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Relaynet's Proof of Concept

This monorepo implements a proof of concept of Twitter running on Relaynet. It allows you to post tweets like the one below and get the latest entries from your home timeline -- And thanks to the use of messaging, the server can simply push those updates without the app having to do polling.

You can also watch a demo of this PoC on YouTube.

This a Level 3 integration on the Relaynet Service Integration Scale: That is, a third party is running an adapter on top of the official Twitter API.

The Twitter app in this PoC isn't really a mobile app: It's a CLI.

Note that this PoC is not kept in sync with the latest changes to the Relaynet Protocol Suite Specifications.

Network diagram

The following network diagram illustrates the overall system:

The executables in this PoC match the nodes above: twitter-app, user-gateway, relay, relayer-gateway and twitter-api-adapter. Note that the endpoints are libraries, so they run in the same process as their corresponding apps.

In a production environment, the adapter's endpoint could run independently, perhaps as a reverse proxy or better yet: It could communicate with the adapter through a message broker like Amazon SQS or RabbitMQ.

This PoC (mostly) implements the following bindings:

  • CoSocket for cargo relay.
  • PoWebSocket for the internal parcel delivery connection (PDC) -- That is, the connection between the user gateway and the Twitter app endpoint.
  • PogRPC for the external PDC -- That is, the one between the relaying gateway and the adapter endpoint for the Twitter API.

Interactions

The interactions amongst the nodes in this service can be broken down into discrete processes:

Queueing messages from the Twitter app

The user may perform actions that will result in one or more messages:

Delivering messages to the Twitter app

An incoming cargo may contain parcels for different endpoints behind the same gateway. This is what happens with each parcel delivery:

Relaying cargo between gateways

The following diagram shows the interaction between a relayer and a gateway. Note that a single relaying gateway could serve multiple user gateways.

Delivering messages to the Twitter API adapter

In a production environment, the endpoint must retry the delivery of the message if the adapter doesn't acknowledge its receipt.

Delivering timeline updates

This is the process for getting timeline updates for each user that subscribes to this functionality via the Twitter app:

How to try the PoC

Setup

First of all, set up your environment:

  1. Make sure Node.js v10 and OpenSSL are available in your $PATH.
  2. Run npm install.
  3. Map twitter-3rd-party-endpoint.example.com to the local loopback (127.0.0.1). On Linux this can be done by adding an entry to /etc/hosts.
  4. Register an OAuth app on Twitter.
  5. Add a .env file to the root of the repo with the following content: 
    # From the Twitter OAuth app
TWITTER_CONSUMER_KEY='<your-consumer-key>'
TWITTER_CONSUMER_SECRET='<your-consumer-secret>'

# From the Twitter client
TWITTER_ACCESS_TOKEN_KEY='<your-access-token-key>'
TWITTER_ACCESS_TOKEN_SECRET='<your-access-token-secret>'

Running the PoC

At this point you're ready to see Relaynet in action.

First, you need to start the gateways and the Twitter API adapter by running npm start, which will run the three processes in the foreground. Keep this running in the foreground so you can see what the three processes are doing.

Next, open a new terminal session and try the following:

  1. Run bin/twitter-app to post a new tweet. The first time you run this, it will also create a message to subscribe the current app to updates to your home timeline. Subsequent calls will show any new tweets in your home timeline.

  2. Run bin/relay to simulate the exchange of cargo between the relayer and the user's gateway. Set the --cosocket option to the socket path where bin/user-gateway is listening. If you're using Linux, the exact command you need to run is:

    bin/relay \
    --cosocket=/tmp/user-gateway-data/cosocket.sock \
    --incoming=/tmp/usb-flashdrive/user-gw \
    --outgoing=/tmp/usb-flashdrive/relayer-gw

  3. Run bin/relay again, but this time to simulate the exchange of cargo between the relayer and their gateway. Make sure to set --cosocket to the relayer's gateway's socket path (output when you ran bin/relayer-gateway). If you're using Linux, the exact command you need to run is:

    bin/relay \
    --cosocket=/tmp/relayer-gateway-data/cosocket.sock \
    --incoming=/tmp/usb-flashdrive/relayer-gw \
    --outgoing=/tmp/usb-flashdrive/user-gw

  4. Go to twitter.com and check your account. You should find your tweet there.

Repeat the process above a few times, and you'll notice how the information flows in two directions: You're now able to send and receive data from Twitter.

Development tools

Have a look at bin-dev/ if you'd like to play with some lower level aspects of Relaynet.