DolphinScheduler/dolphinscheduler-python/pydolphinscheduler/README.md

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# pydolphinscheduler

[![GitHub Build][ga-py-test]][ga]
[![Code style: black][black-shield]][black-gh]

pydolphinscheduler is python API for Apache DolphinScheduler, which allow you definition
your workflow by python code, aka workflow-as-codes.

## Quick Start

> **_Notice:_** For now, due to pydolphinscheduler without release to any binary tarball or [PyPI][pypi], you 
> have to clone Apache DolphinScheduler code from GitHub to ensure quick start setup

Here we show you how to install and run a simple example of pydolphinscheduler

### Prepare

```shell
# Clone code from github
git clone git@github.com:apache/dolphinscheduler.git

# Install pydolphinscheduler from source
cd dolphinscheduler-python/pydolphinscheduler
pip install -e .
```

### Start Server And Run Example

Before you run an example, you have to start backend server. You could follow [development setup][dev-setup]
section "DolphinScheduler Standalone Quick Start" to set up developer environment. You have to start backend
and frontend server in this step, which mean that you could view DolphinScheduler UI in your browser with URL
http://localhost:12345/dolphinscheduler

After backend server is being start, all requests from `pydolphinscheduler` would be sent to backend server.
And for now we could run a simple example by:

```shell
cd dolphinscheduler-python/pydolphinscheduler
python example/tutorial.py
```

> **_NOTICE:_** Since Apache DolphinScheduler's tenant is requests while running command, you might need to change
> tenant value in `example/tutorial.py`. For now the value is `tenant_exists`, please change it to username exists
> in you environment. 

After command execute, you could see a new project with single process definition named *tutorial* in the [UI][ui-project].

Until now, we finish quick start by an example of pydolphinscheduler and run it. If you want to inspect or join
pydolphinscheduler develop, you could take a look at [develop](#develop)

## Develop

pydolphinscheduler is python API for Apache DolphinScheduler, it just defines what workflow look like instead of
store or execute it. We here use [py4j][py4j] to dynamically access Java Virtual Machine.

### Setup Develop Environment

We already clone the code in [quick start](#quick-start), so next step we have to open pydolphinscheduler project
in you editor. We recommend you use [pycharm][pycharm] instead of [IntelliJ IDEA][idea] to open it. And you could
just open directory `dolphinscheduler-python/pydolphinscheduler` instead of `dolphinscheduler-python`.

Then you should add developer dependence to make sure you could run test and check code style locally

```shell
pip install -r requirements_dev.txt
```

### Brief Concept

Apache DolphinScheduler is design to define workflow by UI, and pydolphinscheduler try to define it by code. When
define by code, user usually do not care user, tenant, or queue exists or not. All user care about is created
a new workflow by the code his/her definition. So we have some **side object** in `pydolphinscheduler/side`
directory, their only check object exists or not, and create them if not exists. 

#### Process Definition

pydolphinscheduler workflow object name, process definition is also same name as Java object(maybe would be change to
other word for more simple).

#### Tasks

pydolphinscheduler tasks object, we use tasks to define exact job we want DolphinScheduler do for us. For now,
we only support `shell` task to execute shell task. [This link][all-task] list all tasks support in DolphinScheduler
and would be implemented in the further.

### Code Style

We use [Black][black] for code formatter and [Flake8][flake8] for pep8 checker. If you use [pycharm][pycharm]
or [IntelliJ IDEA][idea], maybe you could follow [Black-integration][black-editor] to configure them in your environment.

Our Python API CI would automatically run unittest when you submit pull request in GitHub, you could also run
static check locally.

```shell
# We recommend you run Black before Flake8, because Black could auto fix some code style issue
# but Flake8 just hint when code style not match pep8

# Run Black
black .

# Run Flake8
flake8
```

### Testing

pydolphinscheduler using [pytest][pytest] to test our codebase. GitHub Action will run our test when you create
pull request or commit to dev branch, with python version `3.6|3.7|3.8|3.9` and operating system `linux|macOS|windows`.

To test locally, you could directly run pytest after set `PYTHONPATH` 

```shell
PYTHONPATH=src/ pytest
```

<!-- content -->
[pypi]: https://pypi.org/
[dev-setup]: https://dolphinscheduler.apache.org/en-us/development/development-environment-setup.html
[ui-project]: http://8.142.34.29:12345/dolphinscheduler/ui/#/projects/list
[py4j]: https://www.py4j.org/index.html
[pycharm]: https://www.jetbrains.com/pycharm
[idea]: https://www.jetbrains.com/idea/
[all-task]: https://dolphinscheduler.apache.org/en-us/docs/dev/user_doc/guide/task/shell.html
[pytest]: https://docs.pytest.org/en/latest/
[black]: https://black.readthedocs.io/en/stable/index.html
[flake8]: https://flake8.pycqa.org/en/latest/index.html
[black-editor]: https://black.readthedocs.io/en/stable/integrations/editors.html#pycharm-intellij-idea
<!-- badge -->
[ga-py-test]: https://github.com/apache/dolphinscheduler/actions/workflows/py-ci.yml/badge.svg?branch=dev
[ga]: https://github.com/apache/dolphinscheduler/actions
[black-shield]: https://img.shields.io/badge/code%20style-black-000000.svg
[black-gh]: https://github.com/psf/black