Time Saving Yaml Tricks

DRY: Don’t Repeat Yourself

If you have a section that’s being repeated multiple times, you can create an anchor and then reference it. You use &name to create an anchor, and then *name to reference it. One example of it is defining environment variables for different services in docker-compose.yaml.

env_vars: &env ENVIRONMENT: production LOGLEVEL: info AWS_REGION_NAME: us-east-1services: api: environment: *env ... ... backend: ... ... environment: *env

Reading environment variables

While yaml doesn’t read environment variables, but if you pair it with parser, you can read the environment variables. The syntax depends on the parser you are using. The most common places, where I have a need for reading environment variables (or context variables) in yaml file is, cicd pipeline namely github action or circleci and docker-compose.

# github action uses ${{ }}run: echo running with secrets $# circleci uses bash style syntax, you have to have these variables in circleci contextrun: echo running with secrets $MY_SECRET# docker-compose uses interpolation and will read MY_SECRET from your shell or .env fileenvironment: - MY_SECRET=${MY_SECRET}

Multiline strings

• Use > to convert line breaks into spaces. This will fold new lines into a single line until the line ends with a new line

description: > This is a long string that I want to break into multiple lines. But this will be second new line. # the above will actually be parsed like thisdescription: | This is a long string that I want to break into multiple lines But this will be second new line.

• Use | if you want to preserve structure, like line breaks and indentation, useful for writing code blocks.

run: | if [[ "$MY_ENV" == "test" ]]; then echo running in test environment fi