如何从另一个工作流程启动一个工作流程并检索被调用工作流程的返回值

我正在测试谷歌工作流程，并想从另一个工作流程调用工作流程，但作为一个单独的流程（不是子工作流程）

我可以开始执行，但目前无法检索返回值。我收到了一个执行实例：

{
     "argument": "null",
     "name": "projects/xxxxxxxxxxxx/locations/us-central1/workflows/child-workflow/executions/9fb4aa01-2585-42e7-a79f-cfb4b57b22d4",
     "startTime": "2020-12-09T01:38:07.073406981Z",
     "state": "ACTIVE",
     "workflowRevisionId": "000003-cf3"
 }

父工作流.yaml

main:
params: [args]

steps:
    
    - callChild:
        call: http.post
        args:
            url: 'https://workflowexecutions.googleapis.com/v1beta/projects/my-project/locations/us-central1/workflows/child-workflow/executions'
            auth: 
                type: OAuth2
                scope: 'https://www.googleapis.com/auth/cloud-platform'
        result: callresult
    
    - returnValue:
        return: ${callresult.body}

子工作流.yaml：

 - getCurrentTime:
        call: http.get
        args:
            url: https://us-central1-workflowsample.cloudfunctions.net/datetime
        result: CurrentDateTime
    - readWikipedia:
        call: http.get
        args:
            url: https://en.wikipedia.org/w/api.php
            query:
                action: opensearch
                search: ${CurrentDateTime.body.dayOfTheWeek}
        result: WikiResult
    - returnOutput:
        return: ${WikiResult.body[1]}

另外还有一个问题：如何从变量创建动态 url。 ${} 似乎在那里不起作用

由于执行是异步 API 调用，因此您需要对工作流程进行轮询以查看何时完成。

你可以有以下算法：

main:
  steps:  
    - callChild:
        call: http.post
        args:
            url: ${"https://workflowexecutions.googleapis.com/v1beta/projects/"+sys.get_env("GOOGLE_CLOUD_PROJECT_ID")+"/locations/us-central1/workflows/http_bitly_secrets/executions"}
            auth: 
                type: OAuth2
                scope: 'https://www.googleapis.com/auth/cloud-platform'
        result: workflow
    - waitExecution:
        call: CloudWorkflowsWaitExecution
        args:
          execution: ${workflow.body.name}
        result: workflow
    - returnValue:
        return: ${workflow}
CloudWorkflowsWaitExecution:
  params: [execution]
  steps:
    - init:
        assign:
          - i: 0
          - valid_states: ["ACTIVE","STATE_UNSPECIFIED"]
          - result: 
              state: ACTIVE
    - check_condition:
        switch:
          - condition: ${result.state in valid_states AND i<100}
            next: iterate
        next: exit_loop
    - iterate:
        steps:
          - sleep:
              call: sys.sleep
              args:
                seconds: 10
          - process_item:
              call: http.get
              args:
                url: ${"https://workflowexecutions.googleapis.com/v1beta/"+execution}
                auth:
                  type: OAuth2
              result: result
          - assign_loop:
              assign:
                - i: ${i+1}
                - result: ${result.body} 
        next: check_condition
    - exit_loop:
        return: ${result}

你在这里看到的是我们有一个CloudWorkflowsWaitExecution子工作流最多循环100次，也有10秒的延迟，当工作流完成时会停止，并返回结果。

输出是：

argument: 'null'
endTime: '2020-12-09T13:00:11.099830035Z'
name: projects/985596417983/locations/us-central1/workflows/call_another_workflow/executions/05eeefb5-60bb-4b20-84bd-29f6338fa66b
result: '{"argument":"null","endTime":"2020-12-09T13:00:00.976951808Z","name":"projects/985596417983/locations/us-central1/workflows/http_bitly_secrets/executions/2f4b749c-4283-4c6b-b5c6-e04bbcd57230","result":"{\"archived\":false,\"created_at\":\"2020-10-17T11:12:31+0000\",\"custom_bitlinks\":[],\"deeplinks\":[],\"id\":\"j.mp/2SZaSQK\",\"link\":\"//<edited>/2SZaSQK\",\"long_url\":\"https://cloud.google.com/blog\",\"references\":{\"group\":\"https://api-ssl.bitly.com/v4/groups/Bg7eeADYBa9\"},\"tags\":[]}","startTime":"2020-12-09T13:00:00.577579042Z","state":"SUCCEEDED","workflowRevisionId":"000001-478"}'
startTime: '2020-12-09T13:00:00.353800247Z'
state: SUCCEEDED
workflowRevisionId: 000012-cb8

in the result有一个子项保存外部工作流程执行的结果。