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Execute a workflow by using client libraries

This quickstart shows you how to execute a workflow and view the execution results using a client library.

For more information about installing the client libraries and setting up your development environment, see the Workflows client libraries overview.

Before you begin

Some of the steps in this document might not work correctly if your organization applies constraints to your Google Cloud environment. In that case, you might not be able to complete tasks like creating public IP addresses or service account keys. If you make a request that returns an error about constraints, see how to Develop applications in a constrained Google Cloud environment.

  1. The sample in this quickstart assumes you have already deployed the workflow, myFirstWorkflow. If you haven't, deploy it now using the Google Cloud console or the Google Cloud CLI.
  2. Download and install the Git source code management tool.

Get the sample code

  1. Clone the sample app repository to your local machine:

    Java 

    git clone https://github.com/GoogleCloudPlatform/java-docs-samples.git

    Alternatively, you can download the sample as a zip file and extract it.

    Node.js 

    git clone https://github.com/GoogleCloudPlatform/nodejs-docs-samples.git

    Alternatively, you can download the sample as a zip file and extract it.

    Python 

    git clone https://github.com/GoogleCloudPlatform/python-docs-samples.git

    Alternatively, you can download the sample as a zip file and extract it.

  2. Change to the directory that contains the Workflows sample code:

    Java 

    cd java-docs-samples/workflows/cloud-client/

    Node.js 

    cd nodejs-docs-samples/workflows/quickstart/

    Python 

    cd python-docs-samples/workflows/cloud-client/

  3. Take a look at the sample code:

    Java

    workflows/cloud-client/src/main/java/com/example/workflows/WorkflowsQuickstart.java 
    
// Imports the Google Cloud client library

import com.google.cloud.workflows.executions.v1.CreateExecutionRequest;
import com.google.cloud.workflows.executions.v1.Execution;
import com.google.cloud.workflows.executions.v1.ExecutionsClient;
import com.google.cloud.workflows.executions.v1.WorkflowName;
import java.io.IOException;
import java.util.concurrent.ExecutionException;

public class WorkflowsQuickstart {

  private static final String PROJECT = System.getenv("GOOGLE_CLOUD_PROJECT");
  private static final String LOCATION = System.getenv().getOrDefault("LOCATION", "us-central1");
  private static final String WORKFLOW = System.getenv().getOrDefault("WORKFLOW",
      "myFirstWorkflow");

  public static void main(String... args)
      throws IOException, InterruptedException, ExecutionException {
    if (PROJECT == null) {
      throw new IllegalArgumentException(
        "Environment variable 'GOOGLE_CLOUD_PROJECT' is required to run this quickstart.");
    }
    workflowsQuickstart(PROJECT, LOCATION, WORKFLOW);
  }

  private static volatile boolean finished;

  public static void workflowsQuickstart(String projectId, String location, String workflow)
      throws IOException, InterruptedException, ExecutionException {
    // Initialize client that will be used to send requests. This client only needs
    // to be created once, and can be reused for multiple requests. After completing all of your
    // requests, call the "close" method on the client to safely clean up any remaining background
    // resources.
    try (ExecutionsClient executionsClient = ExecutionsClient.create()) {
      // Construct the fully qualified location path.
      WorkflowName parent = WorkflowName.of(projectId, location, workflow);

      // Creates the execution object.
      CreateExecutionRequest request =
          CreateExecutionRequest.newBuilder()
              .setParent(parent.toString())
              .setExecution(Execution.newBuilder().build())
              .build();
      Execution response = executionsClient.createExecution(request);

      String executionName = response.getName();
      System.out.printf("Created execution: %s%n", executionName);

      long backoffTime = 0;
      long backoffDelay = 1_000; // Start wait with delay of 1,000 ms
      final long backoffTimeout = 10 * 60 * 1_000; // Time out at 10 minutes
      System.out.println("Poll for results...");

      // Wait for execution to finish, then print results.
      while (!finished && backoffTime < backoffTimeout) {
        Execution execution = executionsClient.getExecution(executionName);
        finished = execution.getState() != Execution.State.ACTIVE;

        // If we haven't seen the results yet, wait.
        if (!finished) {
          System.out.println("- Waiting for results");
          Thread.sleep(backoffDelay);
          backoffTime += backoffDelay;
          backoffDelay *= 2; // Double the delay to provide exponential backoff.
        } else {
          System.out.println("Execution finished with state: " + execution.getState().name());
          System.out.println("Execution results: " + execution.getResult());
        }
      }
    }
  }
}

    Node.js

    workflows/quickstart/index.js 
    const {ExecutionsClient} = require('@google-cloud/workflows');
const client = new ExecutionsClient();

/**
 * TODO(developer): Uncomment these variables before running the sample.
 */
// const projectId = 'my-project';
// const location = 'us-central1';
// const workflow = 'myFirstWorkflow';

/**
 * Executes a Workflow and waits for the results with exponential backoff.
 * @param {string} projectId The Google Cloud Project containing the workflow
 * @param {string} location The workflow location
 * @param {string} workflow The workflow name
 */
async function executeWorkflow(projectId, location, workflow) {
  /**
   * Sleeps the process N number of milliseconds.
   * @param {Number} ms The number of milliseconds to sleep.
   */
  function sleep(ms) {
    return new Promise(resolve => {
      setTimeout(resolve, ms);
    });
  }

  // Execute workflow
  try {
    const createExecutionRes = await client.createExecution({
      parent: client.workflowPath(projectId, location, workflow),
    });
    const executionName = createExecutionRes[0].name;
    console.log(`Created execution: ${executionName}`);

    // Wait for execution to finish, then print results.
    let executionFinished = false;
    let backoffDelay = 1000; // Start wait with delay of 1,000 ms
    console.log('Poll every second for result...');
    while (!executionFinished) {
      const [execution] = await client.getExecution({
        name: executionName,
      });
      executionFinished = execution.state !== 'ACTIVE';

      // If we haven't seen the result yet, wait a second.
      if (!executionFinished) {
        console.log('- Waiting for results...');
        await sleep(backoffDelay);
        backoffDelay *= 2; // Double the delay to provide exponential backoff.
      } else {
        console.log(`Execution finished with state: ${execution.state}`);
        console.log(execution.result);
        return execution.result;
      }
    }
  } catch (e) {
    console.error(`Error executing workflow: ${e}`);
  }
}

executeWorkflow(projectId, location, workflowName).catch(err => {
  console.error(err.message);
  process.exitCode = 1;
});

    Python

    workflows/cloud-client/main.py 
    import time

from google.cloud import workflows_v1beta
from google.cloud.workflows import executions_v1beta
from google.cloud.workflows.executions_v1beta.types import executions

# TODO(developer): Uncomment these lines and replace with your values.
# project = 'my-project-id'
# location = 'us-central1'
# workflow = 'myFirstWorkflow'

if not project:
    raise Exception('GOOGLE_CLOUD_PROJECT env var is required.')

# Set up API clients.
execution_client = executions_v1beta.ExecutionsClient()
workflows_client = workflows_v1beta.WorkflowsClient()

# Construct the fully qualified location path.
parent = workflows_client.workflow_path(project, location, workflow)

# Execute the workflow.
response = execution_client.create_execution(request={"parent": parent})
print(f"Created execution: {response.name}")

# Wait for execution to finish, then print results.
execution_finished = False
backoff_delay = 1  # Start wait with delay of 1 second
print('Poll every second for result...')
while (not execution_finished):
    execution = execution_client.get_execution(request={"name": response.name})
    execution_finished = execution.state != executions.Execution.State.ACTIVE

    # If we haven't seen the result yet, wait a second.
    if not execution_finished:
        print('- Waiting for results...')
        time.sleep(backoff_delay)
        backoff_delay *= 2  # Double the delay to provide exponential backoff.
    else:
        print(f'Execution finished with state: {execution.state.name}')
        print(execution.result)
        return execution.result

The program does the following:

  1. Sets up the Cloud Client Libraries for Workflows.
  2. Executes a workflow.
  3. Polls the workflow's execution (using exponential backoff) until the execution terminates.
  4. Prints the execution results.

Run the sample

  1. To run the sample, first install dependencies:

    Java 

    mvn compile

    Node.js 

    npm install

    Python 

    pip3 install -r requirements.txt

  2. Run the script:

    Java 

    GOOGLE_CLOUD_PROJECT=PROJECT_ID LOCATION=CLOUD_REGION WORKFLOW=WORKFLOW_NAME mvn compile exec:java -Dexec.mainClass=com.example.workflows.WorkflowsQuickstart

    Node.js 

    node . PROJECT_ID CLOUD_REGION WORKFLOW_NAME

    Python 

    GOOGLE_CLOUD_PROJECT=PROJECT_ID LOCATION=CLOUD_REGION WORKFLOW=WORKFLOW_NAME python3 main.py

    Replace the following:

    • PROJECT_ID: (required) the Project ID of the Google Cloud project
    • CLOUD_REGION: the location for the workflow (default: us-central1)
    • WORKFLOW_NAME: the ID of the workflow (default: myFirstWorkflow)

    The output is similar to the following:

    Execution finished with state: SUCCEEDED
["Sunday","Sunday in the Park with George","Sunday shopping","Sunday Bloody Sunday","Sunday Times Golden Globe Race","Sunday All Stars","Sunday Night (South Korean TV series)","Sunday Silence","Sunday Without God","Sunday Independent (Ireland)"]

Clean up

To avoid incurring charges to your Google Cloud account for the resources used on this page, follow these steps.

  1. Go to the Workflows page in the Google Cloud console.
    Workflows

  2. From the list of workflows, click a workflow to go to its Workflow Details page.

  3. Click Delete.

  4. Type the name of the workflow and then click Confirm.

What's next