push-notifications

A service for sending push notification messages to Firebase Cloud Messaging (FCM), Apple Push Notifications Service (APNS) and to more push notifications vendors in the future.

Getting Started

Installation

First, clone the repository. Get the link from Gerrit or use the one from Github.

git clone [email protected]:wikimedia/mediawiki-services-push-notifications.git push-notifications-service

Install the dependencies

cd push-notifications
npm install

You are now ready to get to work!

• Inspect/modify/configure src/app.ts
• Add routes by placing files in src/routes/ (look at the files there for examples)
• The codebase for outgoing requests to push vendors lives under src/outgoing/{apns,fcm}
• The codebase for outgoing requests queueing lives under src/services/queueing.ts

For more information about the project you can read the push notification service documentation.

Build the project

Since this project is using TypeScript please run the build first before starting the service. To automatically rebuild the project and restart the service when the source code changes you can run:

npm run watch

Note: this does not happen when a file in the test folder changes.

Running the examples

The template is a fully-working example, so you may try it right away. To start the server hosting the REST API, simply run (inside the repo's directory)

npm start

This starts an HTTP server listening on localhost:8900. There are several routes you may query (with a browser, or curl and friends):

• http://localhost:8900/?doc
• http://localhost:8900/_info/
• http://localhost:8900/_info/name
• http://localhost:8900/_info/version
• http://localhost:8900/_info/home
• http://localhost:8900/{domain}/v1/siteinfo{/prop}
• http://localhost:8900/{domain}/v1/page/{title}
• http://localhost:8900/{domain}/v1/page/{title}/lead
• http://localhost:8900/ex/err/array
• http://localhost:8900/ex/err/file
• http://localhost:8900/ex/err/manual/error
• http://localhost:8900/ex/err/manual/deny
• http://localhost:8900/ex/err/auth
• http://localhost:8900/v1/message/fcm
• http://localhost:8900/v1/message/apns

All outgoing requests to push vendors support dryRun calls for local development.

For more information on the push backend implementations:

• APNS backend docs
• FCM backend docs

Push notifications flow

The service act as an abstraction layer to allow mediawiki and other services to send push notifications to users. Currently supported backends:

• Apple Push Notifications
• Firebase Cloud Messaging

The service API endpoints allows consumers to send notifications in a non-blocking way. Each worker initializes a queue that after a defined queue size or a timeout flushes the messages and send the notifications to the push providers in batches.

Token invalidation

On a failed response from the provider, if it indicates that the device token is not valid anymore, the service calls back to mediawiki API (meta.wikimedia.org) and unregisters the token from the user subscriptions.

Tests

The template also includes a small set of executable tests. To fire them up, simply run:

npm test

If you haven't changed anything in the code (and you have a working Internet connection), you should see all the tests passing. As testing most of the code is an important aspect of service development, there is also a bundled tool reporting the percentage of code covered. Start it with:

npm run-script coverage

Metrics

The service uses prometheus (directly) for exposing metrics. Here are the operational metrics we keep track of:

• Traffic (req/sec)
  • by HTTP method
  • by HTTP status
  • by endpoint
• Errors
  • Total
  • Current error rate
  • Current error %
• Latency
  • Total
    • by HTTP method
    • by HTTP status
    • by endpoint
  • Quantiles
    • by HTTP method
    • by HTTP status
    • by endpoint
• Saturation
  • Total CPU
  • Total memory
  • Total network
  • Avg CPU per container
  • Avg memory per container
  • Top 5 pods (network/memory/traffic)
  • Garbage collection (total, duration, quantiles)

On top of that we keep track of the following app metrics:

• Request duration handled by router in seconds
• Queue
  • Time the notification spent in the queue
  • Reported size of queue on flush
• FCM
  • Count of failed FCM notifications sent
  • Time spent on a transaction with the FCM service
  • Count of successful FCM notifications sent
• APNS
  • Time spent on a transaction with the APNS service
  • Count of successful APNS notifications sent
  • Count of failed APNS notifications sent

Deployment

Service is deployed in Kubernetes and the setup is maintained using helm.

• Here you can find more information about the deployment-charts that we use to maintain the Kubernetes setup.
• Here you can find more information on how to deploy a new version of the service.

Troubleshooting

In a lot of cases when there is an issue with node it helps to recreate the node_modules and dist directories:

rm -r node_modules dist
npm install
npm run build

Enjoy!