workflows-awaits-sheets-callback

Workflows that pause and wait for human approvals from Google Sheets

In this sample, we show you how to have a workflow wait for human approval from Google Sheets.

More specifically:

1. A workflow runs some initial steps.
2. The workflow creates a callback, saves the callback info to a Google Sheets spreadsheet, and starts to wait for an approval from a human for the rest of the steps.
3. A human sends his/her approval via the Google Sheets spreadsheet.
4. The workflow receives the approval and runs the rest of the steps.

Create a Google Sheet

First, create a Google Sheet spreadsheet to capture callback approval requests. The spreadsheet can contain any info you deem necessary for the approval request.

Here's an example spreadsheet:

The Approved column will be used to initiate a callback to the workflow.

Once the sheet is created, note the spreadsheet id that you will need in the workflow later. You can find the sheet id in the url of the spreadsheet:

Later, you will deploy the workflow with the default compute service account for simplicity. Find this service account email address by visiting IAM & Admin -> Service Accounts section of Google Cloud Console:

Make sure this service account has write permissions to the spreadsheet:

Create an Apps Script

Create an Apps Script to watch for the Approved column.

Go to Extensions and Apps Script in the spreadsheet. This opens up the App Script editor. Replace the default code in Code.gs with the code in Code.gs and press the Save button.

This code watches for changes for the Approved column. When it's set to TRUE, calls back workflow's callback URL with the approver information.

In App Script editor, go to Settings and check Show appsscript.json manifest file in editor. Replace the contents of appscript.json with appscript.json. This makes sure that the App Script has the required permissions.

Go to Triggers section and create a trigger from the sheet to the App Script when the sheet is edited:

Create a workflow

Create a workflow.yaml to run some initial steps, wait for the sheets callback and once received, run some more steps. Make sure you replace sheet id:

main:
  steps:
    - init:
        assign:
        # Replace with your sheetId and make sure the service account
        # for the workflow has write permissions to the sheet
        - sheetId: "10hieAH6b-oMeIVT_AerSLNxQck14IGhgi8ign-x2x8g"
    - before_sheets_callback:
        call: sys.log
        args:
          severity: INFO
          data: ${"Execute steps here before waiting for callback from sheets"}
    - wait_for_sheets_callback:
        call: await_callback_sheets
        args:
          sheetId: ${sheetId}
        result: await_callback_result
    - after_sheets_callback:
        call: sys.log
        args:
          severity: INFO
          data: ${"Execute steps here after receiving callback from sheets"}
    - returnResult:
        return: ${await_callback_result}

The await_callback_sheets sub-workflow receives a sheet id, creates a callback, saves the callback into to Google Sheets and waits for the callback:

await_callback_sheets:
    params: [sheetId]
    steps:
        - init:
            assign:
              - project_id: ${sys.get_env("GOOGLE_CLOUD_PROJECT_ID")}
              - location: ${sys.get_env("GOOGLE_CLOUD_LOCATION")}
              - workflow_id: ${sys.get_env("GOOGLE_CLOUD_WORKFLOW_ID")}
              - execution_id: ${sys.get_env("GOOGLE_CLOUD_WORKFLOW_EXECUTION_ID")}
        - create_callback:
            call: events.create_callback_endpoint
            args:
              http_callback_method: POST
            result: callback_details
        - save_callback_to_sheets:
            call: googleapis.sheets.v4.spreadsheets.values.append
            args:
                range: ${"Sheet1!A1:G1"}
                spreadsheetId: ${sheetId}
                valueInputOption: RAW
                body:
                    majorDimension: "ROWS"
                    values:
                      - ["${project_id}", "${location}", "${workflow_id}", "${execution_id}", "${callback_details.url}", "", "FALSE"]
        - log_and_await_callback:
            try:
              steps:
                - log_await_start:
                    call: sys.log
                    args:
                      severity: INFO
                      data: ${"Started waiting for callback from sheet " + sheetId}
                - await_callback:
                    call: events.await_callback
                    args:
                      callback: ${callback_details}
                      timeout: 3600
                    result: callback_request
                - log_await_stop:
                    call: sys.log
                    args:
                      severity: INFO
                      data: ${"Stopped waiting for callback from sheet " + sheetId}
            except:
                as: e
                steps:
                    - log_error:
                        call: sys.log
                        args:
                            severity: "ERROR"
                            text: ${"Received error " + e.message}
        - check_null_await_result:
            switch:
              - condition: ${callback_request == null}
                return: null
        - log_await_result:
            call: sys.log
            args:
              severity: INFO
              data: ${"Approved by " + callback_request.http_request.body.approver}
        - return_await_result:
            return: ${callback_request.http_request.body}

Deploy the workflow

Make sure you have a Google Cloud project and the project id is set in gcloud:

PROJECT_ID=your-project-id
gcloud config set project $PROJECT_ID

Run setup.sh to enable required services, grant necessary roles and deploy the workflow defined in workflow.yaml.

Run the workflow

You're now ready to test the end-to-end flow.

Run the workflow from Google Cloud Console or gcloud:

gcloud workflows run workflows-awaits-callback-sheets

You should see the workflow is in waiting state:

The logs also tell us that the workflow is waiting:

Info
2022-09-27 09:58:00.892 BST Execute steps here before waiting for callback from sheets
Info
2022-09-27 09:58:01.887 BST Started waiting for callback from sheet 10hieAH6b-oMeIVT_AerSLNxQck14IGhgi8ign-x2x8g

Go back to the sheet and you should also see the callback info appended by workflows with Approved column set to FALSE:

Now, add an approver name/email and change Approved colum to TRUE:

You should see the workflow is now succeeded:

The logs also tell us that the workflow is approved and completed:

Info
2022-09-27 10:04:11.101 BST Approved by Mete Atamel
Info
2022-09-27 10:04:11.442 BST Execute steps here after receiving callback from sheets