Best practices

Default commands#

If you have many projects (lets say - microservices) - it would be great to have one way to run and operate them when developing

  • run command - the main purpouse of this command is to run all in once. If all projects has this command its easier to remember.
  • test command - each projects should have a tests and a way to run them, either one file or all tests at once
  • init command - some kind of project initialization - creates missing files, dirs for developer, checks permissions, login to docker registry, checks inotify limits for tools such as webpack and other file watchers.

Split lets.yaml when it becomes big.#

If lets.yaml became big, it may be great to split it in a smaller, more specific files using mixins directive. For example:

  • lets.yaml
  • lets.test.yaml
  • lets.build.yaml
  • lets.frontend.yaml
  • lets.i18n.yaml

In each of these files we then hold all specific tasks.

Use checskums#

Checksums can help you decrease amount of task executions. How ? Lets see.

Suppose we have js project and we obviously holding all dependencies in package.json. Also we are using Docker for reproducible development environment.

Dockerfile

FROM alpine:3.8
WORKDIR /work
COPY package.json .
RUN npm install
CMD ["npm start"]

What if we want to rebuild docker image every time we changed dependency ?

lets.yaml

shell: bash
commands:
run:
depends:
- build
cmd: docker-compose up application
build:
checksum:
- package.json
persist_checksum: true
cmd: |
if [[ ${LETS_CHECKSUM_CHANGED} == true ]]; then
docker-compose build application
else
Image is up to date
fi

As you can see, we execute build command each time we execute run command (depends).

persist_checksum will save calculated checksum to .lets directory and all subsequent calls of build command will read checksum from disk, calculate new checksum, and compare them. If package.json will change - we will rebuild the image.

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