Event Queues¶

The FoundriesFactory API exposes everything about a Factory. In fact, app.foundries.io and fioctl are both built on top of that API. While this API is fully functional, it can be hard for certain operators to build their custom tooling for large numbers of devices if they must constantly poll the API for information. Event queues were designed to solve this issue.

Event queues provide a way for customers to receive messages about important events that are not easy to poll for. These include:

The first time a device connects to the device gateway.

When a device applies a configuration change.

When an OTA update starts and completes.

Event queues are implemented using Google PubSub to provide a well understood and tested framework. There are two types of event queues that can be created:

Push - Works as a webhook service. Events are sent to a managed URL where they can be processed.

Pull - Works like a typical message queue system where one can write their own client to receive and process events.

PubSub documentation includes a very useful guide to help decide which approach will work best for you. They also include a wide range of client libraries for consuming the Pull API. PubSub subscriptions are created with default retention, expiration, and acknowledgement values.

Implementation Details¶

Each FoundriesFactory is given a single PubSub Topic. Each Push and Pull queue created by a customer results in the creation of a PubSub Subscription. The FoundriesFactory API provides a thin, multi-tenant friendly wrapper to manage everything.

Note

For performance reasons, new push queues can take up to five minutes before they start receiving events.

Creating a Pull Queue¶

A pull queue can be created using fioctl:

# fioctl event-queues mk-pull <name> <where to save creds-file>
$ fioctl event-queues mk-pull docs-example $HOME/.fio-pull-queue.creds

Fioctl can also monitor this queue:

$ fioctl event-queues listen docs-example $HOME/.fio-pull-queue.creds

This command also serves as a reference example of how to implement a pull queue listener.

Creating a Push Queue¶

A push queue requires a little up front work:

Having an internet facing server to run the webhook service.

Authenticating incoming requests.

Quick Start Example¶

A great way to prototype a push queue is by using ngrok. This tool allows a service running on your laptop to be exposed via an ngrok reverse proxy. With ngrok installed, you can play with the example push queue code from your laptop:

# Start ngrok
$ ngrok http 8080
# make note of the "Forwarding                    https:..."
# This URL is required for the JWT_AUDIENCE below

# From another terminal:
# Install required python dependencies:
$ python3 -m venv /tmp/venv
$ /tmp/venv/bin/pip3 install cryptography requests pyjwt
$ JWT_AUDIENCE=<ngrok url> /tmp/venv/bin/python3 push_queue_example.py

Once the server is running, you can create a push queue with:

$ fioctl event-queues mk-push docs-push <ngrok URL from above>

At this point events will start showing up in the example server.

Push Queue Payloads¶

Incoming HTTP requests will look similar to:

{
 "message": {
   "attributes": {
     "event-type":"DEVICE_FIRST_SEEN"
   },
   "data":"aGVsbG9fd29ybGQ=",  # base64 encoded Event payload
   "messageId":"4292351872734735",
   "message_id":"4292351872734735",
   "publishTime":"2022-03-30T15:18:21.095Z",
   "publish_time":"2022-03-30T15:18:21.095Z"
 },
 "subscription":"projects/osf-prod/subscriptions/xxxxxxxx"
}

Push Queue Security¶

Incoming requests will include a header, Authorization: Bearer <jwt>. This JWT is signed with one of Google’s own private keys. The public keys are published online so that users can validate the signatures. The JWT audience header is set to the URL you specified when creating the push queue. The example push queue includes logic for validating this header.

Event Types¶

DEVICE_FIRST_SEEN¶

{
  "Uuid": <string: DEVICE_UUID>,
  "Time": <integer: unix seconds>
}

DEVICE_CONFIG_APPLIED¶

{
  "Uuid": <string: DEVICE_UUID>,
  "Time": <integer: unix seconds>
}

DEVICE_OTA_STARTED¶

{
  "Uuid": <string: DEVICE_UUID>,
  "Time": <integer: unix seconds>,
  "Target": <string: target name>,
  "Id": <string: update correlation-id> # works with `fioctl devices updates show <id>`
}

DEVICE_OTA_COMPLETED¶

{
  "Uuid": <string: DEVICE_UUID>,
  "Time": <integer: unix seconds>,
  "Target": <string: target name>,
  "Id": <string: update correlation-id>,
  "Success": <boolean>
}