際際滷

際際滷Share a Scribd company logo

Viewflow internals: ~3k sloc explaned

Mikhail Podgurskiy
Mikhail Podgurskiy

This document provides an overview of the Viewflow library, which is a reusable workflow library for Django applications. It discusses key aspects of Viewflow including flows, models, nodes, views, jobs, gates, activation, parallel task execution, error handling, and Viewsite for building user interfaces. Viewflow is designed to help separate CRUD operations from workflow logic and provides out-of-the-box support for Celery and other job queues to run tasks asynchronously. It aims to make it easy to build and grow business applications that involve people collaboration through workflows.

1 of 14
Downloaded 23 times
Viewflow internals 0.6.0 beta
Intro Reusable workflow library Django friendly Easy to start Helps to grow Business applications People collaboration
Intro Highly technical talk Dont panic. Library is only about 3k SLOC If anything unclear - ask kmmbvnr@gmail.com
Intro Flow Nodes This object Models Nodes Views Jobs Gates Activation Livecycle Parallel tasks execution Token Locking Error handling Activation context Viewsite Forms Viewflow internals
Flow CRUD and Flow Separation Task dependencies graph Boilerplate: Permissions, URLs
Models Process/Task tables Multi-table inheritance Abstract base classes
Views Function based Views Class based Views URL: <flow_cls>/<process_pk>/<task_name>/<task_pk>
Jobs Never miss the broken task Celery out of the box Easy to add another libraries support: rq, huye
Gates Workflow patterns support Decide what task should be executed next Easy to add logic by extending class or providing callable
Activation @classmethod def activate(cls, flow_task, prev_activation, token): def initialize(self, flow_task, task): def prepare(self, **data) def assign(self, user) def start(self) Weaves declarative Flow node with Process and Task instance def execute(self) def error(self, exc) def done(self) def activate_next(self)
Parallel task execution and Joins Task Token Split Node adds suffix Join Node waits all nodes with common prefix Short pessimistic locks @flow_view @flow_job Optimistic lock with django-fsm on Task OR If your are ok with fails Concurrent updates are rare, but:
Error handling View Jobs Any exception in subsequent task activation would rollback whole transaction. View task still available for user second try Job results committed immediately as job completes. Any exception in subsequent tasks activations would save subsequent task in error state. Could be customized by providing custom Activation class
Viewsite Completely optional, but you will like it Admin like speed for interface development Works with your Views Ready for end user Forms layouts, dynamic formsets, bootstrap More in next videos...
Thank you $ pip install django-viewflow http://viewflow.io http://github.com/kmmbvnr/django-viewflow/ kmmbvnr@gmail.com

More Related Content

Viewflow internals: ~3k sloc explaned

  • 2. Intro Reusable workflow library Django friendly Easy to start Helps to grow Business applications People collaboration
  • 3. Intro Highly technical talk Dont panic. Library is only about 3k SLOC If anything unclear - ask kmmbvnr@gmail.com
  • 4. Intro Flow Nodes This object Models Nodes Views Jobs Gates Activation Livecycle Parallel tasks execution Token Locking Error handling Activation context Viewsite Forms Viewflow internals
  • 5. Flow CRUD and Flow Separation Task dependencies graph Boilerplate: Permissions, URLs
  • 6. Models Process/Task tables Multi-table inheritance Abstract base classes
  • 7. Views Function based Views Class based Views URL: <flow_cls>/<process_pk>/<task_name>/<task_pk>
  • 8. Jobs Never miss the broken task Celery out of the box Easy to add another libraries support: rq, huye
  • 9. Gates Workflow patterns support Decide what task should be executed next Easy to add logic by extending class or providing callable
  • 10. Activation @classmethod def activate(cls, flow_task, prev_activation, token): def initialize(self, flow_task, task): def prepare(self, **data) def assign(self, user) def start(self) Weaves declarative Flow node with Process and Task instance def execute(self) def error(self, exc) def done(self) def activate_next(self)
  • 11. Parallel task execution and Joins Task Token Split Node adds suffix Join Node waits all nodes with common prefix Short pessimistic locks @flow_view @flow_job Optimistic lock with django-fsm on Task OR If your are ok with fails Concurrent updates are rare, but:
  • 12. Error handling View Jobs Any exception in subsequent task activation would rollback whole transaction. View task still available for user second try Job results committed immediately as job completes. Any exception in subsequent tasks activations would save subsequent task in error state. Could be customized by providing custom Activation class
  • 13. Viewsite Completely optional, but you will like it Admin like speed for interface development Works with your Views Ready for end user Forms layouts, dynamic formsets, bootstrap More in next videos...
  • 14. Thank you $ pip install django-viewflow http://viewflow.io http://github.com/kmmbvnr/django-viewflow/ kmmbvnr@gmail.com