What are AWS Step Functions?

Step Functions are a visual workflow service offered by AWS. It has a drag-and-drop visual console that helps the users create workflows of business-critical processes. It is mainly used in helping organizations to blend more than one AWS service while allowing them to also manage each of the microservices separately.

Features of Step Functions

1. State Machine

A state machine is a basic idea that symbolizes a workflow in AWS Step Functions. It is mainly composed of several states joined together by transitions. Each state carries out a particular action or task, such as calling a Lambda function, picking a course of action, anticipating an event, or running multiple tasks simultaneously. State machines make it simple to manage, define, and monitor complex applications by giving a visual representation of the workflow. A state machine enables the creation of scalable and resilient applications by enabling the coordination and serverless orchestration of various AWS services.

2. State

Step Functions provide different types of states, each serving a specific purpose:

Task State: Representing the execution of a specific task or action, a Task state serves as the primary means to run custom code or interact with external systems within a workflow. It can perform a range of functions, such as invoking an AWS Lambda function, executing activities in Amazon Simple Workflow Service, running an AWS Batch job, or interacting with AWS services.

Choice State: One or more conditions based on input data are evaluated in a Choice state. This allows for branching and decision-making within the workflow. Depending on the evaluated conditions, the workflow execution is directed to different paths or states.

Pass State: Performing any substantial work is not a task of a Pass state. Instead, it simply passes its input data to its output data. This state is often utilized to modify or transform the data between states. For example, it can extract specific values or change data structures.

Wait State: Before moving to the next state, a Wait state is implemented to introduce a timed delay or wait for a specific event or condition. This delay or pause in workflow execution allows for the introduction of a timed delay or the waiting for a specific event or condition.

Parallel State: A Parallel state allows multiple branches of states to be executed concurrently. This means that different paths of execution can happen at the same time, enabling parallel processing or simultaneous actions.

Fail State: An error or failure is indicated by a Fail state, which represents a terminal state in the workflow. This state occurs when the workflow execution encounters an error or failure. Information about the failure is provided in the form of an error message or cause.

Within a given workflow, AWS Step Functions employ states to encapsulate distinct actions, decisions, or behaviors. This permits the definition of the workflow’s flow and logic, empowering the construction of intricate and coordinated systems through the interconnection of various states. Within this system, each state processes its specific input data, generating output data that can then be transmitted to succeeding states. Consequently, a sequence of interconnected actions is formed, effectively representing the flow of execution within the workflow.

3. Transition

Defining the flow and progression of workflows in a state machine relies heavily on transitions within Step functions. We can say that these transitions determine the movement between states based on specific conditions or events.

Describing rules or conditions, transitions explain the evaluation of the output of a state and determine the next state to transition to. The evaluation of these conditions considers factors like a combination of input or output data of the state and enables the workflow execution to progress to a different state.

Transitions are established by evaluating the conditions specified in the state definition in a Choice state, for example. Each condition is associated with a potential next state, and the transition occurs to the state where the condition evaluates to true.

We can build resilient and adaptable workflows in AWS Step Functions using transitions that control execution flow based on earlier state results. Dynamic and flexible workflows that implement branching, decision-making, looping, and error handling are enabled by transitions.

4. Tasks

Tasks in AWS Step Functions are the units of work performed within a state machine. You can execute them in a Task state, one of the available state types in Step Functions. With tasks, you can invoke AWS Lambda functions, interact with different AWS services, execute activities in Amazon Simple Workflow Service (SWF), or run AWS Batch jobs.

Before moving on to the next state, the state machine will call the specified task and wait for it to finish. This task can be either an AWS Lambda function or an activity in SWF, and its ARN (Amazon Resource Name) must be specified when defining the Task state.

AWS step functions process that calls the AddNumbers service, First, we will add input numbers, and then it will be decided whether the output number is greater than or less than the given constraints and the final state will be decided upon the results. While we could have one Lambda function call the other, we worry that managing all of those connections will become challenging as the AddNumbers application becomes more sophisticated. Plus, any change in the flow of the application will require changes in multiple places, and we could end up writing the same code over and over again.