Custom Flows

You can create custom flows for a template, that allows 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).

For specific custom flow per template:
Create a file named env0.yml under the template folder. env0 will use this file when is defined.

For sharing custom flow for all templates:
Create a file named env0.yml under the root folder. env0 will use this file when it is defined and the template folder doesn't define this file.

For sharing custom flow for all environments under the project:
Create a custom flow file in any repository and configure it as a project policy.

We support the suffixes env0.yml and env0.yaml in the same way.

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Working Directory for env0.yml

env0 will run custom flow commands with a working directory based on where the file was taken.
Based on that you can reference your commands to other scripts/commands by using "./script.sh"

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.

Terraform

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

Pulumi

version:
  type: number

deploy:
  onCompletion:
    - type: string
  onSuccess:
    - type: string
  onFailure:
    - type: string

  steps:
    setupVariables:
      after:
        - type: string

    pulumiPreview:
      before:
        - type: string
      after:
        - type: string

    pulumiUp:
      before:
        - type: string
      after:
        - type: string

    storeState:
      before:
        - type: string
      after:
        - type: string

    pulumiOutput:
      before:
        - type: string
      after:
        - type: string

destroy:
  onCompletion:
    - type: string
  onSuccess:
    - type: string
  onFailure:
    - type: string

  steps:
    setupVariables:
      after:
        - type: string

    pulumiPreview:
      before:
        - type: string
      after:
        - type: string

    pulumiDestroy:
      before:
        - type: string
      after:
        - type: string

Kubernetes

version:
  type: number

deploy:
  onCompletion:
    - type: string
  onSuccess:
    - type: string
  onFailure:
    - type: string

  steps:
    setupVariables:
      after:
        - type: string
    
    k8sDiff:
      before:
        - type: string
      after:
        - type: string

    k8sApply:
      before:
        - type: string
      after:
        - type: string

    storeState:
      before:
        - type: string
      after:
        - type: string

destroy:
  onCompletion:
    - type: string
  onSuccess:
    - type: string
  onFailure:
    - type: string

  steps:
    setupVariables:
      after:
        - type: string

    k8sDiff:
      before:
        - type: string
      after:
        - type: string

    k8sDelete:
      before:
        - type: string
      after:
        - type: string

CloudFormation

version:
  type: number

deploy:
  onCompletion:
    - type: string
  onSuccess:
    - type: string
  onFailure:
    - type: string

  steps:
    setupVariables:
      after:
        - type: string

    cfCreateChangeSet:
      before:
        - type: string
      after:
        - type: string

    cfDeploy:
      before:
        - type: string
      after:
        - type: string

    cfOutput:
      before:
        - type: string
      after:
        - type: string

    storeState:
      before:
        - type: string
      after:
        - type: string

destroy:
  onCompletion:
    - type: string
  onSuccess:
    - type: string
  onFailure:
    - type: string

  steps:
    setupVariables:
      after:
        - type: string

    cfListStackResources:
      before:
        - type: string
      after:
        - type: string

    cfDeleteStack:
      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".

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Error Message Handling

Use the following notation 1>&2 to redirect stdout messages to stderr. This allows env0 to display the message in its UI. (see I/O Redirection)

Here is an example -

version: 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 for using these variables in our public templates repo.

The Deployment Container

Our deployment container is based on node:16.10.0-alpine3.16 and includes the following:

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Note

You can bring your own docker image, extending env0's default image (which is based on node:16.10.0-alpine3.11), 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. Additionality, Using apk add, pip install and npm install commands are accessible via sudo.

Exporting your own environment variables

In order to export your own Environment Variable to use in any downstream custom flow you should write a shell command in the format: echo KEY=VALUE >> $ENV0_ENV.
In later steps of the same deployment, you will be able to use $KEY to access the stored value.

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Note

For env0.yml files that use schema version 2 when using multiple commands within a given step e.g. "terraform:plan-before", all commands are executed inside the same shell. Exported environment variables as such are only available for steps that will come after the step. For using the values within the same shell using the usual export key=value still works.

Forcing Manual Approvals

Whenever ENV0_REQUIRES_APPROVAL=true env0 will force a deployment to be approved regardless of the "Auto Approval" setting in the environment. For example, instead of failing a deployment based on some policies, we can use this field to help ensure that someone can still review and proceed with the deployment.

Usage:
- echo ENV0_REQUIRES_APPROVAL=true >> $ENV0_ENV

FAQ

Q. How can I use Custom Flows to add new Terraform Variables?
The recommended approach to adding terraform variables is to use variable definitions files, specifically the _.auto.tfvars or _.auto.tfvars.json files to pass additional variables to your Terraform code. Note: Please be aware of the Terraform Variable Definition Precedence order as defined here: https://www.terraform.io/docs/language/values/variables.html#variable-definition-precedence.
Another way is to create new Environment Variables inside the custom flow in the form TF_VAR_key=value. To do that please follow Exporting your own environment variables.

Q. I noticed that env0 runs Init again after an approval, how can I only run my custom flow once per deployment?
You can take advantage of the ENV0_REVIEWER_NAME field to see if the plan has already been approved.
e.g.

deploy:
  steps:
    terraformInit:
      before: # run ./myScript.sh only on pre-approval
        - if [[ -z $ENV0_REVIEWER_NAME ]]; then ./myScript.sh; fi  

Q. Does env0 SaaS runners use static IP addresses? I would like to whitelist env0's runners to access my network.
Yes, env0's public IPs are:
18.214.210.123
44.195.170.230

You can also use our TF Provider to fetch the IP addresses dynamically.

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GitHub API limits

When downloading resources from GitHub (e.g. tflint) make sure you use an authenticated call (e.g. curl -u USER:TOKEN). Otherwise, you will likely run into API limits, as unauthenticated calls are pooled with other SaaS users, with a much lower API limit. See GitHub Rate Limiting.

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Additional Content

• Managing Terraform variable hierarchy
• Why env0 is a Terraform Cloud alternative?