authentication.

Tagging the container image with a wrong or incomplete registry path.

Docker push will fail because it cannot find the correct destination in the registry.

Always tag images with the full registry path like 'gcr.io/my-project/my-app:tag'.

Not checking the list of images in the registry after pushing.

You might think the push failed or be unaware of the available versions.

Use 'gcloud container images list-tags' to verify your images are stored.

Summary

Authenticate Docker to Google Container Registry using 'gcloud auth configure-docker'.

Build your container image locally and tag it with the full registry path.

Push the tagged image to Google Container Registry for storage and sharing.

List stored images to verify your container versions are available.