Iteration

for_each

You can run a step in a parallel loop using for_each:

Note that for_each accepts a map or a list of strings:

When using the list form, each.key will be the index of the current item in the list, and each.value is the actual list item.

You may need to reference an "iterated" step in an output or another step. These step instances are identified by a map key (or set member) from the value provided to for_each:

• step.<TYPE>.<NAME> (e.g.step.http.add_a_user) refers to the block. Note that depends_on will use the block reference, and that the dependency means all instances of the step. You cannot depend on a specific instance of a step from a for_each loop.
• step.<TYPE>.<NAME>[<KEY>] (e.g.step.http.add_a_user["0"], step.http.send_to_slack["AKIAXYSEVFAKE0123456"]) refers to an individual step instance.

For example, to wait until all the add_a_user steps have completed before sending a notification:

The step instances for a for_each are represented by a map, you can chain steps together where there is a 1:1 relationship between them (see Terraform resource chaining). For instance, we can modify the previous example to send a separate notification for each user:

In fact, you can use for_each and if in the same step (for_each is evaluated before if), so you could improve the example:

loop

You can also run a step in a sequential loop, changing the arguments with each iteration. This is useful for handling HTTP pagination, for example. To iterate the step, include a loop block. The until condition is used to break the loop - Flowpipe will run the step again unless the until condition is true. Once the until condition is true the loop is broken, the step completes, and execution continues at the next step.

The loop is evaluated last after the step instance has been executed and all retries have been completed. You can use the special value result to evaluate the attributes of the completed step instance (you can use result in an error handling block like throw, error, and retry as well). result is essentially a self-reference to "this" step after it has run (e.g. the attributes are populated).

When the step runs again due to the loop, it inherits all of the arguments from the step, but you can override them inside the loop block if desired, allowing you to pass data from the step execution into the next step execution. For instance, you may extract a pagination token from an HTTP response, and then override the step's url argument and pass that token in as a querystring parameter:

There is a special attribute called loop with a single attribute index which is the (zero-based) index of the loop count: