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Variable Substitutions

Variable substitutions are used to dynamically inject data and modify your configuration.

Usecases​

  • Database input parameters
  • Using environment variables or secrets
  • Dynamically building URLs or payload structures

How​

To substitute variables the following convention is followed a|<something>|.

  • All substitutions must start with a| and end with a |
  • You may notice in configs, input: a|body, input: a|params, input: a|headers these are not substitutions, they are for accessing data when used in the input parameter, as such they do not have a trailing |.
    • See Input Variables below on how to access values within the above mentioned.
  • Complicated substitutions such as templates, HTML, JSON etc. should use a literal scalar blocks eg.
actions:
    name: send data
    http:
        url: http://endpoint123.com/someroute
        body: | # <- literal scalar block
            a|var::some_big_json| # assuming a variable called `some_big_json` is stored in the global variable store

Input Variables​

To substitute a value from one of the above mentioned properties into a config it would need to be for eg. a|body::id|, a|params::id| this specifies a parameter to access, followed by a trailing | pipe.

Access a query parameter​

Access a query parameter
actions:
    name: doSomething
    http:
        url: http://endpoint123.com/someroute?id=a|params::id| 
        # ^^ access the value of `id` from the query parameters ^^

Access a value from the input body​

Access a value from the input body
actions:
    name: doSomething
    http:
        url: http://endpoint123.com/someroute?id=a|body::id| 
        # ^^ access the value of `id` from the input body ^^

Action Variables​

You can access data from prior actions with the following convention a|ACTION_NAME::some_variable|

We can access the firstname variable from the CheckBody action with a|CheckBody::firstname|, to supply as a parameter to our database query. This assumes that the input data for the CheckBody action contains a variable called firstname.

Access the variable named 'firstname' from the CheckBody action
    actions:
      - name: CheckBody
        input: a|body # <- NOT a variable substitution

      - name: CheckUser
        run_when_succeeded:
          - previous # wait for the previous action to complete
        database: main
        query: |
          SELECT firstname, lastname, address1 FROM customers WHERE firstname LIKE $1 LIMIT 2;
        params:
          - a|CheckBody::firstname| # <-- here

Global Variables​

See global variables.

Environment Variables (Self Hosted Only)​

Substitute an environment variable called MY_ENV into your configuration yaml with:
a|env::MY_ENV|

Substitute an environment variable called 'ORG_ID' into the url of the http request
   actions:
     - name: CheckBody
       http:
         url: https://some-endpoint.com/a|env::ORG_ID|/data/something