In this blog post I will show how you can use a
Makefile to make your life easier.
In this blog I will use CDK with python. But the principle of the
Makefile will work on almost any project.
When you start a new PoC you do not have a full CI/CD environment in place yet.
So how can you deploy your CDK application? And make it easy to add the CI/CD pipeline at a later point?
I used CDK 1.124.0 (build 65761fe) for this blog post.
First we will need a CDK project. So we will create a working folder named:
mkdir makefile_cdk_blog cd makefile_cdk_blog cdk init --language python mkdir tests
At this point you will have an empty CDK project. Most projects have dependencies. You can divide them into 2 categories:
- Project dependencies, dependencies needed for the project, located in
- Development dependencies, dependencies needed to develop on the project, located in
Let’s start with adding some development dependencies in the
-e . black pytest pytest-cov pytest-black setuptools
Now we need to configure pytest. Add the following to a new file
[tool:pytest] testpaths = tests [coverage:run] branch = True source = makefile_cdk_blog [coverage:report] show_missing = true fail_under = 100 exclude_lines = pragma: no cover if __name__ == .__main__.:
The only thing left is the
Makefile itself. Create a file called
Makefile in the root of your project. Make sure it has the following content:
SHELL = /bin/bash -c VIRTUAL_ENV = $(PWD)/.venv export BASH_ENV=$(VIRTUAL_ENV)/bin/activate $(VIRTUAL_ENV): python3 -m venv $(VIRTUAL_ENV) .PHONY: install clean synth diff deploy test lint install: $(VIRTUAL_ENV) pip install -r requirements.txt clean: [[ -d $(VIRTUAL_ENV) ]] && rm -rf $(VIRTUAL_ENV) || true [[ -d .pytest_cache ]] && rm -rf .pytest_cache || true [[ -d cdk.out ]] && rm -rf cdk.out || true [[ -f .coverage ]] && rm .coverage || true synth: cdk synth diff: cdk diff deploy: test cdk deploy test: lint pytest --cov --cov-report term-missing lint: black . $(VERBOSE).SILENT:
Alright we are good to go! First we want to commit our changes, but before we can do that we should test them.
We added dependencies, so we need to install those first! But since we have a make target for that now we can use it.
I will walk you through what is happening on the background:
- First the
Makefilewill select bash as a shell.
- Define the location of the virtual environment.
BASH_ENVvariable has a dependency on the
$(VIRTUAL_ENV)target. It will create a virtual environment on the defined location.
- The virtual environment is then exported in the
- Then we will execute the
installtarget. All commands are now executed in the context of the virtual environment.
pip installwill install all dependencies in the
requirements.txtand in the
We can now run the
test target to see if everything works as expected.
You would see something like:
So what happened? We invoked the
test target. This target has a dependency on the
lint target contains
black . and this command formats all the python code. Afterwards, it will continue and execute the commands in the
So the test is failing because we did not meet the configured code coverage threshold. That is fine for now so let’s commit!
git add . git commit -m "chore: setup project using a Makefile"
Before we can deploy I assume that you configured your AWS credentials properly.
export AWS_PROFILE=my-profile-name make deploy
And it failed? Because the
deploy target has a dependency on the
test target. So the test target is being executed first but that fails.
This is the real power of using a
Makefile. You have simple names for actions that you want to do. For example: test, deploy, etc.
And in this case you should not deploy if your test fail.
You can extend these targets with different checks/commands.
For example, you could synthesize the template and then use the following tools:
Makefiles allow you to standardize actions across projects. They can execute commands in virtual environments for you. And if kept simple they are easy to read!