Hey guys,
Apache DolphinScheduler is a good tool for workflow scheduler, it’s
easy-to-extend,
distributed and have nice UI to create and maintain workflow. Our workflow only
support
define in UI, which is easy to use and user friendly, it’s good but could be
batter by
adding extend API and make workflow could define as code or yaml file. And
consider yaml
file it’s hard to maintain manually I think it better to use code to define it,
aka workflows-as-code.
When workflow definitions as code, we could easy to modify some configure
and do
some batch change for it. It’s could more easy to define similar task by loop
statement,
and it give ability adding unittest for workflow too. I hope Apache
DolphinScheduler could
combine the benefit of define by code and by UI, so I raise proposal for adding
workflows-as-code to Apache DolphinScheduler.
Actually, I already start it by adding POC PR[1]. In this PR, I adding
Python API give
user define workflow by Python code. This feature use *Py4J* connect Java and
Python,
which mean I never add any new database model and infra to Apache
DolphinScheduler,
I just reuse layer service in dolphinscheduler-api package to create workflow.
And we could
consider Python API just another interface for Apache DolphinScheduler, just
like our UI, it
allow we define and maintain workflow follow their rule.
Here it’s an tutorial workflow definitions by Python API, which you could
find it in PR file[2]
```python
from pydolphinscheduler.core.process_definition import ProcessDefinition
from pydolphinscheduler.tasks.shell import Shell
with ProcessDefinition(name="tutorial") as pd:
task_parent = Shell(name="task_parent", command="echo hello
pydolphinscheduler")
task_child_one = Shell(name="task_child_one", command="echo 'child one'")
task_child_two = Shell(name="task_child_two", command="echo 'child two'")
task_union = Shell(name="task_union", command="echo union")
task_group = [task_child_one, task_child_two]
task_parent.set_downstream(task_group)
task_union << task_group
pd.run()
```
In tutorial, we define a new ProcessDefinition named ‘tutorial’ using
python context,
and then we add four Shell tasks to ‘tutorial’, just five line we could create
one process
definition with four tasks.
Beside process definition and tasks, another think we have to
add to workflow it’s task dependent, we add function `set_downstream` and
`set_upstream`
to describe task dependent. At the same time, we overwrite bit operator and add
a shortcut
`>>` and `<<` to do it.
After dependent set, we done our workflow definition, but all definition are
in Python API
side, which mean it not persist to Apache DolphinScheduler database, and it
could not runs
by Apache DolphinScheduler until declare `pd.submit()` or directly run it by
`pd.run()`
[1]: https://github.com/apache/dolphinscheduler/pull/6269
<https://github.com/apache/dolphinscheduler/pull/6269>
[2]:
https://github.com/apache/dolphinscheduler/pull/6269/files#diff-5561fec6b57cc611bee2b0d8f030965d76bdd202801d9f8a1e2e74c21769bc41
<https://github.com/apache/dolphinscheduler/pull/6269/files#diff-5561fec6b57cc611bee2b0d8f030965d76bdd202801d9f8a1e2e74c21769bc41>
Best Wish
— Jiajie
