Change eager celery setting in local Docker (#1945)

[//]: # (Thank you for helping us out: your efforts mean great deal to the project and the community as a whole!)

[//]: # (Before you proceed:)

[//]: # (1. Make sure to add yourself to `CONTRIBUTORS.rst` through this PR provided you're contributing here for the first time)
[//]: # (2. Don't forget to update the `docs/` presuming others would benefit from a concise description of whatever that you're proposing)


## Description

[//]: # (What's it you're proposing?)

Added a note around CELERY_TASK_ALWAYS_EAGER = True in docker config for local development. This causes tasks to be executed on the 'main' thread rather than by the workers. I understand why that might be desirable, but thought it worth calling out incase (like me) it makes people think something is broken.


## Rationale

[//]: # (Why does the project need that?)

Ease of use/troubleshooting


## Use case(s) / visualization(s)

[//]: # ("Better to see something once than to hear about it a thousand times.")

CONTRIBUTORS.rst

@@ -180,6 +180,7 @@ Listed in alphabetical order.
   Denis Bobrov             `@delneg`_
   Philipp Matthies         `@canonnervio`_
   Vadim Iskuchekov         `@Egregors`_                 @egregors
+  Keith Bailey             `@keithjeb`_
 ========================== ============================ ==============
 
 .. _@a7p: https://github.com/a7p
@@ -297,6 +298,7 @@ Listed in alphabetical order.
 .. _@purplediane: https://github.com/purplediane
 .. _@umrashrf: https://github.com/umrashrf
 .. _@ahhda: https://github.com/ahhda
+.. _@keithjeb: https://github.com/keithjeb
 Special Thanks
 ~~~~~~~~~~~~~~
 

docs/developing-locally-docker.rst

@@ -171,6 +171,16 @@ When developing locally you can go with MailHog_ for email testing provided ``us
 
 .. _Mailhog: https://github.com/mailhog/MailHog/
 
+.. _`CeleryTasks`:
+
+Celery tasks in local development
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+When not using docker Celery tasks are set to run in Eager mode, so that a full stack is not needed. When using docker the task
+scheduler will be used by default.
+
+If you need tasks to be executed on the main thread during development set CELERY_TASK_ALWAYS_EAGER = True in config/settings/local.py.
+
+Possible uses could be for testing, or ease of profiling with DJDT.
 
 .. _`CeleryFlower`:
 

docs/developing-locally.rst

@@ -118,6 +118,16 @@ In production, we have Mailgun_ configured to have your back!
 .. _Mailgun: https://www.mailgun.com/
 
 
+Celery
+------
+If the project is configured to use Celery as a task scheduler then by default tasks are set to run on the main thread
+when developing locally. If you have the appropriate setup on your local machine then set
+
+CELERY_TASK_ALWAYS_EAGER = False
+
+in /config/settings/local.py
+
+
 Sass Compilation & Live Reloading
 ---------------------------------
 

{{cookiecutter.project_slug}}/config/settings/local.py

@@ -76,8 +76,10 @@ INSTALLED_APPS += ['django_extensions']  # noqa F405
 
 # Celery
 # ------------------------------------------------------------------------------
+{% if cookiecutter.use_docker == 'n' -%}
 # http://docs.celeryproject.org/en/latest/userguide/configuration.html#task-always-eager
 CELERY_TASK_ALWAYS_EAGER = True
+{%- endif %}
 # http://docs.celeryproject.org/en/latest/userguide/configuration.html#task-eager-propagates
 CELERY_TASK_EAGER_PROPAGATES = True