Stopping celery via upstart issues a TERM signal to the whole process group, which immediately kills the worker threads. This can lead to inconsistentcy in the state of a notification as an API call, for example, can take several seconds consequently the likelihood of the call being lost due to a restart is relatively high.
We need to ensure that we stop cleanly to ensure code deploys and autoscale events do not cause issues.
this script is called as part of a pre-stop hook in upstart, which passes a pid file location to the script. The script will then issues the TERM signal to only the master celery process. which will cleanly shut down the workers and exit.
the script will loop based on the existence of a /proc/{pid} for the celery master process. Once the file is gone the script will exit. Upstart blocks on this script before issuing kill on whatever processes may be left hanging around.
the length of the loop is a maximum 15 minutes - which is the tested max time a task may take. In reality it will exit much quicker.
notifications-api
Notifications api Application for the notification api.
Read and write notifications/status queue. Get and update notification status.
Setting Up
AWS credentials
To run the API you will need appropriate AWS credentials. You should receive these from whoever administrates your AWS account. Make sure you've got both an access key id and a secret access key.
Your aws credentials should be stored in a folder located at ~/.aws. Follow Amazon's instructions for storing them correctly.
### Virtualenv
mkvirtualenv -p /usr/local/bin/python3 notifications-api
### environment.sh
Creating the environment.sh file. Replace [unique-to-environment] with your something unique to the environment. Your AWS credentials should be set up for notify-tools (the development/CI AWS account).
Create a local environment.sh file containing the following:
echo "
export SQLALCHEMY_DATABASE_URI='postgresql://localhost/notification_api'
export SECRET_KEY='dev-notify-secret-key'
export DANGEROUS_SALT='dev-notify-salt'
export NOTIFY_ENVIRONMENT='development'
export ADMIN_CLIENT_SECRET='dev-notify-secret-key'
export ADMIN_BASE_URL='http://localhost:6012'
export FROM_NUMBER='development'
export MMG_URL='https://api.mmg.co.uk/json/api.php'
export MMG_API_KEY='MMG_API_KEY'
export LOADTESTING_API_KEY='FIRETEXT_SIMULATION_KEY'
export FIRETEXT_API_KEY='FIRETEXT_ACTUAL_KEY'
export STATSD_PREFIX='YOU_OWN_PREFIX'
export NOTIFICATION_QUEUE_PREFIX='YOUR_OWN_PREFIX'
export REDIS_URL="redis://localhost:6379/0"
"> environment.sh
NOTES:
- Replace the placeholder key and prefix values as appropriate
- The SECRET_KEY and DANGEROUS_SALT should match those in the notifications-admin app.
- The unique prefix for the queue names prevents clashing with others' queues in shared amazon environment and enables filtering by queue name in the SQS interface.
Postgres
Install Postgres.app. You will need admin on your machine to do this.
Redis
To switch redis on you'll need to install it locally. On a OSX we've used brew for this. To use redis caching you need to switch it on by changing the config for development:
REDIS_ENABLED = True
To run the application
First, run scripts/bootstrap.sh to install dependencies and create the databases.
You need to run the api application and a local celery instance.
There are two run scripts for running all the necessary parts.
scripts/run_app.sh
scripts/run_celery.sh
Optionally you can also run this script to run the scheduled tasks:
scripts/run_celery_beat.sh
To test the application
First, ensure that scripts/bootstrap.sh has been run, as it creates the test database.
Then simply run
make test
That will run pycodestyle for code analysis and our unit test suite. If you wish to run our functional tests, instructions can be found in the notifications-functional-tests repository.
To remove functional test data
NOTE: There is assumption that both the server name prefix and user name prefix are followed by a uuid. The script will search for all services/users with that prefix and only remove it if the prefix is followed by a uuid otherwise it will be skipped.
Locally
python application.py purge_functional_test_data -u <functional tests user name prefix> # Remove the user and associated services.
On the server
python server_commands.py purge_functional_test_data -u <functional tests user name prefix> # Remove the user and associated services.