Use celery to send emails in background

DEVELOPMENT.md

@@ -69,6 +69,13 @@ Now, on your local machine, you should be able to navigate to
 `http://localhost:5000/admin` and login with the username "admin" with the
 password "admin".
 
+If you'd like to enable sending emails, you'll also need to run a celery worker
+with:
+
+```bash
+celery -A gavel:celery worker
+```
+
 **While developing, you should keep `vagrant rsync-auto` running on the host
 machine so that whenever you change any files, they're automatically synced
 over to the VM.** When the app running in the VM detects changed files, it'll

Procfile

@@ -1 +1,2 @@
+worker: celery -A gavel:celery worker
 web: python initialize.py && gunicorn gavel:app

README.md

@@ -69,10 +69,15 @@ gavel` (unless you're using a different database name). Before you use the app,
 you need to initialize the database by running `python initialize.py`. **Note
 that Gavel does not preserve database schema compatibility between versions.**
 
+In order to send emails, you'll need to install Redis.
+
 When testing, you can run the app with `python runserver.py`. In production,
 you should use something like [Gunicorn][gunicorn] to serve this. You can run
 the app with `gunicorn -b :<PORT> -w <number of workers> gavel:app`.
 
+For sending emails, you'll also need to start a celery worker with `celery -A
+gavel:celery worker`.
+
 ## Configuration
 
 Before starting the app, copy `config.template.yaml` to `config.yaml` and set

Vagrantfile

@@ -19,6 +19,7 @@ Vagrant.configure(2) do |config|
 
     apt-get install -y \
       postgresql-9.4 postgresql-server-dev-9.4 \
+      redis-server \
       python3-dev python3-pip
 
     pip3 install --upgrade pip

app.json

@@ -1,7 +1,18 @@
 {
     "addons": [
-        "heroku-postgresql:hobby-dev"
+        "heroku-postgresql:hobby-dev",
+        "heroku-redis:hobby-dev"
     ],
+    "formation": {
+        "web": {
+            "quantity": 1,
+            "size": "free"
+        },
+        "worker": {
+            "quantity": 1,
+            "size": "free"
+        }
+    },
     "description": "An awesome judging system for hackathons",
     "env": {
         "ADMIN_PASSWORD": "change-this-before-deploying",

config.template.yaml

@@ -46,6 +46,10 @@ secret_key: null
 # defaults to 'postgresql://localhost/gavel'
 db_uri: null
 
+# can also be specified as the 'REDIS_URL' or 'BROKER_URI' environment variable
+# defaults to 'redis://localhost:6379/0'
+broker_uri: null
+
 # can also be specified as the 'PORT' environment variable
 # defaults to '5000'
 port: null

gavel/__init__.py

@@ -23,6 +23,11 @@
 )
 assets.register('scss_all', scss)
 
+from celery import Celery
+app.config['CELERY_BROKER_URL'] = settings.BROKER_URI
+celery = Celery(app.name, broker=app.config['CELERY_BROKER_URL'])
+celery.conf.update(app.config)
+
 from gavel.models import db
 db.app = app
 db.init_app(app)

gavel/controllers/admin.py

@@ -235,4 +235,4 @@ def email_invite_links(annotators):
         body = '\n\n'.join(utils.get_paragraphs(raw_body))
         emails.append((annotator.email, settings.EMAIL_SUBJECT, body))
 
-    utils.send_emails(emails)
+    utils.send_emails.delay(emails)

gavel/settings.py

@@ -58,6 +58,7 @@ def _list(item):
 BASE_URL =            c.get('base_url',        'BASE_URL')
 ADMIN_PASSWORD =      c.get('admin_password',  'ADMIN_PASSWORD')
 DB_URI =              c.get('db_uri',          ['DATABASE_URL', 'DB_URI'], default='postgresql://localhost/gavel')
+BROKER_URI =          c.get('broker_uri',      ['REDIS_URL', 'BROKER_URI'], default='redis://localhost:6379/0')
 SECRET_KEY =          c.get('secret_key',      'SECRET_KEY')
 PORT =            int(c.get('port',            'PORT',                     default=5000))
 MIN_VIEWS =       int(c.get('min_views',       'MIN_VIEWS',                default=2))

gavel/utils.py

@@ -1,3 +1,4 @@
+from gavel import celery
 import gavel.settings as settings
 import gavel.crowd_bt as crowd_bt
 import gavel.constants as constants
@@ -50,6 +51,7 @@ def get_paragraphs(message):
     paragraphs = [i.replace('\n', ' ') for i in paragraphs if i]
     return paragraphs
 
+@celery.task
 def send_emails(emails):
     '''
     Send a batch of emails.

requirements.txt

@@ -1,4 +1,5 @@
 appdirs==1.4.3
+celery==4.0.2
 click==6.7
 Flask==0.12
 Flask-Assets==0.12
@@ -15,6 +16,7 @@ psycopg2==2.7.1
 pyparsing==2.2.0
 pyScss==1.3.5
 PyYAML==3.12
+redis==2.10.5
 requests==2.13.0
 scipy==0.19.0
 six==1.10.0