This was introduced in #1811 as a way to avoid sending traffic to newly created apps where gunicorn had not started yet, such as the case during a scaling event. These days we depend mostly on scheduled scaling and we rarely need to scale above the scheduled values. Yesterday we had an event where (during a traffic spike) the healthcheck failed causing the instance to be killed and sending a 5XX response code to all the connections that this instance was handling at the time. However, this instance was not unhealthy and was serving traffic. The problem stems from a combination of using async workers, having to limit the number of database connections and a thread holding onto a db connection for the entire duration of the request. Specifically, we end up having requests queued up in gunicorn waiting for other requests to finish and release the db connection. Some pages such as the dashboard generate queries that can take >5s. If a healthcheck request is sent during a traffic spike and the instance in question was "unfortunate" enough to get handled a few of these long running queries, the healthcheck request will be queued up behind these slow requests and will fail to receive a response within 1s [docs]. Ideally we should be able to configure the healthcheck timeout to a value of our choosing, since we can end up in this situation again in the future. docs: https://docs.cloudfoundry.org/devguide/deploy-apps/healthchecks.html#types
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 NOTIFY_ENVIRONMENT='development'
export MMG_API_KEY='MMG_API_KEY'
export LOADTESTING_API_KEY='FIRETEXT_SIMULATION_KEY'
export FIRETEXT_API_KEY='FIRETEXT_ACTUAL_KEY'
export NOTIFICATION_QUEUE_PREFIX='YOUR_OWN_PREFIX'
export FLASK_APP=application.py
export FLASK_DEBUG=1
export WERKZEUG_DEBUG_PIN=off
"> 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 flake8 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 update application dependencies
requirements.txt file is generated from the requirements-app.txt in order to pin
versions of all nested dependencies. If requirements-app.txt has been changed (or
we want to update the unpinned nested dependencies) requirements.txt should be
regenerated with
make freeze-requirements
requirements.txt should be committed alongside requirements-app.txt changes.
To run one off tasks
Tasks are run through the flask command - run flask --help for more information. There are two sections we need to
care about: flask db contains alembic migration commands, and flask command contains all of our custom commands. For
example, to purge all dynamically generated functional test data, do the following:
Locally
flask command purge_functional_test_data -u <functional tests user name prefix>
On the server
cf run-task notify-api "flask command purge_functional_test_data -u <functional tests user name prefix>"
All commands and command options have a --help command if you need more information.
To create a new worker app
You need to:
- Create a new entry for your app in manifest-delivery-base.yml (example)
- Update the jenkins deployment job in the notifications-aws repo (example)
- Add the new worker's log group to the list of logs groups we get alerts about and we ship them to kibana (example)
- Optionally add it to the autoscaler (example)
Important:
Before pushing the deployment change on jenkins, read below about the first time deployment.
First time deployment of your new worker
Our deployment flow requires that the app is present in order to proceed with the deployment.
This means that the first deployment of your app must happen manually.
To do this:
- Ensure your code is backwards compatible
- From the root of this repo run
CF_APP=<APP_NAME> make <cf-space> cf-push
Once this is done, you can push your deployment changes to jenkins to have your app deployed on every deployment.