Currency alerting

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In this tutorial you will learn how to build a real-time streaming pipeline that sends push notifications to your phone when the Bitcoin price reaches a certain threshold.

Learning objectives

In this tutorial you will learn:

How to use an existing sample to interface Quix to a real-time event stream. In this tutorial this is a stream of trading data from CoinAPI.
How to create a transformation.
How to use an existing sample to interface Quix to a mobile device.

Getting help

If you need any help, please sign up to the Quix Community.

Prerequisites

To complete this tutorial you will need the following accounts:

Quix Cloud account - This enables you to create the real-time stream processing pipeline.

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CoinAPI - You can sign up for a free API key here. On the free tier, click the GET A FREE API KEY button, enter the requested information, and you will receive an email containing your API key. This enables you to access a stream of constantly updated BTC/USD exchange rate data.
Pushover - You can sign up for a free account here. Enter your details, and click Signup. You will receive a welcome email, and you can log in to Pushover to retrieve your user key and generate an API token. This enables you to send notifications to your phone. Install the Pushover mobile app from the Apple App store or Google Play.

The pipeline you will create

The objective of this tutorial is to create a pipeline that resembles the following example:

The colors describe the role of the microservice that is being deployed. The possible roles are as follows:

Source — enables streaming of data into Quix from any external source, such as an API or WebSocket.

Transformation — implements the processing of data, for example, cleaning data or implementing a Machine Learning (ML) model.

Destination — enables streaming of processed data to an external destination, such as a database or dashboard.

Setting up the CoinAPI source

In this section you will learn how to set up the source sample and deploy it in your pipeline as a microservice.

This sample, when deployed as a microservice in the Quix pipeline, connects a live stream of updates for the currency pair: BTC/USD. This real-time exchange rate data is streamed in from the CoinAPI through its WebSocket interface. The free sandbox version is used for the purposes of this tutorial.

To summarize this functionality:

The microservice streams the exchange rate data to a topic called currency-exchange-rates.
Downstream microservices in the pipeline can then read fom the currency-exchange-rates topic and process it in different ways. In this tutorial, you will check the current Bitcoin price against a threshold.

To set up the CoinAPI source, follow these steps:

In Quix, click the Code Samples icon in the main left-hand navigation.
In the search box on the Code Samples page, enter "CoinAPI - Exchange Rate Feed".

You will see the Coin API sample appear in the search results:

Click the Preview code button, and on the page that appears, click the Edit code button. When you choose to edit a sample, Quix prompts you to create a copy of it as an application, as sample are read-only.

Optionally, you could have clicked the Deploy button, which would have deployed the microservice directly. However, in this tutorial, you are given the opportunity to first look at the code, and modify it if necessary.

In the Setup form, configure the following environment variables:

Field	Value
`Name`	Enter an application name or keep the default suggestion.
`output`	Select the output topic. In this case, select `currency-exchange-rates` from the list.
`coin_api_key`	The API key that you use to access CoinAPI.
`asset_id_base`	The short code for the base currency that you want to track, for example BTC.
`asset_id_quote`	The short code for the target currency in which prices will be quoted, for example, USD.

Click Save as Application. You now have a copy of the CoinAPI sample in your environment.
Click the Deploy button. The sample is deployed as a service and automatically started.

Once the sample has been deployed, you’ll be redirected to the portal home page, where you can see the service in the pipeline context, as was illustrated previously.
Click the CoinAPI service card to inspect the logs:

A successful deployment will resemble the following example:

If there is an issue with the service, you can also inspect the build logs in the Lineage panel to check for any traces of a syntax error or other build issues.

Setting up the Threshold Alert transformation

In this section you will learn how to implement a microservice that will compare data in the BTC/USD exchange rate stream against a specific price threshold.

This microservice contains a simple algorithm that checks to see if a value has crossed a threshold in either direction.

The data stream is transformed from a series of real-time price points into a series of price alerts.

To summarize this functionality:

When the threshold criteria are met, the microservice writes an alert message to a topic called currency-rate-alerts.
Downstream services can then read fom this topic and send alerts and notifications whenever they detect a new message.

To set up the Threshold Alert sample, follow these steps:

Click on the Code Samples icon in the left-hand navigation.
In the search box on the Code Samples page, enter "Threshold Alerts".

You will see the Threshold Alert sample appear in the search results:
Click the Preview code button, and on the page that appears, click the Edit code button.

In the Setup application form, set the following environment variables:

Field	Value
`Name`	As usual, enter an application name or keep the default suggestion.
`input`	Select the input topic. In this case, select `currency-exchange-rates` from the list.
`output`	Select the output topic. In this case, select `currency-rate-alerts` from the list.
`parameterName`	Set this to `PRICE`.
`thresholdValue`	The price in USD that you'd like to get alerted about. For example, on the day that this tutorial was written, BTC was hovering around $16,300 so we entered `16300`. This increases the likelihood that some alerts are generated soon after deploying (otherwise it's hard to tell if it's working).
`msecs_before_recheck`	Enter the minimum delay in milliseconds between alerts. The default is 300 milliseconds (5 minutes), as this prevents numerous alerts when the price hovers around the threshold.

Click Save as Application.

You now have a copy of the Threshold Alert sample in your environment.
Click the Deploy button.

The sample is deployed as a service and automatically started. Once the microservice has been deployed, you'll be redirected to the pipeline view.
Click the Threshold Alert service card to inspect the logs.

A successful deployment will resemble the following screenshot:

In the Lineage panel, you will notice that the two services are connected by a line, which indicates that they're both using the same topic, currency-exchange-rates. The CoinAPI service is writing to currency-exchange-rates, and the Threshold Alert service is reading from it.

If there is an issue with the service, you can inspect the build logs in the Lineage panel, to check for any traces of a syntax error or other build issues.

Setting up the Pushover destination

In this section you create a destination microservice that sends a push notification when a threshold alert condition occurs.

This microservice reads from the currency-rate-alerts topic and whenever a new message arrives, it sends a push notification to the Pushover app on your mobile phone.

It also reads the contents of the message and enriches the notification with details on how the threshold was crossed, that is, whether the price is moving up or down.

To set up the push notification microservice, follow these steps:

Click on the Code Samples icon in the left-hand navigation.
In the search box on the Code Samples page, enter "Pushover".

You will see the Pushover Output sample appear in the search results:
Click the Preview code button, and on the page that appears, click the Edit code button.

On the Setup application page, complete the following fields:

Field	Value
`Name`	Enter an application name or keep the default suggestion.
`Input`	Select the input topic. In this case, select `currency-rate-alerts` from the list.Every message will be read from this topic, and turned into a push notification.
`base_url`	Leave the default value, `https://api.pushover.net/1/messages.json?`. If you decide to use another push notification app, your can always update this value.
`api_token`	Enter the API token that you generated for this application in your Pushover dashboard. For example: `azovmnbxxdxkj7j4g4wxxxdwf12xx4`.
`user_key`	Enter the user key that you received when you signed up with Pushover. For example: `u721txxxgmvuy5dxaxxxpzx5xxxx9e`

Click the Save as Application. You now have a copy of the Pushover notification sample in your environment.
Click the Deploy button.

You will now start receiving Pushover notifications on your phone, as shown here:

Depending on your threshold value and the price fluctuations, it might take a few minutes for you to get a notification. While you are waiting to receive a notification, you can inspect the logs, as shown previously.

Don't worry if the logs only show "Listening to Stream" initially — remember that the Threshold service only writes a message to the currency-rate-alerts topic when the threshold has been crossed.
This means that the currency-rate-alerts stream might be empty for a short while.
Depending on your threshold, it might take a couple of minutes for messages to start arriving.

You've now completed the tutorial.

Summary

Here's what you accomplished in this tutorial:

✅ You created a real-time web app, hosted on the Quix serverless compute environment.

✅ You deployed three real-time serverless microservices: the CoinAPI source to read data from another platform, the Threshold Alert transformation to make decisions based on that data, and the Pushover destination to send push notifications to your phone.

✅ You gained some experience in navigating Quix, and learned how to deploy microservices without needing to write any code.

Next steps

To learn more, try one of these tutorials:

Getting Help

If you need any help, please sign up to the Quix Community.