CloudFlow:Overview

Basics

FDL is used to describe and define business logic. When a flow is executed, the Serverless workflow service executes steps in sequence based on the flow definition. In FDL, a flow usually contains several steps. These steps can be simple atomic steps, such as task, succeed, fail, wait, and pass steps, or complex control steps, such as choice, parallel, and foreach steps. These steps can be combined to build complex business logic. For example, a branch of a parallel step may be a series of serial steps. Errors may occur in the execution of steps, but FDL provides the retry and catch capabilities.

Steps in FDL are similar to functions in programming languages, and a combination of steps is similar to function calls. Data is passed between steps through input and output. Local variables are used to store data of steps. If a step contains another step, the outer step is called a parent step, and the included step is called a child step.

A flow contains the following attributes:

• version: Required. The flow version. Only v1 is supported.
• type: Required. The flow type.
• steps: Required. Multiple serial steps in a flow. When a step is executed successfully, the next step starts. To stop a flow in advance, you can use the end attribute or execute a succeed or fail step.
• inputMappings: Optional. The input mappings. The $input referenced in the input mappings is the Input parameter in a StartExecution API request.
• outputMappings: Optional. The output mappings. The $local referenced in the output mappings is a JSON object that records the execution result of each serial step.
  Note If no output mappings are specified, $local is used as the final flow output.
• timeoutSeconds: Optional. The timeout period of a flow. If the flow execution duration exceeds the specified timeout period, the flow times out.

Examples

• The following sample flow consists of a task step that calls a function of Function Compute:

  version: v1
  type: flow
  steps:
    - type: task
      name: hello
      resourceArn: acs:fc:{region}:{accountID}:services/fnf_test/functions/hello      

• The following sample flow consists of two steps (step1 and step4), in which step1 contains two child steps (step2 and step3).

  version: v1
  type: flow
  steps:
    - type: parallel
      name: step1
      branches:
        - steps:
          - type: pass
            name: step2
        - steps:
          - type: pass
            name: step3
    - type: pass
      name: step4       

References

For more information about FDL features, see the following topics:

• Inputs and outputs
• Task steps
• Wait steps
• Pass steps
• Choice steps
• Parallel steps
• Foreach steps
• Succeed steps
• Fail steps