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Simple pipeline

This guide walks you through a three-job data pipeline that fetches, processes, and publishes data on a schedule. You will learn how to define inputs, set up cron triggers, use environment variables, and chain jobs with dependencies.

Prerequisites​

Step 1: Understand the workflow​

This workflow defines a simple-pipeline that runs three jobs in sequence: fetch-data downloads and validates raw data, process transforms it, and publish makes the results available. Two cron schedules trigger the pipeline automatically at 6 AM and 6 PM UTC with different bucket configurations.

Step 2: Walk through the YAML​

Inputs​

The workflow defines two required string inputs: data_bucket and output_bucket. These are the UUIDs of your H2O Drive buckets.

inputs:
  data_bucket:
    type: string
    required: true
    description: "Source data bucket UUID"
  output_bucket:
    type: string
    required: true
    description: "Output data bucket UUID"

Inputs are typed parameters you pass at runtime or bind in triggers. See Inputs syntax reference for the full input schema.

Triggers​

The workflow uses two schedule entries, each providing its own input values:

trigger:
  schedule:
    - cron: "0 6 * * *"
      inputs:
        data_bucket: "f47ac10b-58cc-4372-a567-0e02b2c3d479"
        output_bucket: "8f4e3c2a-1b5d-4e8f-9a7c-6d3e2f1a0b9c"
    - cron: "0 18 * * *"
      inputs:
        data_bucket: "a1b2c3d4-e5f6-7890-1234-56789abcdef0"
        output_bucket: "b2c3d4e5-f6a7-8901-2345-6789abcdef01"

Each cron entry provides its own input values, so the same workflow runs against different buckets at different times — 6 AM against one set of buckets, 6 PM against another. See Triggers syntax reference.

Environment variables​

The env block maps input values to environment variables available across all jobs:

env:
  DATA_BUCKET: ${{ .inputs.data_bucket }}
  OUTPUT_BUCKET: ${{ .inputs.output_bucket }}
  SCRIPTS_REPO: "https://github.com/h2oai/data-pipeline"

The ${{ .inputs.data_bucket }} syntax is a Go template expression that resolves to the runtime input value. See Environment Variables and Expressions.

Jobs and dependencies​

The workflow defines three jobs that form a linear pipeline:

  • fetch-data — no dependencies, runs first.
  • process — depends on fetch-data, runs after it completes.
  • publish — depends on process, runs last.

Here is the process job definition:

process:
  name: Process data
  depends_on: [fetch-data]
  runner: cpu-large
  timeout: "1h"

Each job specifies a runner size to control compute resources and a timeout for maximum execution time. See Jobs syntax reference.

Steps​

Each job contains a sequence of steps. The fetch-data job uses three step types: download to fetch data from H2O Drive, run to execute shell commands, and upload to store results:

fetch-data:
  name: Fetch data from source
  runner: cpu-medium
  timeout: "30m"

  steps:
    - name: Download raw data
      download:
        source: drive://$DATA_BUCKET/raw-data/dataset.csv
        path: ./data/input.csv

    - name: Clone scripts
      run: git clone --depth 1 $SCRIPTS_REPO scripts

    - name: Install dependencies
      run: pip install -r scripts/requirements.txt

    - name: Validate data
      run: python scripts/validate.py --input data/input.csv

    - name: Upload validated data
      upload:
        path: data/input.csv
        destination: drive://$OUTPUT_BUCKET/validated/dataset.csv

See Steps syntax reference and Storage for full documentation on download, upload, and run step types.

Step 3: Deploy with the Python SDK​

Once you have the YAML file, use the Python SDK to create and activate the workflow:

import h2o_workflows

# Connect to H2O AI Cloud
clients = h2o_workflows.login()

# Read the workflow YAML
with open("examples/simple-pipeline.yaml") as f:
    source = f.read()

# Create the workflow in your workspace
from h2o_workflows.workflow.workflow import Workflow

workflow = clients.workflow.create_workflow(
    parent="workspaces/my-workspace",
    workflow=Workflow(source_contents=source),
)
print(f"Created: {workflow.name}")

# Activate the workflow to enable scheduled triggers
clients.workflow.activate_workflow(name=workflow.name)
print("Workflow activated -- triggers are now live")

This creates the workflow and activates it so the cron triggers start firing. For the full client API, see the Python SDK Reference.

Complete YAML​

id: simple-pipeline
name: Simple Pipeline

inputs:
  data_bucket:
    type: string
    required: true
    description: "Source data bucket UUID"

  output_bucket:
    type: string
    required: true
    description: "Output data bucket UUID"

trigger:
  schedule:
    - cron: "0 6 * * *"
      inputs:
        data_bucket: "f47ac10b-58cc-4372-a567-0e02b2c3d479"
        output_bucket: "8f4e3c2a-1b5d-4e8f-9a7c-6d3e2f1a0b9c"
    - cron: "0 18 * * *"
      inputs:
        data_bucket: "a1b2c3d4-e5f6-7890-1234-56789abcdef0"
        output_bucket: "b2c3d4e5-f6a7-8901-2345-6789abcdef01"

env:
  DATA_BUCKET: ${{ .inputs.data_bucket }}
  OUTPUT_BUCKET: ${{ .inputs.output_bucket }}
  SCRIPTS_REPO: "https://github.com/h2oai/data-pipeline"

jobs:
  fetch-data:
    name: Fetch data from source
    runner: cpu-medium
    timeout: "30m"

    steps:
      - name: Download raw data
        download:
          source: drive://$DATA_BUCKET/raw-data/dataset.csv
          path: ./data/input.csv

      - name: Clone scripts
        run: git clone --depth 1 $SCRIPTS_REPO scripts

      - name: Install dependencies
        run: pip install -r scripts/requirements.txt

      - name: Validate data
        run: python scripts/validate.py --input data/input.csv

      - name: Upload validated data
        upload:
          path: data/input.csv
          destination: drive://$OUTPUT_BUCKET/validated/dataset.csv

  process:
    name: Process data
    depends_on: [fetch-data]
    runner: cpu-large
    timeout: "1h"

    steps:
      - name: Download validated data
        download:
          source: drive://$OUTPUT_BUCKET/validated/dataset.csv
          path: ./data/input.csv

      - name: Clone scripts
        run: git clone --depth 1 $SCRIPTS_REPO scripts

      - name: Install dependencies
        run: pip install -r scripts/requirements.txt

      - name: Run processing
        run: python scripts/process.py --input data/input.csv --output data/output.csv

      - name: Upload processed data
        upload:
          path: data/output.csv
          destination: drive://$OUTPUT_BUCKET/processed/dataset.csv

  publish:
    name: Publish results
    depends_on: [process]
    runner: cpu-small
    timeout: "15m"

    steps:
      - name: Download processed data
        download:
          source: drive://$OUTPUT_BUCKET/processed/dataset.csv
          path: ./data/processed.csv

      - name: Clone scripts
        run: git clone --depth 1 $SCRIPTS_REPO scripts

      - name: Install dependencies
        run: pip install -r scripts/requirements.txt

      - name: Publish data
        run: python scripts/publish.py --input data/processed.csv

      - name: Upload final results
        upload:
          path: data/processed.csv
          destination: drive://$OUTPUT_BUCKET/published/dataset.csv

Next steps​

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Related content

Workflow inputs
Trigger configuration
Python SDK reference