Introduction > Step Functions > Step Function调用Lambda

Step Function调用Lambda

本节我们将使用Step Function实现以下工作流：

传入一个Purchase Type事件，当它为PURCHASE时，调用purchase lambda处理；如果是REFUND，则调用refund lambda处理。

创建两个lambda

进入Lambda页面，创建purchase_function函数：

代码更新如下，并进行部署：

import json
import datetime

def lambda_handler(message, context):
    print(message)

    response = {}
    response['TransactionType']=message['TransactionType']
    response["TimeStamp"] = datetime.datetime.now().strftime("%Y-%m-%d %H-%M-%S")
    response["Message"] = "Hello from lambda land inside the ProcessPurchase function!"
    return response

再创建refund_function:

更新代码如下，进行部署：

import json
import datetime

def lambda_handler(message, context):
    print(message)

    response = {}
    response['TransactionType']=message['TransactionType']
    response["TimeStamp"] = datetime.datetime.now().strftime("%Y-%m-%d %H-%M-%S")
    response["Message"] = "Hello from lambda land inside the RefundPruchase function!"
    return response

将上面创建的两个Lambda的ARN复制下来，后面会使用到：

形如以下格式：

arn:aws:lambda:us-east-1:145197526627:function:refund_function
arn:aws:lambda:us-east-1:145197526627:function:purchase_function

创建Step Functions

进入Step Functions服务，点击Create state machine:

这里我们选择Write your workflow in code:

Step Functions的JSON定义如下，将两处Resource替换为上一步获取到的Lambda ARN：

{
  "Comment": "Transaction Process State Machine",
  "StartAt": "ProcessTransaction",
  "States": {
    "ProcessTransaction": {
      "Type": "Choice",
      "Choices": [
        {
          "Variable": "$.TransactionType",
          "StringEquals": "PURCHASE",
          "Next": "ProcessPurchase"
        },
        {
          "Variable": "$.TransactionType",
          "StringEquals": "REFUND",
          "Next": "ProcessRefund"
        }
      ]
    },
    "ProcessRefund": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:us-east-1:145197526627:function:refund_function",
      "End": true
    },
    "ProcessPurchase": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:us-east-1:145197526627:function:purchase_function",
      "End": true
    }
  }
}