Step Functions

• Step Functions coordinate multiple AWS services into serverless workflows using State Machines.

• A state machine is an abstract model which decides how one state moves to another based on a series of conditions.

• Think of a state machine like a flow chart.

• Step Functions automatically triggers and tracks each step, and retries when there are errors, so your application executes in order and as expected, every time

• Amazon States Language is how you define all your states and is written in JSON.

• There are two types of State Machines available:

• Standard - general purpose, long workloads

• Express - streaming data, short workloads

• Use Cases for Step Functions:

• Manage a batch job, Fargate or ECS container

• Sequential batch processing

• Creating a pipeline to transcode media files

• Transferring data records, by performing operations on each record queued up via SQS

• Sequence steps of ML workflows

• Coordinate Extract, Transform and Load (ETL) Jobs

• The type of Step Functions States

  • Pass State Passes its input to its output, without performing work (dummy/mock). Pass states are useful when constructing and debugging state machines.
  • Task State represents a single unit of work performed by a state machine.
    • Lambda - triggers a lambda function
    • Activity the work is performed by a worker that can be hosted on anywhere eg. EC2, ECS, mobile phones
  • Supported AWS Services pass parameters to the APl of an AWS Service
  • Choices State adds branching logic to a state machine.
  • Wait State delays the state machine from continuing for a specified time.
  • Succeed State stops an execution successfully
  • Fail State stops the execution of the state machine and marks it as a failure
  • Parallel State can be used to create parallel branches of execution in your state machine The state machine doe not move forward until both states complete
  • Map State can be used to run a set of steps for each element of an input array.