Custom Flows

You can create custom flows for a template, that allow you to run whatever you want (bash, python, gcloud, ansible, cloudformation, etc.), whenever you want in the deployment process (before or after Terraform init/plan/apply, and even destroy/error).
Create a file named env0.yml to define a custom flow. env0 will use this file it is defined.

Below is an example of a custom flow which creates a more "dynamic" Terraform file, based on an environment variable value, and uses Python and Jinja before the Terraform Init (the full example of this template git repo (including the env0.yml file) is here):

version: 1

deploy:
  steps:
    terraformInit:
      before:
        - pip install --user j2cli
        - 'echo Generating "stage.auto.tfvars" for "$STAGE"'
        - j2 stage.auto.tfvars.j2 > stage.auto.tfvars
        - 'echo -e "Generated \"stage.auto.tfvars\": \n$(cat stage.auto.tfvars)"'
        - 'echo Generating "elb.tf" for "$STAGE"'
        - j2 elb.tf.j2 > elb.tf
        - 'echo -e "Generated \"elb.tf\": \n$(cat elb.tf)"'

You can include the following possible hooks in an env0.yml file:

version:
  type: number
​
deploy:
  onCompletion:
    - type: string
  onSuccess:
    - type: string
  onFailure:
    - type: string
​
  steps:
    setupVariables:
      after:
        - type: string
​
    terraformInit:
      before:
        - type: string
      after:
        - type: string
​
    terraformPlan:
      before:
        - type: string
      after:
        - type: string
​
    terraformApply:
      before:
        - type: string
      after:
        - type: string
​
    storeState:
      before:
        - type: string
      after:
        - type: string
​
    terraformOutput:
      before:
        - type: string
      after:
        - type: string
​
destroy:
  onCompletion:
    - type: string
  onSuccess:
    - type: string
  onFailure:
    - type: string
​
  steps:
    setupVariables:
      after:
        - type: string
​
    terraformInit:
      before:
        - type: string
      after:
        - type: string
​
    terraformPlan:
      before:
        - type: string
      after:
        - type: string
​
    terraformDestroy:
      before:
        - type: string
      after:
        - type: string

Handling errors

If any command in your custom flow returns a non-zero exit code, the env0 deployment will stop on a 'Failed' status. You can leverage this to perform validation - for example - asserting a certain environment variable was supplied.
In such a case, env0 will display any output from stderr as the deployment error. If no output is found in stderr, it will be shown as an "Unknown Error".

Here is an example -

version:
  type: 1
deploy:
  steps:
    setupVariables:
      after:
        - if [ -z "$MY_VAR" ]; then echo "MY_VAR must be supplied" 1>&2 && exit 1; fi

Exposed env0 System Environment Variables

env0 exposes the following environment variables for you to use:

See this sample of using these variables in our public templates repo.

The Deployment Container

Our deployment container is based on node:12-alpine and includes the following:

📘

Note

You can bring your own docker image, extending env0's default image (which is based on node:12-alpine), in case you are using our Self-Hosted Agent.

In order to learn more about custom docker images, please contact our support team.

Adding additional binaries to the container on the fly

You can easily download any binary needed using the curl command in all steps. You can also place that new binary under opt folder in case you need it within your PATH.