Customize your image on Astronomer Software

The Astro CLI is intended to make it easier to develop with Apache Airflow, whether you’re developing on your local machine or deploying code to Astronomer. The following guidelines describe a few of the methods you can use to customize the Docker Image that gets pushed to Airflow every time you rebuild your image locally using $ astro dev start or deploy to Astronomer using $ astro deploy.

More specifically, this doc includes instructions for how to:

• Add Python and OS-level packages
• Add dependencies
• Run commands on build
• Access the Airflow CLI
• Add environment variables locally
• Build from a private repository

Add Python and OS-level dependencies

To add Python packages to an Airflow Deployment, add the packages to the Deployment requirements.txt file. To add OS-level packages to an Airflow Deployment, add them to the Deployment packages.txt file. The requirements.txt and packages.txt files were automatically generated after running astro dev init to initialize your local Astro project.

Add Python dependencies

To add all Python packages to an Airflow Deployment, add the packages to the Deployment requirements.txt file.

To pin a version of that package, use the following syntax:

<package-name>==<version>

If you’d like to exclusively use Pymongo 3.7.2, for example, you’d add the following in your requirements.txt:

pymongo==3.7.2

If you do not pin a package to a version, the latest version of the package that’s publicly available will be installed by default.

Add OS-level dependencies

To add OS-level packages to an Airflow Deployment, add them to the Deployment packages.txt file.

Rebuild your image

Once you’ve saved those packages in your text editor or version control tool, rebuild your image by running:

astro dev stop

followed by

astro dev start

This process stops your running Docker containers and restarts them with your updated image.

Confirm your package was installed (Optional)

If you added pymongo to your requirements.txt file, for example, you can confirm that it was properly installed by running a $ docker exec command into your scheduler.

1. Run $ docker ps to identify the 3 running docker containers on your machine
2. Grab the container ID of your scheduler container
3. Run the following:

docker exec -it <scheduler-container-id> pip freeze | grep pymongo
pymongo==3.7.2

Add other dependencies

In the same way you can build Python and OS-level packages into your image, you’re free to build additional dependencies and files for your DAGs to use.

In the example below, we’ll add a folder of helper_functions with a file (or set of files) that our Airflow DAGs can then use.

Add the folder into your project directory

$
.
>
├── airflow_settings.yaml
>
├── dags
>
│   └── example-dag.py
>
├── Dockerfile
>
├── helper_functions
>
│   └── helper.py
>
├── include
>
├── packages.txt
>
├── plugins
>
│   └── example-plugin.py
>
└── requirements.txt

Rebuild your image

Follow the instructions in the “Rebuild your Image” section above.

Confirm your files were added (Optional)

Similar to the pymongo example above, you can confirm that helper.py was properly built into your image by running a $ docker exec command into your scheduler.

1. Run $ docker ps to identify the 3 running docker containers on your machine
2. Grab the container ID of your scheduler container
3. Run the following:

$
docker exec -it <scheduler-container-id> /bin/bash
>
bash-4.4$ ls
>
Dockerfile  airflow_settings.yaml  helper_functions  logs  plugins  unittests.cfg
>
airflow.cfg  dags  include  packages.txt  requirements.txt

Notice that helper_functions folder has been built into your image.

Configure airflow_settings.yaml

When you first initialize a new Astro project on Astronomer, a file titled airflow_settings.yaml will be automatically generated. With this file you can configure and programmatically generate Airflow connections, Pools, and Variables when you’re developing locally.

For security reasons, the airflow_settings.yaml file is currently only for local development and should not be used for pushing up code to Astronomer via $ astro deploy. For the same reason, we’d recommend adding this file to your .gitignore.

Add Airflow connections, pools, variables

By default, the airflow_settings.yaml file includes the following template:

1
airflow:
2
  connections: ## conn_id and conn_type are required
3
    - conn_id: my_new_connection
4
      conn_type: postgres
5
      conn_host: 123.0.0.4
6
      conn_schema: airflow
7
      conn_login: user
8
      conn_password: pw
9
      conn_port: 5432
10
      conn_extra:
11
  pools: ## pool_name, pool_slot, and pool_description are required
12
    - pool_name: my_new_pool
13
      pool_slot: 5
14
      pool_description:
15
  variables: ## variable_name and variable_value are required
16
    - variable_name: my_variable
17
      variable_value: my_value

Make sure to specify all required fields that correspond to the objects you create. If you don’t specify them, you will see a build error on $ astro dev start.

Additional entries

If you want to add a second Connection/Pool/Variable, copy the existing fields and make a new entry like so:

1
variables:
2
  - variable_name: my_first_variable
3
    variable_value: value123
4
  - variable_name: my_second_variable
5
    variable_value: value987

Run commands on build

If you’re interested in running any extra commands when your Airflow image builds, it can be added to your Dockerfile as a RUN command. These will run as the last step in the image build process.

For example, if you wanted to run ls when your image builds, your Dockerfile would look like this:

FROM quay.io/astronomer/astro-runtime-5.0.6
RUN ls

Docker Compose override

The Astro CLI is built on top of Docker Compose, a tool for defining and running multi-container Docker applications. To override the default CLI configurations, add a docker-compose.override.yml file to your Astro project directory. The values in this file override the default settings when you run $ astro dev start.

To add another volume mount for a directory named custom_dependencies, for example, add the following to your docker-compose.override.yml:

version: "3.1"
services:
  scheduler:
    volumes:
      - /home/astronomer_project/custom_dependencies:/usr/local/airflow/custom_dependencies:ro

Make sure to specify version: "3.1" and mimic the format of the source code file linked above.

When your image builds on $ astro dev start, any changes made within the custom_dependencies directory will be picked up automatically the same way they are with files in your dags directory:

$ docker exec -it astronomer_project239673_scheduler_1 ls -al
total 76
drwxr-xr-x    1 astro    astro         4096 Dec 30 17:21 .
drwxr-xr-x    1 root     root          4096 Dec 14  2018 ..
-rw-rw-r--    1 root     root            38 Oct  8 00:07 .dockerignore
-rw-rw-r--    1 root     root            31 Oct  8 00:07 .gitignore
-rw-rw-r--    1 root     root            50 Oct  8 00:10 Dockerfile
-rw-r--r--    1 astro    astro        20770 Dec 30 17:21 airflow.cfg
drwxrwxr-x    2 1000     1000          4096 Oct  8 00:07 dags
-rw-r--r--    1 root     root           153 Dec 30 17:21 docker-compose.override.yml
drwxrwxr-x    2 1000     1000          4096 Oct  8 00:07 include
drwxr-xr-x    4 astro    astro         4096 Oct  8 00:11 logs
drwxr-xr-x    2 1000     1000          4096 Dec 30 17:15 custom_dependencies
-rw-rw-r--    1 root     root             0 Oct  8 00:07 packages.txt
drwxrwxr-x    2 1000     1000          4096 Oct  8 00:07 plugins
-rw-rw-r--    1 root     root             0 Oct  8 00:07 requirements.txt
-rw-r--r--    1 astro    astro         2338 Dec 30 17:21 unittests.cfg

Access to the Airflow CLI

You’re free to use native Airflow CLI commands on Astronomer when developing locally by wrapping them around docker commands.

To add a connection, for example, you can run:

$
docker exec -it SCHEDULER_CONTAINER bash -c "airflow connections -a --conn_id test_three  --conn_type ' ' --conn_login etl --conn_password pw --conn_extra {"account":"blah"}"

Refer to the native Airflow CLI for a list of all commands.

Add environment variables locally

To import environment variables from a specific file, run $ astro dev start with an --env flag:

astro dev start --env .env

Install Python packages from private sources

Python packages can be installed from public and private locations into your image. To install public packages listed on PyPI, follow the steps in Add Python and OS-level Packages. To install packages listed on private PyPI indices or a private git-based repository, you need to complete additional configuration in your project.

Depending on where your private packages are stored, use one of the following setups to install your packages to an Astro project by customizing your Runtime image.

git+ssh://git@github.com/myorganization/mypackage1.git
git+ssh://git@github.com/myorganization/mypackage2.git
numpy==1.22.1

Add a CA certificate to an Astro Runtime image

If you need your Astro deployment to communicate securely with a remote service using a certificate signed by an untrusted or internal certificate authority (CA), you need to add the CA certificate to the trust store inside the image.

1. In your Astro project Dockerfile, add the following entry below the existing FROM statement which specifies your Astro Runtime image version:

   1
   USER root
   2
   COPY <path-for-internal-cert.crt> /usr/local/share/ca-certificates/<your-company-name>/
   3
   RUN update-ca-certificates
   4
   USER astro

2. Optional. Add additional COPY statements before the RUN update-ca-certificates stanza for each CA certificate your organization is using for external access.

3. Save your changes and test them locally, or deploy them to a test Deployment.