Workflows for orchestration in GCP - Mini Project: Build & Apply

Workflows for orchestration

📖 Scenario: You are building a simple workflow in Google Cloud Workflows to automate a daily task. This workflow will call two services in sequence: first, it will call a mock API to fetch data, then it will call another mock API to process that data.This project will guide you step-by-step to create the workflow definition in YAML format.

🎯 Goal: Create a Google Cloud Workflow YAML file that defines a sequence of two steps: fetchData and processData. Each step calls a mock HTTP endpoint. The workflow should be valid and deployable.

📋 What You'll Learn

Create a workflow named dailyTaskWorkflow with an initial step

Add a configuration variable for the base API URL

Define the fetchData step to call the /fetch endpoint

Define the processData step to call the /process endpoint using data from fetchData

💡 Why This Matters

🌍 Real World

Automating sequences of API calls is common in cloud environments to integrate services without manual intervention.

💼 Career

Understanding how to define and deploy workflows helps in roles like cloud engineer, DevOps, and site reliability engineering.

1

Create the initial workflow structure

Create a workflow YAML named dailyTaskWorkflow with a main sequence that starts with a step called fetchData. The fetchData step should be empty for now.

GCP

main:
  steps:
    - fetchData:
        # Your code here

Hint

Start by defining main with steps. Add a step named fetchData that calls http.get with empty arguments and stores the result in fetchResponse.

2

Add a configuration variable for the base API URL

Add a variable named baseUrl at the top level of the workflow and set it to "https://mockapi.example.com".

GCP

baseUrl: "https://mockapi.example.com"

main:
  steps:
    - fetchData:
        call: http.get
        args: {}
        result: fetchResponse
# Your code here

Hint

Define baseUrl as a top-level variable with the exact URL string.

3

Configure the fetchData step to call the fetch endpoint

Modify the fetchData step to call the URL ${baseUrl}/fetch using http.get. Pass the URL in args.url and store the result in fetchResponse.

GCP

baseUrl: "https://mockapi.example.com"

main:
  steps:
    - fetchData:
        call: http.get
        args:
          url: "${baseUrl}/fetch"
        result: fetchResponse
# Your code here

Hint

Use args.url to specify the full URL using the baseUrl variable and the /fetch path.

4

Add the processData step to call the process endpoint with fetched data

Add a new step named processData after fetchData in main.steps. It should call http.post with args.url set to ${baseUrl}/process and args.body set to fetchResponse.body. Store the result in processResponse.

GCP

baseUrl: "https://mockapi.example.com"

main:
  steps:
    - fetchData:
        call: http.get
        args:
          url: "${baseUrl}/fetch"
        result: fetchResponse
    - processData:
        # Your code here

Hint

Define processData step with call: http.post. Use args.url for the process endpoint and args.body to send the fetched data.

Practice

1. What is the main purpose of Google Cloud Workflows?

easy

A. To store large amounts of data securely

B. To automate and coordinate multiple cloud services in a sequence

C. To create virtual machines for computing

D. To monitor network traffic in real-time

Solution

1. Step 1: Understand the role of Workflows

   Workflows are designed to automate tasks by connecting different cloud services step-by-step.

2. Step 2: Compare options with this role

   Options B, C, and D describe storage, computing, and monitoring, which are not the main purpose of Workflows.

3. Final Answer:

   To automate and coordinate multiple cloud services in a sequence -> Option B

4. Quick Check:

   Workflows automate cloud tasks = A [OK]

Hint: Workflows connect services step-by-step to automate tasks [OK]

Common Mistakes:

• Confusing Workflows with storage or compute services
• Thinking Workflows monitor network traffic
• Assuming Workflows create virtual machines

2. Which of the following is the correct way to start a step in a Google Cloud Workflow YAML?

easy

A. steps:

B. start:

C. main:

D. execute:

Solution

1. Step 1: Recall the YAML structure for Workflows

   The main entry point for a workflow is defined under the main: key.

2. Step 2: Check other options

   Options like steps:, start:, and execute: are not valid top-level keys for starting a workflow.

3. Final Answer:

   main: -> Option C

4. Quick Check:

   Workflow starts with main: in YAML [OK]

Hint: Workflows start with main: block in YAML [OK]

Common Mistakes:

• Using steps: instead of main:
• Confusing start: as the entry point
• Trying execute: which is invalid

3. Given this snippet of a workflow YAML:

main:
  steps:
  - call: http.get
    args:
      url: "https://example.com/api"
  - return: ${steps[0].body.status}

What will the workflow return if the HTTP GET response body is {"status": "success"}?

medium

A. "success"

B. {"status": "success"}

C. An error because of wrong syntax

D. null

Solution

1. Step 1: Understand the call and return steps

   The first step calls an HTTP GET and stores the response in steps[0]. The second step returns the status field from the response body.

2. Step 2: Extract the status value from the response

   The response body is {"status": "success"}, so steps[0].body.status is "success".

3. Final Answer:

   "success" -> Option A

4. Quick Check:

   Return status field from HTTP response = "success" [OK]

Hint: Return uses ${steps[index].body.field} to get JSON values [OK]

Common Mistakes:

• Returning the whole body instead of the status field
• Syntax errors in accessing steps array
• Assuming null if not parsed correctly

4. Identify the error in this workflow snippet:

main:
  steps:
  - call: http.get
    args:
      url: "https://example.com/api"
  - return: steps[0].body.status

medium

A. Missing quotes around the URL

B. Incorrect indentation of steps

C. http.get is not a valid call

D. Missing ${} around the expression in return

Solution

1. Step 1: Check expression syntax in return

   In Workflows YAML, expressions must be wrapped in ${} to be evaluated.

2. Step 2: Verify other parts

   Indentation is correct, http.get is valid, and URL is quoted properly.

3. Final Answer:

   Missing ${} around the expression in return -> Option D

4. Quick Check:

   Expressions need ${} to evaluate in return [OK]

Hint: Wrap expressions in ${} to evaluate in workflow YAML [OK]

Common Mistakes:

• Forgetting ${} around expressions
• Misaligning YAML indentation
• Assuming http.get is invalid
• Not quoting URLs

5. You want to create a workflow that calls two APIs in sequence, but only calls the second API if the first returns status "ok". Which workflow feature helps you implement this conditional logic?

hard

A. Using switch or if steps to check the first API's response

B. Using parallel steps to call both APIs at the same time

C. Using retry to repeat the first API call until status is ok

D. Using return to stop the workflow after the first call

Solution

1. Step 1: Understand conditional execution in workflows

   Workflows support switch or if steps to decide which steps run based on conditions.

2. Step 2: Match the requirement

   To call the second API only if the first returns "ok", use if or switch to check the first response before proceeding.

3. Final Answer:

   Using switch or if steps to check the first API's response -> Option A

4. Quick Check:

   Conditional steps use if/switch to control flow [OK]

Hint: Use if or switch to run steps conditionally in workflows [OK]

Common Mistakes:

• Using parallel steps which run both APIs simultaneously
• Using retry which repeats calls but doesn't conditionally run next
• Using return which ends workflow early