
# Name
Component: Data preparation by executing an Apache Beam job in Cloud Dataflow

# Labels
Cloud Dataflow, Apache Beam, Kubeflow

# Summary
A Kubeflow pipeline component that prepares data by submitting an Apache Beam job (authored in Python) to Cloud Dataflow for execution. The Python Beam code is run with Cloud Dataflow Runner.

# Facets
<!--Make sure the asset has data for the following facets:
Use case
Technique
Input data type
ML workflow

The data must map to the acceptable values for these facets, as documented on the “taxonomy” sheet of go/aihub-facets
https://gitlab.aihub-content-external.com/aihubbot/kfp-components/commit/fe387ab46181b5d4c7425dcb8032cb43e70411c1
--->
Use case:
Other

Technique: 
Other

Input data type:
Tabular

ML workflow: 
Data preparation

# Details
## Intended use

Use this component to run a Python Beam code to submit a Cloud Dataflow job as a step of a Kubeflow pipeline. 

## Runtime arguments
Name | Description | Optional |  Data type| Accepted values | Default |
:--- | :----------| :----------| :----------| :----------| :---------- |
python_file_path |  The path to the Cloud Storage bucket or local directory containing the Python file to be run. | - |  GCSPath | - | - |
project_id |  The ID of the Google Cloud Platform (GCP) project  containing the Cloud Dataflow job.| -| GCPProjectID | -| -|
staging_dir  |   The path to the Cloud Storage directory where the staging files are stored. A random subdirectory will be created under the staging directory to keep the  job information.This is done so that you can resume the job in case of failure. The command line arguments, `staging_location` and `temp_location`, of the Beam code are passed through `staging_dir`. |   Yes  |   GCSPath  |  - |   None  |
requirements_file_path |   The path to the Cloud Storage bucket or local directory containing the pip requirements file. | Yes | GCSPath | - | None |
args |  The list of arguments to pass to the Python file. | No |  List | A list of string arguments | None |
wait_interval |  The number of seconds to wait between calls to get the status of the job. | Yes | Integer  | - | 30 |

## Input data schema

Before you use the component, the following files must be ready in a Cloud Storage bucket:
- A Beam Python code file.
- A  `requirements.txt` file which includes a list of dependent packages.

The Beam Python code should follow the [Beam programming guide](https://beam.apache.org/documentation/programming-guide/) as well as the following additional requirements to be compatible with this component:
- It accepts the command line arguments `--project`, `--temp_location`, `--staging_location`, which are [standard Dataflow Runner options](https://cloud.google.com/dataflow/docs/guides/specifying-exec-params#setting-other-cloud-pipeline-options).
- It enables `info logging` before the start of a Cloud Dataflow job in the Python code. This allows the component to track the status and ID of the job that is created. For example, calling `logging.getLogger().setLevel(logging.INFO)` before any other code.

## Output
Name | Description
:--- | :----------
job_id | The ID of the Cloud Dataflow job that is created.

## Cautions & requirements
To use the components, the following requirements must be met:
- Cloud Dataflow API is enabled.
- The component is running under a secret Kubeflow user service account in a Kubeflow Pipelines cluster.  For example:
    ```
    component_op(...).apply(gcp.use_gcp_secret('user-gcp-sa'))
    ```
The Kubeflow user service account is a member of:
- `roles/dataflow.developer` role of the project.
- `roles/storage.objectViewer` role of the Cloud Storage Objects `python_file_path` and `requirements_file_path`.
- `roles/storage.objectCreator` role of the Cloud Storage Object `staging_dir`. 

## Detailed description
The component does several things during the execution:
- Downloads `python_file_path` and `requirements_file_path` to local files.
- Starts a subprocess to launch the Python program.
- Monitors the logs produced from the subprocess to extract the Cloud Dataflow job information.
- Stores the Cloud Dataflow job information in `staging_dir` so the job can be resumed in case of failure.
- Waits for the job to finish.
The steps to use the component in a pipeline are:
1. Install the Kubeflow pipeline's SDK:

    ```python
    %%capture --no-stderr

    KFP_PACKAGE = 'https://storage.googleapis.com/ml-pipeline/release/0.1.14/kfp.tar.gz'
    !pip3 install $KFP_PACKAGE --upgrade
    ```

2. Load the component using the Kubeflow pipeline's SDK:

    ```python
    import kfp.components as comp

    dataflow_python_op = comp.load_component_from_url('https://raw.githubusercontent.com/kubeflow/pipelines/02c991dd265054b040265b3dfa1903d5b49df859/components/gcp/dataflow/launch_python/component.yaml')
    help(dataflow_python_op)
    ```

### Sample
The following sample code works in an IPython notebook or directly in Python code. See the sample code below to learn how to execute the template.
In this sample, we run a wordcount sample code in a Kubeflow pipeline. The output will be stored in a Cloud Storage bucket. Here is the sample code:

```python
!gsutil cat gs://ml-pipeline-playground/samples/dataflow/wc/wc.py
```
    
Concepts:
    
1. Reading data from text files.
2. Specifying inline transforms.
3. Counting a PCollection.
4. Writing data to Cloud Storage as text files.

Notes: 

To execute this pipeline locally, first edit the code to specify the output location. Output location could be a local file path or an output prefix on Cloud Storage. (Only update the output location marked with the first CHANGE comment in the following code.)
    
To execute this pipeline remotely, first edit the code to set your project ID, runner type, the staging location, the temp location, and the output location.
The specified Cloud Storage bucket(s) must already exist. (Update all the places marked with a CHANGE comment in the following code.)
    
Then, run the pipeline as described in the README. It will be deployed and run using the Cloud Dataflow service. No arguments are required to run the pipeline. You can see the results in your output bucket in the Cloud Storage browser.
    
```python
    from __future__ import absolute_import
    
    import argparse
    import logging
    import re
    
    from past.builtins import unicode
    
    import apache_beam as beam
    from apache_beam.io import ReadFromText
    from apache_beam.io import WriteToText
    from apache_beam.options.pipeline_options import PipelineOptions
    from apache_beam.options.pipeline_options import SetupOptions
    
    
    def run(argv=None):
      """Main entry point; defines and runs the wordcount pipeline."""
    
      parser = argparse.ArgumentParser()
      parser.add_argument('--input',
                          dest='input',
                          default='gs://dataflow-samples/shakespeare/kinglear.txt',
                          help='Input file to process.')
      parser.add_argument('--output',
                          dest='output',
                          # CHANGE 1/5: The Cloud Storage path is required
                          # to output the results.
                          default='gs://YOUR_OUTPUT_BUCKET/AND_OUTPUT_PREFIX',
                          help='Output file to write results to.')
      known_args, pipeline_args = parser.parse_known_args(argv)
      # pipeline_args.extend([
      #     # CHANGE 2/5: (OPTIONAL) Change this to DataflowRunner to
      #     # run your pipeline on the Cloud Dataflow Service.
      #     '--runner=DirectRunner',
      #     # CHANGE 3/5: Your project ID is required in order to run your pipeline on
      #     # the Cloud Dataflow Service.
      #     '--project=SET_YOUR_PROJECT_ID_HERE',
      #     # CHANGE 4/5: Your Cloud Storage path is required for staging local
      #     # files.
      #     '--staging_location=gs://YOUR_BUCKET_NAME/AND_STAGING_DIRECTORY',
      #     # CHANGE 5/5: Your Cloud Storage path is required for temporary
      #     # files.
      #     '--temp_location=gs://YOUR_BUCKET_NAME/AND_TEMP_DIRECTORY',
      #     '--job_name=your-wordcount-job',
      # ])
    
      # We use the save_main_session option because one or more DoFn's in this
      # workflow rely on global context (e.g., a module imported at module level).
      pipeline_options = PipelineOptions(pipeline_args)
      pipeline_options.view_as(SetupOptions).save_main_session = True
      with beam.Pipeline(options=pipeline_options) as p:
    
        # Read the text file[pattern] into a PCollection.
        lines = p | ReadFromText(known_args.input)
    
        # Count the occurrences of each word.
        counts = (
            lines
            | 'Split' >> (beam.FlatMap(lambda x: re.findall(r'[A-Za-z\']+', x))
                          .with_output_types(unicode))
            | 'PairWithOne' >> beam.Map(lambda x: (x, 1))
            | 'GroupAndSum' >> beam.CombinePerKey(sum))
    
        # Format the counts into a PCollection of strings.
        def format_result(word_count):
          (word, count) = word_count
          return '%s: %s' % (word, count)
    
        output = counts | 'Format' >> beam.Map(format_result)
    
        # Write the output using a "Write" transform that has side effects.
        # pylint: disable=expression-not-assigned
        output | WriteToText(known_args.output)
    
    
    if __name__ == '__main__':
      logging.getLogger().setLevel(logging.INFO)
      run()
```

#### Set sample parameters

```python
# Required parameters
PROJECT_ID = '<Put your project ID here>'
GCS_STAGING_DIR = 'gs://<Put your GCS path here>' # No ending slash
```

```python
# Optional parameters
EXPERIMENT_NAME = 'Dataflow - Launch Python'
OUTPUT_FILE = '{}/wc/wordcount.out'.format(GCS_STAGING_DIR)
```

#### Example pipeline that uses the component

```python
import kfp.dsl as dsl
import kfp.gcp as gcp
import json
@dsl.pipeline(
    name='Dataflow launch python pipeline',
    description='Dataflow launch python pipeline'
)
def pipeline(
    python_file_path = 'gs://ml-pipeline-playground/samples/dataflow/wc/wc.py',
    project_id = PROJECT_ID,
    staging_dir = GCS_STAGING_DIR,
    requirements_file_path = 'gs://ml-pipeline-playground/samples/dataflow/wc/requirements.txt',
    args = json.dumps([
        '--output', OUTPUT_FILE
    ]),
    wait_interval = 30
):
    dataflow_python_op(
        python_file_path = python_file_path, 
        project_id = project_id, 
        staging_dir = staging_dir, 
        requirements_file_path = requirements_file_path, 
        args = args,
        wait_interval = wait_interval).apply(gcp.use_gcp_secret('user-gcp-sa'))
```

#### Compile the pipeline

```python
pipeline_func = pipeline
pipeline_filename = pipeline_func.__name__ + '.zip'
import kfp.compiler as compiler
compiler.Compiler().compile(pipeline_func, pipeline_filename)
```

#### Submit the pipeline for execution

```python
#Specify values for the pipeline's arguments
arguments = {}

#Get or create an experiment
import kfp
client = kfp.Client()
experiment = client.create_experiment(EXPERIMENT_NAME)

#Submit a pipeline run
run_name = pipeline_func.__name__ + ' run'
run_result = client.run_pipeline(experiment.id, run_name, pipeline_filename, arguments)
```

#### Inspect the output

```python
!gsutil cat $OUTPUT_FILE
```

## References
* [Component Python code](https://github.com/kubeflow/pipelines/blob/master/components/gcp/container/component_sdk/python/kfp_component/google/dataflow/_launch_python.py)
* [Component Docker file](https://github.com/kubeflow/pipelines/blob/master/components/gcp/container/Dockerfile)
* [Sample notebook](https://github.com/kubeflow/pipelines/blob/master/components/gcp/dataflow/launch_python/sample.ipynb)
* [Dataflow Python Quickstart](https://cloud.google.com/dataflow/docs/quickstarts/quickstart-python)

## License
By deploying or using this software you agree to comply with the [AI Hub Terms of Service](https://aihub.cloud.google.com/u/0/aihub-tos) and the [Google APIs Terms of Service](https://developers.google.com/terms/). To the extent of a direct conflict of terms, the AI Hub Terms of Service will control.
